This series removes drm_dev_unplug() and moves the unplugged state setting to drm_dev_unregister(). All drivers will now have access to the unplugged state if they so desire.
The drm_device ref handling wrt to the last fd closed after unregister have been simplified, which also fixed a double drm_dev_unregister() situation.
Noralf.
Noralf Trønnes (6): drm: Fix drm_release() and device unplug drm/drv: Prepare to remove drm_dev_unplug() drm/amd: Use drm_dev_unregister() drm/udl: Use drm_dev_unregister() drm/xen: Use drm_dev_unregister() drm/drv: Remove drm_dev_unplug()
drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c | 3 +- drivers/gpu/drm/drm_drv.c | 48 ++++++++----------------- drivers/gpu/drm/drm_file.c | 6 ++-- drivers/gpu/drm/udl/udl_drv.c | 3 +- drivers/gpu/drm/xen/xen_drm_front.c | 7 ++-- include/drm/drm_drv.h | 11 +++--- 6 files changed, 27 insertions(+), 51 deletions(-)
If userspace has open fd(s) when drm_dev_unplug() is run, it will result in drm_dev_unregister() being called twice. First in drm_dev_unplug() and then later in drm_release() through the call to drm_put_dev().
Since userspace already holds a ref on drm_device through the drm_minor, it's not necessary to add extra ref counting based on no open file handles. Instead just drm_dev_put() unconditionally in drm_dev_unplug().
We now has this: - Userpace holds a ref on drm_device as long as there's open fd(s) - The driver holds a ref on drm_device as long as it's bound to the struct device
When both sides are done with drm_device, it is released.
Signed-off-by: Noralf Trønnes noralf@tronnes.org --- drivers/gpu/drm/drm_drv.c | 6 +----- drivers/gpu/drm/drm_file.c | 6 ++---- 2 files changed, 3 insertions(+), 9 deletions(-)
diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c index 381581b01d48..05bbc2b622fc 100644 --- a/drivers/gpu/drm/drm_drv.c +++ b/drivers/gpu/drm/drm_drv.c @@ -376,11 +376,7 @@ void drm_dev_unplug(struct drm_device *dev) synchronize_srcu(&drm_unplug_srcu);
drm_dev_unregister(dev); - - mutex_lock(&drm_global_mutex); - if (dev->open_count == 0) - drm_dev_put(dev); - mutex_unlock(&drm_global_mutex); + drm_dev_put(dev); } EXPORT_SYMBOL(drm_dev_unplug);
diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c index 46f48f245eb5..3f20f598cd7c 100644 --- a/drivers/gpu/drm/drm_file.c +++ b/drivers/gpu/drm/drm_file.c @@ -479,11 +479,9 @@ int drm_release(struct inode *inode, struct file *filp)
drm_file_free(file_priv);
- if (!--dev->open_count) { + if (!--dev->open_count) drm_lastclose(dev); - if (drm_dev_is_unplugged(dev)) - drm_put_dev(dev); - } + mutex_unlock(&drm_global_mutex);
drm_minor_release(minor);
On 2/3/19 5:41 PM, Noralf Trønnes wrote:
If userspace has open fd(s) when drm_dev_unplug() is run, it will result in drm_dev_unregister() being called twice. First in drm_dev_unplug() and then later in drm_release() through the call to drm_put_dev().
Since userspace already holds a ref on drm_device through the drm_minor, it's not necessary to add extra ref counting based on no open file handles. Instead just drm_dev_put() unconditionally in drm_dev_unplug().
We now has this:
s/has/have ?
- Userpace holds a ref on drm_device as long as there's open fd(s)
- The driver holds a ref on drm_device as long as it's bound to the struct device
When both sides are done with drm_device, it is released.
Signed-off-by: Noralf Trønnes noralf@tronnes.org
Reviewed-by: Oleksandr Andrushchenko oleksandr_andrushchenko@epam.com
drivers/gpu/drm/drm_drv.c | 6 +----- drivers/gpu/drm/drm_file.c | 6 ++---- 2 files changed, 3 insertions(+), 9 deletions(-)
diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c index 381581b01d48..05bbc2b622fc 100644 --- a/drivers/gpu/drm/drm_drv.c +++ b/drivers/gpu/drm/drm_drv.c @@ -376,11 +376,7 @@ void drm_dev_unplug(struct drm_device *dev) synchronize_srcu(&drm_unplug_srcu);
drm_dev_unregister(dev);
- mutex_lock(&drm_global_mutex);
- if (dev->open_count == 0)
drm_dev_put(dev);- mutex_unlock(&drm_global_mutex);
- drm_dev_put(dev); } EXPORT_SYMBOL(drm_dev_unplug);
diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c index 46f48f245eb5..3f20f598cd7c 100644 --- a/drivers/gpu/drm/drm_file.c +++ b/drivers/gpu/drm/drm_file.c @@ -479,11 +479,9 @@ int drm_release(struct inode *inode, struct file *filp)
drm_file_free(file_priv);
- if (!--dev->open_count) {
- if (!--dev->open_count) drm_lastclose(dev);
if (drm_dev_is_unplugged(dev))drm_put_dev(dev);- }
mutex_unlock(&drm_global_mutex);
drm_minor_release(minor);
On Sun, Feb 03, 2019 at 04:41:55PM +0100, Noralf Trønnes wrote:
If userspace has open fd(s) when drm_dev_unplug() is run, it will result in drm_dev_unregister() being called twice. First in drm_dev_unplug() and then later in drm_release() through the call to drm_put_dev().
Since userspace already holds a ref on drm_device through the drm_minor, it's not necessary to add extra ref counting based on no open file handles. Instead just drm_dev_put() unconditionally in drm_dev_unplug().
We now has this:
- Userpace holds a ref on drm_device as long as there's open fd(s)
- The driver holds a ref on drm_device as long as it's bound to the struct device
When both sides are done with drm_device, it is released.
Signed-off-by: Noralf Trønnes noralf@tronnes.org
Reviewed-by: Sean Paul sean@poorly.run
drivers/gpu/drm/drm_drv.c | 6 +----- drivers/gpu/drm/drm_file.c | 6 ++---- 2 files changed, 3 insertions(+), 9 deletions(-)
diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c index 381581b01d48..05bbc2b622fc 100644 --- a/drivers/gpu/drm/drm_drv.c +++ b/drivers/gpu/drm/drm_drv.c @@ -376,11 +376,7 @@ void drm_dev_unplug(struct drm_device *dev) synchronize_srcu(&drm_unplug_srcu);
drm_dev_unregister(dev);
- mutex_lock(&drm_global_mutex);
- if (dev->open_count == 0)
drm_dev_put(dev);- mutex_unlock(&drm_global_mutex);
- drm_dev_put(dev);
} EXPORT_SYMBOL(drm_dev_unplug);
diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c index 46f48f245eb5..3f20f598cd7c 100644 --- a/drivers/gpu/drm/drm_file.c +++ b/drivers/gpu/drm/drm_file.c @@ -479,11 +479,9 @@ int drm_release(struct inode *inode, struct file *filp)
drm_file_free(file_priv);
- if (!--dev->open_count) {
- if (!--dev->open_count) drm_lastclose(dev);
if (drm_dev_is_unplugged(dev))drm_put_dev(dev);- }
mutex_unlock(&drm_global_mutex);
drm_minor_release(minor);
-- 2.20.1
The only thing now that makes drm_dev_unplug() special is that it sets drm_device->unplugged. Move this code to drm_dev_unregister() so that we can remove drm_dev_unplug().
Signed-off-by: Noralf Trønnes noralf@tronnes.org ---
Maybe s/unplugged/unregistered/ ?
I looked at drm_device->registered, but using that would mean that drm_dev_is_unplugged() would return before drm_device is registered. And given that its current purpose is to prevent race against connector registration, I stayed away from it.
Noralf.
drivers/gpu/drm/drm_drv.c | 27 +++++++++++++++------------ include/drm/drm_drv.h | 10 ++++------ 2 files changed, 19 insertions(+), 18 deletions(-)
diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c index 05bbc2b622fc..e0941200edc6 100644 --- a/drivers/gpu/drm/drm_drv.c +++ b/drivers/gpu/drm/drm_drv.c @@ -366,15 +366,6 @@ EXPORT_SYMBOL(drm_dev_exit); */ void drm_dev_unplug(struct drm_device *dev) { - /* - * After synchronizing any critical read section is guaranteed to see - * the new value of ->unplugged, and any critical section which might - * still have seen the old value of ->unplugged is guaranteed to have - * finished. - */ - dev->unplugged = true; - synchronize_srcu(&drm_unplug_srcu); - drm_dev_unregister(dev); drm_dev_put(dev); } @@ -832,11 +823,14 @@ EXPORT_SYMBOL(drm_dev_register); * drm_dev_register() but does not deallocate the device. The caller must call * drm_dev_put() to drop their final reference. * - * A special form of unregistering for hotpluggable devices is drm_dev_unplug(), - * which can be called while there are still open users of @dev. + * This function can be called while there are still open users of @dev as long + * as the driver protects its device resources using drm_dev_enter() and + * drm_dev_exit(). * * This should be called first in the device teardown code to make sure - * userspace can't access the device instance any more. + * userspace can't access the device instance any more. Drivers that support + * device unplug will probably want to call drm_atomic_helper_shutdown() first + * in order to disable the hardware on regular driver module unload. */ void drm_dev_unregister(struct drm_device *dev) { @@ -845,6 +839,15 @@ void drm_dev_unregister(struct drm_device *dev) if (drm_core_check_feature(dev, DRIVER_LEGACY)) drm_lastclose(dev);
+ /* + * After synchronizing any critical read section is guaranteed to see + * the new value of ->unplugged, and any critical section which might + * still have seen the old value of ->unplugged is guaranteed to have + * finished. + */ + dev->unplugged = true; + synchronize_srcu(&drm_unplug_srcu); + dev->registered = false;
drm_client_dev_unregister(dev); diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h index ca46a45a9cce..c50696c82a42 100644 --- a/include/drm/drm_drv.h +++ b/include/drm/drm_drv.h @@ -736,13 +736,11 @@ void drm_dev_unplug(struct drm_device *dev); * drm_dev_is_unplugged - is a DRM device unplugged * @dev: DRM device * - * This function can be called to check whether a hotpluggable is unplugged. - * Unplugging itself is singalled through drm_dev_unplug(). If a device is - * unplugged, these two functions guarantee that any store before calling - * drm_dev_unplug() is visible to callers of this function after it completes + * This function can be called to check whether @dev is unregistered. This can + * be used to detect that the underlying parent device is gone. * - * WARNING: This function fundamentally races against drm_dev_unplug(). It is - * recommended that drivers instead use the underlying drm_dev_enter() and + * WARNING: This function fundamentally races against drm_dev_unregister(). It + * is recommended that drivers instead use the underlying drm_dev_enter() and * drm_dev_exit() function pairs. */ static inline bool drm_dev_is_unplugged(struct drm_device *dev)
On 2/3/19 5:41 PM, Noralf Trønnes wrote:
The only thing now that makes drm_dev_unplug() special is that it sets drm_device->unplugged. Move this code to drm_dev_unregister() so that we can remove drm_dev_unplug().
Signed-off-by: Noralf Trønnes noralf@tronnes.org
Reviewed-by: Oleksandr Andrushchenko oleksandr_andrushchenko@epam.com
Maybe s/unplugged/unregistered/ ?
I looked at drm_device->registered, but using that would mean that drm_dev_is_unplugged() would return before drm_device is registered. And given that its current purpose is to prevent race against connector registration, I stayed away from it.
Noralf.
drivers/gpu/drm/drm_drv.c | 27 +++++++++++++++------------ include/drm/drm_drv.h | 10 ++++------ 2 files changed, 19 insertions(+), 18 deletions(-)
diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c index 05bbc2b622fc..e0941200edc6 100644 --- a/drivers/gpu/drm/drm_drv.c +++ b/drivers/gpu/drm/drm_drv.c @@ -366,15 +366,6 @@ EXPORT_SYMBOL(drm_dev_exit); */ void drm_dev_unplug(struct drm_device *dev) {
- /*
* After synchronizing any critical read section is guaranteed to see* the new value of ->unplugged, and any critical section which might* still have seen the old value of ->unplugged is guaranteed to have* finished.*/- dev->unplugged = true;
- synchronize_srcu(&drm_unplug_srcu);
- drm_dev_unregister(dev); drm_dev_put(dev); }
@@ -832,11 +823,14 @@ EXPORT_SYMBOL(drm_dev_register);
- drm_dev_register() but does not deallocate the device. The caller must call
- drm_dev_put() to drop their final reference.
- A special form of unregistering for hotpluggable devices is drm_dev_unplug(),
- which can be called while there are still open users of @dev.
- This function can be called while there are still open users of @dev as long
- as the driver protects its device resources using drm_dev_enter() and
- drm_dev_exit().
- This should be called first in the device teardown code to make sure
- userspace can't access the device instance any more.
- userspace can't access the device instance any more. Drivers that support
- device unplug will probably want to call drm_atomic_helper_shutdown() first
*/ void drm_dev_unregister(struct drm_device *dev) {
- in order to disable the hardware on regular driver module unload.
@@ -845,6 +839,15 @@ void drm_dev_unregister(struct drm_device *dev) if (drm_core_check_feature(dev, DRIVER_LEGACY)) drm_lastclose(dev);
/*
* After synchronizing any critical read section is guaranteed to see* the new value of ->unplugged, and any critical section which might* still have seen the old value of ->unplugged is guaranteed to have* finished.*/dev->unplugged = true;
synchronize_srcu(&drm_unplug_srcu);
dev->registered = false;
drm_client_dev_unregister(dev);
diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h index ca46a45a9cce..c50696c82a42 100644 --- a/include/drm/drm_drv.h +++ b/include/drm/drm_drv.h @@ -736,13 +736,11 @@ void drm_dev_unplug(struct drm_device *dev);
- drm_dev_is_unplugged - is a DRM device unplugged
- @dev: DRM device
- This function can be called to check whether a hotpluggable is unplugged.
- Unplugging itself is singalled through drm_dev_unplug(). If a device is
- unplugged, these two functions guarantee that any store before calling
- drm_dev_unplug() is visible to callers of this function after it completes
- This function can be called to check whether @dev is unregistered. This can
- be used to detect that the underlying parent device is gone.
- WARNING: This function fundamentally races against drm_dev_unplug(). It is
- recommended that drivers instead use the underlying drm_dev_enter() and
- WARNING: This function fundamentally races against drm_dev_unregister(). It
*/ static inline bool drm_dev_is_unplugged(struct drm_device *dev)
- is recommended that drivers instead use the underlying drm_dev_enter() and
- drm_dev_exit() function pairs.
On Sun, Feb 03, 2019 at 04:41:56PM +0100, Noralf Trønnes wrote:
The only thing now that makes drm_dev_unplug() special is that it sets drm_device->unplugged. Move this code to drm_dev_unregister() so that we can remove drm_dev_unplug().
Signed-off-by: Noralf Trønnes noralf@tronnes.org
Maybe s/unplugged/unregistered/ ?
I looked at drm_device->registered, but using that would mean that drm_dev_is_unplugged() would return before drm_device is registered. And given that its current purpose is to prevent race against connector registration, I stayed away from it.
Yeah I think we need to keep the registered state separate from unplugged. Iirc this exact scenario is what we discussed when you revamped the unplug infrastructure.
Noralf.
drivers/gpu/drm/drm_drv.c | 27 +++++++++++++++------------ include/drm/drm_drv.h | 10 ++++------ 2 files changed, 19 insertions(+), 18 deletions(-)
diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c index 05bbc2b622fc..e0941200edc6 100644 --- a/drivers/gpu/drm/drm_drv.c +++ b/drivers/gpu/drm/drm_drv.c @@ -366,15 +366,6 @@ EXPORT_SYMBOL(drm_dev_exit); */ void drm_dev_unplug(struct drm_device *dev) {
- /*
* After synchronizing any critical read section is guaranteed to see* the new value of ->unplugged, and any critical section which might* still have seen the old value of ->unplugged is guaranteed to have* finished.*/- dev->unplugged = true;
- synchronize_srcu(&drm_unplug_srcu);
- drm_dev_unregister(dev); drm_dev_put(dev);
} @@ -832,11 +823,14 @@ EXPORT_SYMBOL(drm_dev_register);
- drm_dev_register() but does not deallocate the device. The caller must call
- drm_dev_put() to drop their final reference.
- A special form of unregistering for hotpluggable devices is drm_dev_unplug(),
- which can be called while there are still open users of @dev.
- This function can be called while there are still open users of @dev as long
- as the driver protects its device resources using drm_dev_enter() and
- drm_dev_exit().
- This should be called first in the device teardown code to make sure
- userspace can't access the device instance any more.
- userspace can't access the device instance any more. Drivers that support
- device unplug will probably want to call drm_atomic_helper_shutdown() first
Read once more with a bit more coffee, spotted this:
s/first/afterwards/ - shutting down the hw before we've taken it away from userspace is kinda the wrong way round. It should be the inverse of driver load, which is 1) allocate structures 2) prep hw 3) register driver with the world (simplified ofc).
*/
- in order to disable the hardware on regular driver module unload.
void drm_dev_unregister(struct drm_device *dev) { @@ -845,6 +839,15 @@ void drm_dev_unregister(struct drm_device *dev) if (drm_core_check_feature(dev, DRIVER_LEGACY)) drm_lastclose(dev);
/*
* After synchronizing any critical read section is guaranteed to see* the new value of ->unplugged, and any critical section which might* still have seen the old value of ->unplugged is guaranteed to have* finished.*/dev->unplugged = true;
synchronize_srcu(&drm_unplug_srcu);
dev->registered = false;
drm_client_dev_unregister(dev);
diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h index ca46a45a9cce..c50696c82a42 100644 --- a/include/drm/drm_drv.h +++ b/include/drm/drm_drv.h @@ -736,13 +736,11 @@ void drm_dev_unplug(struct drm_device *dev);
- drm_dev_is_unplugged - is a DRM device unplugged
- @dev: DRM device
- This function can be called to check whether a hotpluggable is unplugged.
- Unplugging itself is singalled through drm_dev_unplug(). If a device is
- unplugged, these two functions guarantee that any store before calling
- drm_dev_unplug() is visible to callers of this function after it completes
- This function can be called to check whether @dev is unregistered. This can
- be used to detect that the underlying parent device is gone.
I think it'd be good to keep the first part, and just update the reference to drm_dev_unregister. So:
* This function can be called to check whether a hotpluggable is unplugged. * Unplugging itself is singalled through drm_dev_unregister(). If a device is * unplugged, these two functions guarantee that any store before calling * drm_dev_unregister() is visible to callers of this function after it * completes.
I think your version shrugs a few important details under the rug. With those nits addressed:
Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch
Cheers, Daniel
- WARNING: This function fundamentally races against drm_dev_unplug(). It is
- recommended that drivers instead use the underlying drm_dev_enter() and
- WARNING: This function fundamentally races against drm_dev_unregister(). It
*/
- is recommended that drivers instead use the underlying drm_dev_enter() and
- drm_dev_exit() function pairs.
static inline bool drm_dev_is_unplugged(struct drm_device *dev)
2.20.1
Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx
Den 04.02.2019 16.41, skrev Daniel Vetter:
On Sun, Feb 03, 2019 at 04:41:56PM +0100, Noralf Trønnes wrote:
The only thing now that makes drm_dev_unplug() special is that it sets drm_device->unplugged. Move this code to drm_dev_unregister() so that we can remove drm_dev_unplug().
Signed-off-by: Noralf Trønnes noralf@tronnes.org
[...]
drivers/gpu/drm/drm_drv.c | 27 +++++++++++++++------------ include/drm/drm_drv.h | 10 ++++------ 2 files changed, 19 insertions(+), 18 deletions(-)
diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c index 05bbc2b622fc..e0941200edc6 100644 --- a/drivers/gpu/drm/drm_drv.c +++ b/drivers/gpu/drm/drm_drv.c @@ -366,15 +366,6 @@ EXPORT_SYMBOL(drm_dev_exit); */ void drm_dev_unplug(struct drm_device *dev) {
- /*
* After synchronizing any critical read section is guaranteed to see* the new value of ->unplugged, and any critical section which might* still have seen the old value of ->unplugged is guaranteed to have* finished.*/- dev->unplugged = true;
- synchronize_srcu(&drm_unplug_srcu);
- drm_dev_unregister(dev); drm_dev_put(dev);
} @@ -832,11 +823,14 @@ EXPORT_SYMBOL(drm_dev_register);
- drm_dev_register() but does not deallocate the device. The caller must call
- drm_dev_put() to drop their final reference.
- A special form of unregistering for hotpluggable devices is drm_dev_unplug(),
- which can be called while there are still open users of @dev.
- This function can be called while there are still open users of @dev as long
- as the driver protects its device resources using drm_dev_enter() and
- drm_dev_exit().
- This should be called first in the device teardown code to make sure
- userspace can't access the device instance any more.
- userspace can't access the device instance any more. Drivers that support
- device unplug will probably want to call drm_atomic_helper_shutdown() first
Read once more with a bit more coffee, spotted this:
s/first/afterwards/ - shutting down the hw before we've taken it away from userspace is kinda the wrong way round. It should be the inverse of driver load, which is 1) allocate structures 2) prep hw 3) register driver with the world (simplified ofc).
The problem is that drm_dev_unregister() sets the device as unplugged and if drm_atomic_helper_shutdown() is called afterwards it's not allowed to touch hardware.
I know it's the wrong order, but the only way to do it in the right order is to have a separate function that sets unplugged:
drm_dev_unregister(); drm_atomic_helper_shutdown(); drm_dev_set_unplugged();
Noralf.
*/
- in order to disable the hardware on regular driver module unload.
void drm_dev_unregister(struct drm_device *dev) { @@ -845,6 +839,15 @@ void drm_dev_unregister(struct drm_device *dev) if (drm_core_check_feature(dev, DRIVER_LEGACY)) drm_lastclose(dev);
/*
* After synchronizing any critical read section is guaranteed to see* the new value of ->unplugged, and any critical section which might* still have seen the old value of ->unplugged is guaranteed to have* finished.*/dev->unplugged = true;
synchronize_srcu(&drm_unplug_srcu);
dev->registered = false;
drm_client_dev_unregister(dev);
diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h index ca46a45a9cce..c50696c82a42 100644 --- a/include/drm/drm_drv.h +++ b/include/drm/drm_drv.h @@ -736,13 +736,11 @@ void drm_dev_unplug(struct drm_device *dev);
- drm_dev_is_unplugged - is a DRM device unplugged
- @dev: DRM device
- This function can be called to check whether a hotpluggable is unplugged.
- Unplugging itself is singalled through drm_dev_unplug(). If a device is
- unplugged, these two functions guarantee that any store before calling
- drm_dev_unplug() is visible to callers of this function after it completes
- This function can be called to check whether @dev is unregistered. This can
- be used to detect that the underlying parent device is gone.
I think it'd be good to keep the first part, and just update the reference to drm_dev_unregister. So:
- This function can be called to check whether a hotpluggable is unplugged.
- Unplugging itself is singalled through drm_dev_unregister(). If a device is
- unplugged, these two functions guarantee that any store before calling
- drm_dev_unregister() is visible to callers of this function after it
- completes.
I think your version shrugs a few important details under the rug. With those nits addressed:
Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch
Cheers, Daniel
- WARNING: This function fundamentally races against drm_dev_unplug(). It is
- recommended that drivers instead use the underlying drm_dev_enter() and
- WARNING: This function fundamentally races against drm_dev_unregister(). It
*/
- is recommended that drivers instead use the underlying drm_dev_enter() and
- drm_dev_exit() function pairs.
static inline bool drm_dev_is_unplugged(struct drm_device *dev)
2.20.1
Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx
On Mon, Feb 04, 2019 at 06:35:28PM +0100, Noralf Trønnes wrote:
Den 04.02.2019 16.41, skrev Daniel Vetter:
On Sun, Feb 03, 2019 at 04:41:56PM +0100, Noralf Trønnes wrote:
The only thing now that makes drm_dev_unplug() special is that it sets drm_device->unplugged. Move this code to drm_dev_unregister() so that we can remove drm_dev_unplug().
Signed-off-by: Noralf Trønnes noralf@tronnes.org
[...]
drivers/gpu/drm/drm_drv.c | 27 +++++++++++++++------------ include/drm/drm_drv.h | 10 ++++------ 2 files changed, 19 insertions(+), 18 deletions(-)
diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c index 05bbc2b622fc..e0941200edc6 100644 --- a/drivers/gpu/drm/drm_drv.c +++ b/drivers/gpu/drm/drm_drv.c @@ -366,15 +366,6 @@ EXPORT_SYMBOL(drm_dev_exit); */ void drm_dev_unplug(struct drm_device *dev) {
- /*
* After synchronizing any critical read section is guaranteed to see* the new value of ->unplugged, and any critical section which might* still have seen the old value of ->unplugged is guaranteed to have* finished.*/- dev->unplugged = true;
- synchronize_srcu(&drm_unplug_srcu);
- drm_dev_unregister(dev); drm_dev_put(dev);
} @@ -832,11 +823,14 @@ EXPORT_SYMBOL(drm_dev_register);
- drm_dev_register() but does not deallocate the device. The caller must call
- drm_dev_put() to drop their final reference.
- A special form of unregistering for hotpluggable devices is drm_dev_unplug(),
- which can be called while there are still open users of @dev.
- This function can be called while there are still open users of @dev as long
- as the driver protects its device resources using drm_dev_enter() and
- drm_dev_exit().
- This should be called first in the device teardown code to make sure
- userspace can't access the device instance any more.
- userspace can't access the device instance any more. Drivers that support
- device unplug will probably want to call drm_atomic_helper_shutdown() first
Read once more with a bit more coffee, spotted this:
s/first/afterwards/ - shutting down the hw before we've taken it away from userspace is kinda the wrong way round. It should be the inverse of driver load, which is 1) allocate structures 2) prep hw 3) register driver with the world (simplified ofc).
The problem is that drm_dev_unregister() sets the device as unplugged and if drm_atomic_helper_shutdown() is called afterwards it's not allowed to touch hardware.
I know it's the wrong order, but the only way to do it in the right order is to have a separate function that sets unplugged:
drm_dev_unregister(); drm_atomic_helper_shutdown(); drm_dev_set_unplugged();
Annoying ... but yeah calling _shutdown() before we stopped userspace is also not going to work. Because userspace could quickly re-enable something, and then the refcounts would be all wrong again and leaking objects.
I get a bit the feeling we're over-optimizing here with trying to devm-ize drm_dev_register. Just getting drm_device correctly devm-ized is a big step forward already, and will open up a lot of TODO items across a lot of drivers. E.g. we could add a drm_dev_kzalloc, for allocating all the drm_* structs, which gets released together with drm_device. I think that's a much clearer path forward, I think we all agree that getting the kfree out of the driver codes is a good thing, and it would allow us to do this correctly.
Then once we have that and rolled out to a few drivers we can reconsider the entire unregister/shutdown gordian knot here. Atm I just have no idea how to do this properly :-/
Thoughts, other ideas?
Cheers, Daniel
Noralf.
*/
- in order to disable the hardware on regular driver module unload.
void drm_dev_unregister(struct drm_device *dev) { @@ -845,6 +839,15 @@ void drm_dev_unregister(struct drm_device *dev) if (drm_core_check_feature(dev, DRIVER_LEGACY)) drm_lastclose(dev);
/*
* After synchronizing any critical read section is guaranteed to see* the new value of ->unplugged, and any critical section which might* still have seen the old value of ->unplugged is guaranteed to have* finished.*/dev->unplugged = true;
synchronize_srcu(&drm_unplug_srcu);
dev->registered = false;
drm_client_dev_unregister(dev);
diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h index ca46a45a9cce..c50696c82a42 100644 --- a/include/drm/drm_drv.h +++ b/include/drm/drm_drv.h @@ -736,13 +736,11 @@ void drm_dev_unplug(struct drm_device *dev);
- drm_dev_is_unplugged - is a DRM device unplugged
- @dev: DRM device
- This function can be called to check whether a hotpluggable is unplugged.
- Unplugging itself is singalled through drm_dev_unplug(). If a device is
- unplugged, these two functions guarantee that any store before calling
- drm_dev_unplug() is visible to callers of this function after it completes
- This function can be called to check whether @dev is unregistered. This can
- be used to detect that the underlying parent device is gone.
I think it'd be good to keep the first part, and just update the reference to drm_dev_unregister. So:
- This function can be called to check whether a hotpluggable is unplugged.
- Unplugging itself is singalled through drm_dev_unregister(). If a device is
- unplugged, these two functions guarantee that any store before calling
- drm_dev_unregister() is visible to callers of this function after it
- completes.
I think your version shrugs a few important details under the rug. With those nits addressed:
Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch
Cheers, Daniel
- WARNING: This function fundamentally races against drm_dev_unplug(). It is
- recommended that drivers instead use the underlying drm_dev_enter() and
- WARNING: This function fundamentally races against drm_dev_unregister(). It
*/
- is recommended that drivers instead use the underlying drm_dev_enter() and
- drm_dev_exit() function pairs.
static inline bool drm_dev_is_unplugged(struct drm_device *dev)
2.20.1
Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx
Den 05.02.2019 10.11, skrev Daniel Vetter:
On Mon, Feb 04, 2019 at 06:35:28PM +0100, Noralf Trønnes wrote:
Den 04.02.2019 16.41, skrev Daniel Vetter:
On Sun, Feb 03, 2019 at 04:41:56PM +0100, Noralf Trønnes wrote:
The only thing now that makes drm_dev_unplug() special is that it sets drm_device->unplugged. Move this code to drm_dev_unregister() so that we can remove drm_dev_unplug().
Signed-off-by: Noralf Trønnes noralf@tronnes.org
[...]
drivers/gpu/drm/drm_drv.c | 27 +++++++++++++++------------ include/drm/drm_drv.h | 10 ++++------ 2 files changed, 19 insertions(+), 18 deletions(-)
diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c index 05bbc2b622fc..e0941200edc6 100644 --- a/drivers/gpu/drm/drm_drv.c +++ b/drivers/gpu/drm/drm_drv.c @@ -366,15 +366,6 @@ EXPORT_SYMBOL(drm_dev_exit); */ void drm_dev_unplug(struct drm_device *dev) {
- /*
* After synchronizing any critical read section is guaranteed to see* the new value of ->unplugged, and any critical section which might* still have seen the old value of ->unplugged is guaranteed to have* finished.*/- dev->unplugged = true;
- synchronize_srcu(&drm_unplug_srcu);
- drm_dev_unregister(dev); drm_dev_put(dev);
} @@ -832,11 +823,14 @@ EXPORT_SYMBOL(drm_dev_register);
- drm_dev_register() but does not deallocate the device. The caller must call
- drm_dev_put() to drop their final reference.
- A special form of unregistering for hotpluggable devices is drm_dev_unplug(),
- which can be called while there are still open users of @dev.
- This function can be called while there are still open users of @dev as long
- as the driver protects its device resources using drm_dev_enter() and
- drm_dev_exit().
- This should be called first in the device teardown code to make sure
- userspace can't access the device instance any more.
- userspace can't access the device instance any more. Drivers that support
- device unplug will probably want to call drm_atomic_helper_shutdown() first
Read once more with a bit more coffee, spotted this:
s/first/afterwards/ - shutting down the hw before we've taken it away from userspace is kinda the wrong way round. It should be the inverse of driver load, which is 1) allocate structures 2) prep hw 3) register driver with the world (simplified ofc).
The problem is that drm_dev_unregister() sets the device as unplugged and if drm_atomic_helper_shutdown() is called afterwards it's not allowed to touch hardware.
I know it's the wrong order, but the only way to do it in the right order is to have a separate function that sets unplugged:
drm_dev_unregister(); drm_atomic_helper_shutdown(); drm_dev_set_unplugged();
Annoying ... but yeah calling _shutdown() before we stopped userspace is also not going to work. Because userspace could quickly re-enable something, and then the refcounts would be all wrong again and leaking objects.
What happens with a USB device that is unplugged with open userspace, will that leak objects?
I get a bit the feeling we're over-optimizing here with trying to devm-ize drm_dev_register. Just getting drm_device correctly devm-ized is a big step forward already, and will open up a lot of TODO items across a lot of drivers. E.g. we could add a drm_dev_kzalloc, for allocating all the drm_* structs, which gets released together with drm_device. I think that's a much clearer path forward, I think we all agree that getting the kfree out of the driver codes is a good thing, and it would allow us to do this correctly.
Then once we have that and rolled out to a few drivers we can reconsider the entire unregister/shutdown gordian knot here. Atm I just have no idea how to do this properly :-/
Thoughts, other ideas?
Yeah, I've come to the conclusion that devm_drm_dev_register() doesn't make much sense if we need a driver remove callback anyways.
I think devm_drm_dev_init() makes sense because it yields a cleaner probe() function. An additional benefit is that it requires a drm_driver->release function which is a step in the right direction to get the drm_device lifetime right.
Do we agree that a drm_dev_set_unplugged() function is necessary to get the remove/disconnect order right?
What about drm_dev_unplug() maybe I should just leave it be?
- amd uses drm_driver->unload, so that one takes some work to get right to support unplug. It doesn't check the unplugged state, so really doesn't need drm_dev_unplug() I guess. Do they have cards that can be hotplugged? - udl uses drm_driver->unload, doesn't use drm_atomic_helper_shutdown(). It has only one drm_dev_is_unplugged() check and that is in its fbdev->open callback. - xen calls drm_atomic_helper_shutdown() in its drm_driver->release callback which I guess is not correct.
This is what it will look like with a set unplugged function:
void drm_dev_unplug(struct drm_device *dev) { drm_dev_set_unplugged(dev); drm_dev_unregister(dev); drm_dev_put(dev); }
Hm, I should probably remove it to avoid further use of it since it's not correct for a modern driver.
Noralf.
Cheers, Daniel
Noralf.
*/
- in order to disable the hardware on regular driver module unload.
void drm_dev_unregister(struct drm_device *dev) { @@ -845,6 +839,15 @@ void drm_dev_unregister(struct drm_device *dev) if (drm_core_check_feature(dev, DRIVER_LEGACY)) drm_lastclose(dev);
/*
* After synchronizing any critical read section is guaranteed to see* the new value of ->unplugged, and any critical section which might* still have seen the old value of ->unplugged is guaranteed to have* finished.*/dev->unplugged = true;
synchronize_srcu(&drm_unplug_srcu);
dev->registered = false;
drm_client_dev_unregister(dev);
diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h index ca46a45a9cce..c50696c82a42 100644 --- a/include/drm/drm_drv.h +++ b/include/drm/drm_drv.h @@ -736,13 +736,11 @@ void drm_dev_unplug(struct drm_device *dev);
- drm_dev_is_unplugged - is a DRM device unplugged
- @dev: DRM device
- This function can be called to check whether a hotpluggable is unplugged.
- Unplugging itself is singalled through drm_dev_unplug(). If a device is
- unplugged, these two functions guarantee that any store before calling
- drm_dev_unplug() is visible to callers of this function after it completes
- This function can be called to check whether @dev is unregistered. This can
- be used to detect that the underlying parent device is gone.
I think it'd be good to keep the first part, and just update the reference to drm_dev_unregister. So:
- This function can be called to check whether a hotpluggable is unplugged.
- Unplugging itself is singalled through drm_dev_unregister(). If a device is
- unplugged, these two functions guarantee that any store before calling
- drm_dev_unregister() is visible to callers of this function after it
- completes.
I think your version shrugs a few important details under the rug. With those nits addressed:
Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch
Cheers, Daniel
- WARNING: This function fundamentally races against drm_dev_unplug(). It is
- recommended that drivers instead use the underlying drm_dev_enter() and
- WARNING: This function fundamentally races against drm_dev_unregister(). It
*/
- is recommended that drivers instead use the underlying drm_dev_enter() and
- drm_dev_exit() function pairs.
static inline bool drm_dev_is_unplugged(struct drm_device *dev)
2.20.1
Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx
On Tue, Feb 05, 2019 at 11:20:55AM +0100, Noralf Trønnes wrote:
Den 05.02.2019 10.11, skrev Daniel Vetter:
On Mon, Feb 04, 2019 at 06:35:28PM +0100, Noralf Trønnes wrote:
Den 04.02.2019 16.41, skrev Daniel Vetter:
On Sun, Feb 03, 2019 at 04:41:56PM +0100, Noralf Trønnes wrote:
The only thing now that makes drm_dev_unplug() special is that it sets drm_device->unplugged. Move this code to drm_dev_unregister() so that we can remove drm_dev_unplug().
Signed-off-by: Noralf Trønnes noralf@tronnes.org
[...]
drivers/gpu/drm/drm_drv.c | 27 +++++++++++++++------------ include/drm/drm_drv.h | 10 ++++------ 2 files changed, 19 insertions(+), 18 deletions(-)
diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c index 05bbc2b622fc..e0941200edc6 100644 --- a/drivers/gpu/drm/drm_drv.c +++ b/drivers/gpu/drm/drm_drv.c @@ -366,15 +366,6 @@ EXPORT_SYMBOL(drm_dev_exit); */ void drm_dev_unplug(struct drm_device *dev) {
- /*
* After synchronizing any critical read section is guaranteed to see* the new value of ->unplugged, and any critical section which might* still have seen the old value of ->unplugged is guaranteed to have* finished.*/- dev->unplugged = true;
- synchronize_srcu(&drm_unplug_srcu);
- drm_dev_unregister(dev); drm_dev_put(dev);
} @@ -832,11 +823,14 @@ EXPORT_SYMBOL(drm_dev_register);
- drm_dev_register() but does not deallocate the device. The caller must call
- drm_dev_put() to drop their final reference.
- A special form of unregistering for hotpluggable devices is drm_dev_unplug(),
- which can be called while there are still open users of @dev.
- This function can be called while there are still open users of @dev as long
- as the driver protects its device resources using drm_dev_enter() and
- drm_dev_exit().
- This should be called first in the device teardown code to make sure
- userspace can't access the device instance any more.
- userspace can't access the device instance any more. Drivers that support
- device unplug will probably want to call drm_atomic_helper_shutdown() first
Read once more with a bit more coffee, spotted this:
s/first/afterwards/ - shutting down the hw before we've taken it away from userspace is kinda the wrong way round. It should be the inverse of driver load, which is 1) allocate structures 2) prep hw 3) register driver with the world (simplified ofc).
The problem is that drm_dev_unregister() sets the device as unplugged and if drm_atomic_helper_shutdown() is called afterwards it's not allowed to touch hardware.
I know it's the wrong order, but the only way to do it in the right order is to have a separate function that sets unplugged:
drm_dev_unregister(); drm_atomic_helper_shutdown(); drm_dev_set_unplugged();
Annoying ... but yeah calling _shutdown() before we stopped userspace is also not going to work. Because userspace could quickly re-enable something, and then the refcounts would be all wrong again and leaking objects.
What happens with a USB device that is unplugged with open userspace, will that leak objects?
Maybe we've jumped to conclusions. drm_atomic_helper_shutdown() will run as normal, the only thing that should be skipped is actually touching the hw (as long as the driver doesn't protect too much with drm_dev_enter/exit). So all the software updates (including refcounting updates) will still be done. Ofc current udl is not yet atomic, so in reality something else happens.
And we ofc still have the same issue that if you just unload the driver, then the hw will stay on (which might really confuse the driver on next load, when it assumes that it only gets loaded from cold boot where everything is off - which usually is the case on an arm soc at least).
I get a bit the feeling we're over-optimizing here with trying to devm-ize drm_dev_register. Just getting drm_device correctly devm-ized is a big step forward already, and will open up a lot of TODO items across a lot of drivers. E.g. we could add a drm_dev_kzalloc, for allocating all the drm_* structs, which gets released together with drm_device. I think that's a much clearer path forward, I think we all agree that getting the kfree out of the driver codes is a good thing, and it would allow us to do this correctly.
Then once we have that and rolled out to a few drivers we can reconsider the entire unregister/shutdown gordian knot here. Atm I just have no idea how to do this properly :-/
Thoughts, other ideas?
Yeah, I've come to the conclusion that devm_drm_dev_register() doesn't make much sense if we need a driver remove callback anyways.
Yup, that's what I meant with the above: - merge devm_drm_dev_register, use it a lot. This is definitely a good idea. - create a drm_dev_kzalloc, which automatically releases memory on the final drm_dev_put. Use it every in drivers for drm structures, especially in those drivers that currently use devm (which releases those allocations potentialy too early on unplug). - figure out the next steps after that
I think devm_drm_dev_init() makes sense because it yields a cleaner probe() function. An additional benefit is that it requires a drm_driver->release function which is a step in the right direction to get the drm_device lifetime right.
Do we agree that a drm_dev_set_unplugged() function is necessary to get the remove/disconnect order right?
What about drm_dev_unplug() maybe I should just leave it be?
- amd uses drm_driver->unload, so that one takes some work to get right to support unplug. It doesn't check the unplugged state, so really doesn't need drm_dev_unplug() I guess. Do they have cards that can be hotplugged?
Yeah amd still uses ->load and ->unload, which is not great unfortunately. I just stumbled over that when I tried to make a series to disable the global drm_global_mutex for most drivers ...
- udl uses drm_driver->unload, doesn't use drm_atomic_helper_shutdown(). It has only one drm_dev_is_unplugged() check and that is in its fbdev->open callback.
udl isn't atomic, so can't use the atomic helpers. pre-atomic doesn't have refcounting issues when something is left on iirc. I think udl is written under the assumption that ->unload is always called for an unplug, never for an actual unload.
- xen calls drm_atomic_helper_shutdown() in its drm_driver->release callback which I guess is not correct.
Yeah this smells fishy. ->release is supposed to be for cleaning up kernel structures, not for cleaning up the hw. So maybe drm_mode_config_cleanup could be put there, not sure honestly. But definitely not _shutdown().
This is what it will look like with a set unplugged function:
void drm_dev_unplug(struct drm_device *dev) { drm_dev_set_unplugged(dev); drm_dev_unregister(dev); drm_dev_put(dev); }
Hm, I should probably remove it to avoid further use of it since it's not correct for a modern driver.
I think something flew over my head ... what's the drm_dev_set_unplugged for? I think I'm not following you ...
Thanks, Daniel
Noralf.
Cheers, Daniel
Noralf.
*/
- in order to disable the hardware on regular driver module unload.
void drm_dev_unregister(struct drm_device *dev) { @@ -845,6 +839,15 @@ void drm_dev_unregister(struct drm_device *dev) if (drm_core_check_feature(dev, DRIVER_LEGACY)) drm_lastclose(dev);
/*
* After synchronizing any critical read section is guaranteed to see* the new value of ->unplugged, and any critical section which might* still have seen the old value of ->unplugged is guaranteed to have* finished.*/dev->unplugged = true;
synchronize_srcu(&drm_unplug_srcu);
dev->registered = false;
drm_client_dev_unregister(dev);
diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h index ca46a45a9cce..c50696c82a42 100644 --- a/include/drm/drm_drv.h +++ b/include/drm/drm_drv.h @@ -736,13 +736,11 @@ void drm_dev_unplug(struct drm_device *dev);
- drm_dev_is_unplugged - is a DRM device unplugged
- @dev: DRM device
- This function can be called to check whether a hotpluggable is unplugged.
- Unplugging itself is singalled through drm_dev_unplug(). If a device is
- unplugged, these two functions guarantee that any store before calling
- drm_dev_unplug() is visible to callers of this function after it completes
- This function can be called to check whether @dev is unregistered. This can
- be used to detect that the underlying parent device is gone.
I think it'd be good to keep the first part, and just update the reference to drm_dev_unregister. So:
- This function can be called to check whether a hotpluggable is unplugged.
- Unplugging itself is singalled through drm_dev_unregister(). If a device is
- unplugged, these two functions guarantee that any store before calling
- drm_dev_unregister() is visible to callers of this function after it
- completes.
I think your version shrugs a few important details under the rug. With those nits addressed:
Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch
Cheers, Daniel
- WARNING: This function fundamentally races against drm_dev_unplug(). It is
- recommended that drivers instead use the underlying drm_dev_enter() and
- WARNING: This function fundamentally races against drm_dev_unregister(). It
*/
- is recommended that drivers instead use the underlying drm_dev_enter() and
- drm_dev_exit() function pairs.
static inline bool drm_dev_is_unplugged(struct drm_device *dev)
2.20.1
Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx
Den 05.02.2019 17.31, skrev Daniel Vetter:
On Tue, Feb 05, 2019 at 11:20:55AM +0100, Noralf Trønnes wrote:
Den 05.02.2019 10.11, skrev Daniel Vetter:
On Mon, Feb 04, 2019 at 06:35:28PM +0100, Noralf Trønnes wrote:
Den 04.02.2019 16.41, skrev Daniel Vetter:
On Sun, Feb 03, 2019 at 04:41:56PM +0100, Noralf Trønnes wrote:
The only thing now that makes drm_dev_unplug() special is that it sets drm_device->unplugged. Move this code to drm_dev_unregister() so that we can remove drm_dev_unplug().
Signed-off-by: Noralf Trønnes noralf@tronnes.org
[...]
drivers/gpu/drm/drm_drv.c | 27 +++++++++++++++------------ include/drm/drm_drv.h | 10 ++++------ 2 files changed, 19 insertions(+), 18 deletions(-)
diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c index 05bbc2b622fc..e0941200edc6 100644 --- a/drivers/gpu/drm/drm_drv.c +++ b/drivers/gpu/drm/drm_drv.c @@ -366,15 +366,6 @@ EXPORT_SYMBOL(drm_dev_exit); */ void drm_dev_unplug(struct drm_device *dev) {
- /*
* After synchronizing any critical read section is guaranteed to see* the new value of ->unplugged, and any critical section which might* still have seen the old value of ->unplugged is guaranteed to have* finished.*/- dev->unplugged = true;
- synchronize_srcu(&drm_unplug_srcu);
- drm_dev_unregister(dev); drm_dev_put(dev);
} @@ -832,11 +823,14 @@ EXPORT_SYMBOL(drm_dev_register);
- drm_dev_register() but does not deallocate the device. The caller must call
- drm_dev_put() to drop their final reference.
- A special form of unregistering for hotpluggable devices is drm_dev_unplug(),
- which can be called while there are still open users of @dev.
- This function can be called while there are still open users of @dev as long
- as the driver protects its device resources using drm_dev_enter() and
- drm_dev_exit().
- This should be called first in the device teardown code to make sure
- userspace can't access the device instance any more.
- userspace can't access the device instance any more. Drivers that support
- device unplug will probably want to call drm_atomic_helper_shutdown() first
Read once more with a bit more coffee, spotted this:
s/first/afterwards/ - shutting down the hw before we've taken it away from userspace is kinda the wrong way round. It should be the inverse of driver load, which is 1) allocate structures 2) prep hw 3) register driver with the world (simplified ofc).
The problem is that drm_dev_unregister() sets the device as unplugged and if drm_atomic_helper_shutdown() is called afterwards it's not allowed to touch hardware.
I know it's the wrong order, but the only way to do it in the right order is to have a separate function that sets unplugged:
drm_dev_unregister(); drm_atomic_helper_shutdown(); drm_dev_set_unplugged();
Annoying ... but yeah calling _shutdown() before we stopped userspace is also not going to work. Because userspace could quickly re-enable something, and then the refcounts would be all wrong again and leaking objects.
What happens with a USB device that is unplugged with open userspace, will that leak objects?
Maybe we've jumped to conclusions. drm_atomic_helper_shutdown() will run as normal, the only thing that should be skipped is actually touching the hw (as long as the driver doesn't protect too much with drm_dev_enter/exit). So all the software updates (including refcounting updates) will still be done. Ofc current udl is not yet atomic, so in reality something else happens.
And we ofc still have the same issue that if you just unload the driver, then the hw will stay on (which might really confuse the driver on next load, when it assumes that it only gets loaded from cold boot where everything is off - which usually is the case on an arm soc at least).
I get a bit the feeling we're over-optimizing here with trying to devm-ize drm_dev_register. Just getting drm_device correctly devm-ized is a big step forward already, and will open up a lot of TODO items across a lot of drivers. E.g. we could add a drm_dev_kzalloc, for allocating all the drm_* structs, which gets released together with drm_device. I think that's a much clearer path forward, I think we all agree that getting the kfree out of the driver codes is a good thing, and it would allow us to do this correctly.
Then once we have that and rolled out to a few drivers we can reconsider the entire unregister/shutdown gordian knot here. Atm I just have no idea how to do this properly :-/
Thoughts, other ideas?
Yeah, I've come to the conclusion that devm_drm_dev_register() doesn't make much sense if we need a driver remove callback anyways.
Yup, that's what I meant with the above:
- merge devm_drm_dev_register, use it a lot. This is definitely a good idea.
- create a drm_dev_kzalloc, which automatically releases memory on the final drm_dev_put. Use it every in drivers for drm structures, especially in those drivers that currently use devm (which releases those allocations potentialy too early on unplug).
- figure out the next steps after that
I think devm_drm_dev_init() makes sense because it yields a cleaner probe() function. An additional benefit is that it requires a drm_driver->release function which is a step in the right direction to get the drm_device lifetime right.
Do we agree that a drm_dev_set_unplugged() function is necessary to get the remove/disconnect order right?
What about drm_dev_unplug() maybe I should just leave it be?
- amd uses drm_driver->unload, so that one takes some work to get right to support unplug. It doesn't check the unplugged state, so really doesn't need drm_dev_unplug() I guess. Do they have cards that can be hotplugged?
Yeah amd still uses ->load and ->unload, which is not great unfortunately. I just stumbled over that when I tried to make a series to disable the global drm_global_mutex for most drivers ...
- udl uses drm_driver->unload, doesn't use drm_atomic_helper_shutdown(). It has only one drm_dev_is_unplugged() check and that is in its fbdev->open callback.
udl isn't atomic, so can't use the atomic helpers. pre-atomic doesn't have refcounting issues when something is left on iirc. I think udl is written under the assumption that ->unload is always called for an unplug, never for an actual unload.
- xen calls drm_atomic_helper_shutdown() in its drm_driver->release callback which I guess is not correct.
Yeah this smells fishy. ->release is supposed to be for cleaning up kernel structures, not for cleaning up the hw. So maybe drm_mode_config_cleanup could be put there, not sure honestly. But definitely not _shutdown().
This is what it will look like with a set unplugged function:
void drm_dev_unplug(struct drm_device *dev) { drm_dev_set_unplugged(dev); drm_dev_unregister(dev); drm_dev_put(dev); }
Hm, I should probably remove it to avoid further use of it since it's not correct for a modern driver.
I think something flew over my head ... what's the drm_dev_set_unplugged for? I think I'm not following you ...
Taking it a few steps back:
This patch proposes to move 'dev->unplugged = true' from drm_dev_unplug() to drm_dev_unregister().
Additionally I proposed this change to the drm_dev_unregister() docs:
* This should be called first in the device teardown code to make sure - * userspace can't access the device instance any more. + * userspace can't access the device instance any more. Drivers that support + * device unplug will probably want to call drm_atomic_helper_shutdown() first + * in order to disable the hardware on regular driver module unload.
Which would give a driver remove callback like this:
static int driver_remove() { drm_atomic_helper_shutdown(); drm_dev_unregister(); }
Your reaction was that drm_atomic_helper_shutdown() needs to be called after drm_dev_unregister() to avoid a race resulting in leaked objects. However if we call it afterwards, ->unplugged will be true and the driver can't touch hardware.
Then I proposed moving the unplugged state setting to:
void drm_dev_set_unplugged(struct drm_device *dev) { dev->unplugged = true; synchronize_srcu(&drm_unplug_srcu); }
Now it is possible to avoid the race and still touch hardware:
static int driver_remove() { drm_dev_unregister(); drm_atomic_helper_shutdown(); drm_dev_set_unplugged(); }
But now I'm back to the question: Is it the driver or the device that is going away?
If it's the driver we are fine touching hardware, if it's the device it depends on how we access the device resource and whether the subsystem has protection in place to handle access after the device is gone. I think USB can handle and block device access up until the disconnect callback has finished (no point in doing so though, since the normal operation is that the device is gone, not the driver unloading).
Is there a way to determine who's going away without changes to the device core?
Maybe. The driver can only be unregistered if there are no open file handles because a ref is taken on the driver module.
So maybe something along these lines:
int drm_dev_open_count(struct drm_device *dev) { int open_count;
mutex_lock(&drm_global_mutex); open_count = dev->open_count; mutex_unlock(&drm_global_mutex);
return open_count; }
static int driver_remove() { drm_dev_unregister();
open_count = drm_dev_open_count();
/* Open fd's, device is going away, block access */ if (open_count) drm_dev_set_unplugged();
drm_atomic_helper_shutdown();
/* No open fd's, driver is going away */ if (!open_count) drm_dev_set_unplugged(); }
Personally I have 2 use cases: - tinydrm SPI drivers The only hotpluggable SPI controllers I know of are USB which should handle device access while unregistering. SPI devices can be removed, but the controller driver is still in place so it's safe. - A future USB driver (that I hope to work on when all this core stuff is in place). There's no point in touching the hw, so DRM can be set uplugged right away in the disconnect() callback.
This means that I don't need to know who's going away for my use cases.
This turned out to be quite long winding, but the bottom line is that having a separate function to set the unplugged state seems to give a lot of flexibility for various use cases.
I hope I didn't muddy the waters even more :-)
Noralf.
Thanks, Daniel
Noralf.
Cheers, Daniel
Noralf.
*/
- in order to disable the hardware on regular driver module unload.
void drm_dev_unregister(struct drm_device *dev) { @@ -845,6 +839,15 @@ void drm_dev_unregister(struct drm_device *dev) if (drm_core_check_feature(dev, DRIVER_LEGACY)) drm_lastclose(dev);
/*
* After synchronizing any critical read section is guaranteed to see* the new value of ->unplugged, and any critical section which might* still have seen the old value of ->unplugged is guaranteed to have* finished.*/dev->unplugged = true;
synchronize_srcu(&drm_unplug_srcu);
dev->registered = false;
drm_client_dev_unregister(dev);
diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h index ca46a45a9cce..c50696c82a42 100644 --- a/include/drm/drm_drv.h +++ b/include/drm/drm_drv.h @@ -736,13 +736,11 @@ void drm_dev_unplug(struct drm_device *dev);
- drm_dev_is_unplugged - is a DRM device unplugged
- @dev: DRM device
- This function can be called to check whether a hotpluggable is unplugged.
- Unplugging itself is singalled through drm_dev_unplug(). If a device is
- unplugged, these two functions guarantee that any store before calling
- drm_dev_unplug() is visible to callers of this function after it completes
- This function can be called to check whether @dev is unregistered. This can
- be used to detect that the underlying parent device is gone.
I think it'd be good to keep the first part, and just update the reference to drm_dev_unregister. So:
- This function can be called to check whether a hotpluggable is unplugged.
- Unplugging itself is singalled through drm_dev_unregister(). If a device is
- unplugged, these two functions guarantee that any store before calling
- drm_dev_unregister() is visible to callers of this function after it
- completes.
I think your version shrugs a few important details under the rug. With those nits addressed:
Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch
Cheers, Daniel
- WARNING: This function fundamentally races against drm_dev_unplug(). It is
- recommended that drivers instead use the underlying drm_dev_enter() and
- WARNING: This function fundamentally races against drm_dev_unregister(). It
*/
- is recommended that drivers instead use the underlying drm_dev_enter() and
- drm_dev_exit() function pairs.
static inline bool drm_dev_is_unplugged(struct drm_device *dev)
2.20.1
Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx
On Tue, Feb 05, 2019 at 06:57:50PM +0100, Noralf Trønnes wrote:
Den 05.02.2019 17.31, skrev Daniel Vetter:
On Tue, Feb 05, 2019 at 11:20:55AM +0100, Noralf Trønnes wrote:
Den 05.02.2019 10.11, skrev Daniel Vetter:
On Mon, Feb 04, 2019 at 06:35:28PM +0100, Noralf Trønnes wrote:
Den 04.02.2019 16.41, skrev Daniel Vetter:
On Sun, Feb 03, 2019 at 04:41:56PM +0100, Noralf Trønnes wrote: > The only thing now that makes drm_dev_unplug() special is that it sets > drm_device->unplugged. Move this code to drm_dev_unregister() so that we > can remove drm_dev_unplug(). > > Signed-off-by: Noralf Trønnes noralf@tronnes.org > ---
[...]
> drivers/gpu/drm/drm_drv.c | 27 +++++++++++++++------------ > include/drm/drm_drv.h | 10 ++++------ > 2 files changed, 19 insertions(+), 18 deletions(-) > > diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c > index 05bbc2b622fc..e0941200edc6 100644 > --- a/drivers/gpu/drm/drm_drv.c > +++ b/drivers/gpu/drm/drm_drv.c > @@ -366,15 +366,6 @@ EXPORT_SYMBOL(drm_dev_exit); > */ > void drm_dev_unplug(struct drm_device *dev) > { > - /* > - * After synchronizing any critical read section is guaranteed to see > - * the new value of ->unplugged, and any critical section which might > - * still have seen the old value of ->unplugged is guaranteed to have > - * finished. > - */ > - dev->unplugged = true; > - synchronize_srcu(&drm_unplug_srcu); > - > drm_dev_unregister(dev); > drm_dev_put(dev); > } > @@ -832,11 +823,14 @@ EXPORT_SYMBOL(drm_dev_register); > * drm_dev_register() but does not deallocate the device. The caller must call > * drm_dev_put() to drop their final reference. > * > - * A special form of unregistering for hotpluggable devices is drm_dev_unplug(), > - * which can be called while there are still open users of @dev. > + * This function can be called while there are still open users of @dev as long > + * as the driver protects its device resources using drm_dev_enter() and > + * drm_dev_exit(). > * > * This should be called first in the device teardown code to make sure > - * userspace can't access the device instance any more. > + * userspace can't access the device instance any more. Drivers that support > + * device unplug will probably want to call drm_atomic_helper_shutdown() first
Read once more with a bit more coffee, spotted this:
s/first/afterwards/ - shutting down the hw before we've taken it away from userspace is kinda the wrong way round. It should be the inverse of driver load, which is 1) allocate structures 2) prep hw 3) register driver with the world (simplified ofc).
The problem is that drm_dev_unregister() sets the device as unplugged and if drm_atomic_helper_shutdown() is called afterwards it's not allowed to touch hardware.
I know it's the wrong order, but the only way to do it in the right order is to have a separate function that sets unplugged:
drm_dev_unregister(); drm_atomic_helper_shutdown(); drm_dev_set_unplugged();
Annoying ... but yeah calling _shutdown() before we stopped userspace is also not going to work. Because userspace could quickly re-enable something, and then the refcounts would be all wrong again and leaking objects.
What happens with a USB device that is unplugged with open userspace, will that leak objects?
Maybe we've jumped to conclusions. drm_atomic_helper_shutdown() will run as normal, the only thing that should be skipped is actually touching the hw (as long as the driver doesn't protect too much with drm_dev_enter/exit). So all the software updates (including refcounting updates) will still be done. Ofc current udl is not yet atomic, so in reality something else happens.
And we ofc still have the same issue that if you just unload the driver, then the hw will stay on (which might really confuse the driver on next load, when it assumes that it only gets loaded from cold boot where everything is off - which usually is the case on an arm soc at least).
I get a bit the feeling we're over-optimizing here with trying to devm-ize drm_dev_register. Just getting drm_device correctly devm-ized is a big step forward already, and will open up a lot of TODO items across a lot of drivers. E.g. we could add a drm_dev_kzalloc, for allocating all the drm_* structs, which gets released together with drm_device. I think that's a much clearer path forward, I think we all agree that getting the kfree out of the driver codes is a good thing, and it would allow us to do this correctly.
Then once we have that and rolled out to a few drivers we can reconsider the entire unregister/shutdown gordian knot here. Atm I just have no idea how to do this properly :-/
Thoughts, other ideas?
Yeah, I've come to the conclusion that devm_drm_dev_register() doesn't make much sense if we need a driver remove callback anyways.
Yup, that's what I meant with the above:
- merge devm_drm_dev_register, use it a lot. This is definitely a good idea.
- create a drm_dev_kzalloc, which automatically releases memory on the final drm_dev_put. Use it every in drivers for drm structures, especially in those drivers that currently use devm (which releases those allocations potentialy too early on unplug).
- figure out the next steps after that
I think devm_drm_dev_init() makes sense because it yields a cleaner probe() function. An additional benefit is that it requires a drm_driver->release function which is a step in the right direction to get the drm_device lifetime right.
Do we agree that a drm_dev_set_unplugged() function is necessary to get the remove/disconnect order right?
What about drm_dev_unplug() maybe I should just leave it be?
- amd uses drm_driver->unload, so that one takes some work to get right to support unplug. It doesn't check the unplugged state, so really doesn't need drm_dev_unplug() I guess. Do they have cards that can be hotplugged?
Yeah amd still uses ->load and ->unload, which is not great unfortunately. I just stumbled over that when I tried to make a series to disable the global drm_global_mutex for most drivers ...
- udl uses drm_driver->unload, doesn't use drm_atomic_helper_shutdown(). It has only one drm_dev_is_unplugged() check and that is in its fbdev->open callback.
udl isn't atomic, so can't use the atomic helpers. pre-atomic doesn't have refcounting issues when something is left on iirc. I think udl is written under the assumption that ->unload is always called for an unplug, never for an actual unload.
- xen calls drm_atomic_helper_shutdown() in its drm_driver->release callback which I guess is not correct.
Yeah this smells fishy. ->release is supposed to be for cleaning up kernel structures, not for cleaning up the hw. So maybe drm_mode_config_cleanup could be put there, not sure honestly. But definitely not _shutdown().
This is what it will look like with a set unplugged function:
void drm_dev_unplug(struct drm_device *dev) { drm_dev_set_unplugged(dev); drm_dev_unregister(dev); drm_dev_put(dev); }
Hm, I should probably remove it to avoid further use of it since it's not correct for a modern driver.
I think something flew over my head ... what's the drm_dev_set_unplugged for? I think I'm not following you ...
Taking it a few steps back:
This patch proposes to move 'dev->unplugged = true' from drm_dev_unplug() to drm_dev_unregister().
Additionally I proposed this change to the drm_dev_unregister() docs:
- This should be called first in the device teardown code to make sure
- userspace can't access the device instance any more.
- userspace can't access the device instance any more. Drivers that
support
- device unplug will probably want to call
drm_atomic_helper_shutdown() first
- in order to disable the hardware on regular driver module unload.
Which would give a driver remove callback like this:
static int driver_remove() { drm_atomic_helper_shutdown(); drm_dev_unregister(); }
Your reaction was that drm_atomic_helper_shutdown() needs to be called after drm_dev_unregister() to avoid a race resulting in leaked objects. However if we call it afterwards, ->unplugged will be true and the driver can't touch hardware.
Then I proposed moving the unplugged state setting to:
void drm_dev_set_unplugged(struct drm_device *dev) { dev->unplugged = true; synchronize_srcu(&drm_unplug_srcu); }
Now it is possible to avoid the race and still touch hardware:
static int driver_remove() { drm_dev_unregister(); drm_atomic_helper_shutdown(); drm_dev_set_unplugged(); }
But now I'm back to the question: Is it the driver or the device that is going away?
If it's the driver we are fine touching hardware, if it's the device it depends on how we access the device resource and whether the subsystem has protection in place to handle access after the device is gone. I think USB can handle and block device access up until the disconnect callback has finished (no point in doing so though, since the normal operation is that the device is gone, not the driver unloading).
Is there a way to determine who's going away without changes to the device core?
Maybe. The driver can only be unregistered if there are no open file handles because a ref is taken on the driver module.
This isn't true. You can (not many people do, but it's possible) to unbind through sysfs. The module reference only keeps the cpu instructions valid, nothing else.
So maybe something along these lines:
int drm_dev_open_count(struct drm_device *dev) { int open_count;
mutex_lock(&drm_global_mutex); open_count = dev->open_count; mutex_unlock(&drm_global_mutex);
Random style nit: READ_ONCE, no locking needed (the locks don't change anything, except if you have really strange locking rules). Serves double-duty as a huge warning sign that something tricky is happening.
return open_count; }
static int driver_remove() { drm_dev_unregister();
open_count = drm_dev_open_count();
/* Open fd's, device is going away, block access */ if (open_count) drm_dev_set_unplugged();
drm_atomic_helper_shutdown();
/* No open fd's, driver is going away */ if (!open_count) drm_dev_set_unplugged(); }
Personally I have 2 use cases:
- tinydrm SPI drivers The only hotpluggable SPI controllers I know of are USB which should handle device access while unregistering. SPI devices can be removed, but the controller driver is still in place so it's safe.
- A future USB driver (that I hope to work on when all this core stuff is in place). There's no point in touching the hw, so DRM can be set uplugged right away in the disconnect() callback.
This means that I don't need to know who's going away for my use cases.
This turned out to be quite long winding, but the bottom line is that having a separate function to set the unplugged state seems to give a lot of flexibility for various use cases.
I hope I didn't muddy the waters even more :-)
Hm, I think I get your idea. Since I'm still not sure what the best option is I'm leaning towards just leaving stuff as-is. I.e. drivers which want to shut down hw can do the 1. drm_dev_unregister() 2. drm_atomic_helper_shutdown() sequence. Drivers which care about hotunplug more can do just the drm_dev_unplug().
Yes it's messy and unsatisfactory, but in case of serious doubt I like to wait until maybe in the future we have a good idea. Meanwhile leaving a bit of a mess around is better than charging ahead in a possibly totally wrong direction.
There's cases where clue still hasn't hit me, even years later (or anyone else). That's just how it is sometimes.
Zooming out more looking at the big picture I'd say all your work in the past few years has enormously simplified drm for simple drivers already. If we can't resolve this one here right now that just means you "only" made drm 98% simpler instead of maybe 99%. It's still an epic win :-)
Cheers, Daniel
Noralf.
Thanks, Daniel
Noralf.
Cheers, Daniel
Noralf.
> + * in order to disable the hardware on regular driver module unload. > */ > void drm_dev_unregister(struct drm_device *dev) > { > @@ -845,6 +839,15 @@ void drm_dev_unregister(struct drm_device *dev) > if (drm_core_check_feature(dev, DRIVER_LEGACY)) > drm_lastclose(dev); > > + /* > + * After synchronizing any critical read section is guaranteed to see > + * the new value of ->unplugged, and any critical section which might > + * still have seen the old value of ->unplugged is guaranteed to have > + * finished. > + */ > + dev->unplugged = true; > + synchronize_srcu(&drm_unplug_srcu); > + > dev->registered = false; > > drm_client_dev_unregister(dev); > diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h > index ca46a45a9cce..c50696c82a42 100644 > --- a/include/drm/drm_drv.h > +++ b/include/drm/drm_drv.h > @@ -736,13 +736,11 @@ void drm_dev_unplug(struct drm_device *dev); > * drm_dev_is_unplugged - is a DRM device unplugged > * @dev: DRM device > * > - * This function can be called to check whether a hotpluggable is unplugged. > - * Unplugging itself is singalled through drm_dev_unplug(). If a device is > - * unplugged, these two functions guarantee that any store before calling > - * drm_dev_unplug() is visible to callers of this function after it completes > + * This function can be called to check whether @dev is unregistered. This can > + * be used to detect that the underlying parent device is gone.
I think it'd be good to keep the first part, and just update the reference to drm_dev_unregister. So:
- This function can be called to check whether a hotpluggable is unplugged.
- Unplugging itself is singalled through drm_dev_unregister(). If a device is
- unplugged, these two functions guarantee that any store before calling
- drm_dev_unregister() is visible to callers of this function after it
- completes.
I think your version shrugs a few important details under the rug. With those nits addressed:
Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch
Cheers, Daniel
> * > - * WARNING: This function fundamentally races against drm_dev_unplug(). It is > - * recommended that drivers instead use the underlying drm_dev_enter() and > + * WARNING: This function fundamentally races against drm_dev_unregister(). It > + * is recommended that drivers instead use the underlying drm_dev_enter() and > * drm_dev_exit() function pairs. > */ > static inline bool drm_dev_is_unplugged(struct drm_device *dev) > -- > 2.20.1 > > _______________________________________________ > Intel-gfx mailing list > Intel-gfx@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
Den 06.02.2019 16.26, skrev Daniel Vetter:
On Tue, Feb 05, 2019 at 06:57:50PM +0100, Noralf Trønnes wrote:
Den 05.02.2019 17.31, skrev Daniel Vetter:
On Tue, Feb 05, 2019 at 11:20:55AM +0100, Noralf Trønnes wrote:
Den 05.02.2019 10.11, skrev Daniel Vetter:
On Mon, Feb 04, 2019 at 06:35:28PM +0100, Noralf Trønnes wrote:
Den 04.02.2019 16.41, skrev Daniel Vetter: > On Sun, Feb 03, 2019 at 04:41:56PM +0100, Noralf Trønnes wrote: >> The only thing now that makes drm_dev_unplug() special is that it sets >> drm_device->unplugged. Move this code to drm_dev_unregister() so that we >> can remove drm_dev_unplug(). >> >> Signed-off-by: Noralf Trønnes noralf@tronnes.org >> ---
[...]
>> drivers/gpu/drm/drm_drv.c | 27 +++++++++++++++------------ >> include/drm/drm_drv.h | 10 ++++------ >> 2 files changed, 19 insertions(+), 18 deletions(-) >> >> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c >> index 05bbc2b622fc..e0941200edc6 100644 >> --- a/drivers/gpu/drm/drm_drv.c >> +++ b/drivers/gpu/drm/drm_drv.c >> @@ -366,15 +366,6 @@ EXPORT_SYMBOL(drm_dev_exit); >> */ >> void drm_dev_unplug(struct drm_device *dev) >> { >> - /* >> - * After synchronizing any critical read section is guaranteed to see >> - * the new value of ->unplugged, and any critical section which might >> - * still have seen the old value of ->unplugged is guaranteed to have >> - * finished. >> - */ >> - dev->unplugged = true; >> - synchronize_srcu(&drm_unplug_srcu); >> - >> drm_dev_unregister(dev); >> drm_dev_put(dev); >> } >> @@ -832,11 +823,14 @@ EXPORT_SYMBOL(drm_dev_register); >> * drm_dev_register() but does not deallocate the device. The caller must call >> * drm_dev_put() to drop their final reference. >> * >> - * A special form of unregistering for hotpluggable devices is drm_dev_unplug(), >> - * which can be called while there are still open users of @dev. >> + * This function can be called while there are still open users of @dev as long >> + * as the driver protects its device resources using drm_dev_enter() and >> + * drm_dev_exit(). >> * >> * This should be called first in the device teardown code to make sure >> - * userspace can't access the device instance any more. >> + * userspace can't access the device instance any more. Drivers that support >> + * device unplug will probably want to call drm_atomic_helper_shutdown() first > > Read once more with a bit more coffee, spotted this: > > s/first/afterwards/ - shutting down the hw before we've taken it away from > userspace is kinda the wrong way round. It should be the inverse of driver > load, which is 1) allocate structures 2) prep hw 3) register driver with > the world (simplified ofc). >
The problem is that drm_dev_unregister() sets the device as unplugged and if drm_atomic_helper_shutdown() is called afterwards it's not allowed to touch hardware.
I know it's the wrong order, but the only way to do it in the right order is to have a separate function that sets unplugged:
drm_dev_unregister(); drm_atomic_helper_shutdown(); drm_dev_set_unplugged();
Annoying ... but yeah calling _shutdown() before we stopped userspace is also not going to work. Because userspace could quickly re-enable something, and then the refcounts would be all wrong again and leaking objects.
What happens with a USB device that is unplugged with open userspace, will that leak objects?
Maybe we've jumped to conclusions. drm_atomic_helper_shutdown() will run as normal, the only thing that should be skipped is actually touching the hw (as long as the driver doesn't protect too much with drm_dev_enter/exit). So all the software updates (including refcounting updates) will still be done. Ofc current udl is not yet atomic, so in reality something else happens.
And we ofc still have the same issue that if you just unload the driver, then the hw will stay on (which might really confuse the driver on next load, when it assumes that it only gets loaded from cold boot where everything is off - which usually is the case on an arm soc at least).
I get a bit the feeling we're over-optimizing here with trying to devm-ize drm_dev_register. Just getting drm_device correctly devm-ized is a big step forward already, and will open up a lot of TODO items across a lot of drivers. E.g. we could add a drm_dev_kzalloc, for allocating all the drm_* structs, which gets released together with drm_device. I think that's a much clearer path forward, I think we all agree that getting the kfree out of the driver codes is a good thing, and it would allow us to do this correctly.
Then once we have that and rolled out to a few drivers we can reconsider the entire unregister/shutdown gordian knot here. Atm I just have no idea how to do this properly :-/
Thoughts, other ideas?
Yeah, I've come to the conclusion that devm_drm_dev_register() doesn't make much sense if we need a driver remove callback anyways.
Yup, that's what I meant with the above:
- merge devm_drm_dev_register, use it a lot. This is definitely a good idea.
- create a drm_dev_kzalloc, which automatically releases memory on the final drm_dev_put. Use it every in drivers for drm structures, especially in those drivers that currently use devm (which releases those allocations potentialy too early on unplug).
- figure out the next steps after that
I think devm_drm_dev_init() makes sense because it yields a cleaner probe() function. An additional benefit is that it requires a drm_driver->release function which is a step in the right direction to get the drm_device lifetime right.
Do we agree that a drm_dev_set_unplugged() function is necessary to get the remove/disconnect order right?
What about drm_dev_unplug() maybe I should just leave it be?
- amd uses drm_driver->unload, so that one takes some work to get right to support unplug. It doesn't check the unplugged state, so really doesn't need drm_dev_unplug() I guess. Do they have cards that can be hotplugged?
Yeah amd still uses ->load and ->unload, which is not great unfortunately. I just stumbled over that when I tried to make a series to disable the global drm_global_mutex for most drivers ...
- udl uses drm_driver->unload, doesn't use drm_atomic_helper_shutdown(). It has only one drm_dev_is_unplugged() check and that is in its fbdev->open callback.
udl isn't atomic, so can't use the atomic helpers. pre-atomic doesn't have refcounting issues when something is left on iirc. I think udl is written under the assumption that ->unload is always called for an unplug, never for an actual unload.
- xen calls drm_atomic_helper_shutdown() in its drm_driver->release callback which I guess is not correct.
Yeah this smells fishy. ->release is supposed to be for cleaning up kernel structures, not for cleaning up the hw. So maybe drm_mode_config_cleanup could be put there, not sure honestly. But definitely not _shutdown().
This is what it will look like with a set unplugged function:
void drm_dev_unplug(struct drm_device *dev) { drm_dev_set_unplugged(dev); drm_dev_unregister(dev); drm_dev_put(dev); }
Hm, I should probably remove it to avoid further use of it since it's not correct for a modern driver.
I think something flew over my head ... what's the drm_dev_set_unplugged for? I think I'm not following you ...
Taking it a few steps back:
This patch proposes to move 'dev->unplugged = true' from drm_dev_unplug() to drm_dev_unregister().
Additionally I proposed this change to the drm_dev_unregister() docs:
- This should be called first in the device teardown code to make sure
- userspace can't access the device instance any more.
- userspace can't access the device instance any more. Drivers that
support
- device unplug will probably want to call
drm_atomic_helper_shutdown() first
- in order to disable the hardware on regular driver module unload.
Which would give a driver remove callback like this:
static int driver_remove() { drm_atomic_helper_shutdown(); drm_dev_unregister(); }
Your reaction was that drm_atomic_helper_shutdown() needs to be called after drm_dev_unregister() to avoid a race resulting in leaked objects. However if we call it afterwards, ->unplugged will be true and the driver can't touch hardware.
Then I proposed moving the unplugged state setting to:
void drm_dev_set_unplugged(struct drm_device *dev) { dev->unplugged = true; synchronize_srcu(&drm_unplug_srcu); }
Now it is possible to avoid the race and still touch hardware:
static int driver_remove() { drm_dev_unregister(); drm_atomic_helper_shutdown(); drm_dev_set_unplugged(); }
But now I'm back to the question: Is it the driver or the device that is going away?
If it's the driver we are fine touching hardware, if it's the device it depends on how we access the device resource and whether the subsystem has protection in place to handle access after the device is gone. I think USB can handle and block device access up until the disconnect callback has finished (no point in doing so though, since the normal operation is that the device is gone, not the driver unloading).
Is there a way to determine who's going away without changes to the device core?
Maybe. The driver can only be unregistered if there are no open file handles because a ref is taken on the driver module.
This isn't true. You can (not many people do, but it's possible) to unbind through sysfs. The module reference only keeps the cpu instructions valid, nothing else.
So maybe something along these lines:
int drm_dev_open_count(struct drm_device *dev) { int open_count;
mutex_lock(&drm_global_mutex); open_count = dev->open_count; mutex_unlock(&drm_global_mutex);
Random style nit: READ_ONCE, no locking needed (the locks don't change anything, except if you have really strange locking rules). Serves double-duty as a huge warning sign that something tricky is happening.
return open_count; }
static int driver_remove() { drm_dev_unregister();
open_count = drm_dev_open_count();
/* Open fd's, device is going away, block access */ if (open_count) drm_dev_set_unplugged();
drm_atomic_helper_shutdown();
/* No open fd's, driver is going away */ if (!open_count) drm_dev_set_unplugged(); }
Personally I have 2 use cases:
- tinydrm SPI drivers The only hotpluggable SPI controllers I know of are USB which should handle device access while unregistering. SPI devices can be removed, but the controller driver is still in place so it's safe.
- A future USB driver (that I hope to work on when all this core stuff is in place). There's no point in touching the hw, so DRM can be set uplugged right away in the disconnect() callback.
This means that I don't need to know who's going away for my use cases.
This turned out to be quite long winding, but the bottom line is that having a separate function to set the unplugged state seems to give a lot of flexibility for various use cases.
I hope I didn't muddy the waters even more :-)
Hm, I think I get your idea. Since I'm still not sure what the best option is I'm leaning towards just leaving stuff as-is. I.e. drivers which want to shut down hw can do the 1. drm_dev_unregister() 2. drm_atomic_helper_shutdown() sequence. Drivers which care about hotunplug more can do just the drm_dev_unplug().
Yes it's messy and unsatisfactory, but in case of serious doubt I like to wait until maybe in the future we have a good idea. Meanwhile leaving a bit of a mess around is better than charging ahead in a possibly totally wrong direction.
There's cases where clue still hasn't hit me, even years later (or anyone else). That's just how it is sometimes.
Ok, I'll drop this.
This means that I'll drop devm_drm_dev_init() as well since it doesn't play well with drm_dev_unplug() since both will do drm_dev_put(). Not a big deal really, it just means that I need to add one error path in the probe function so I can drm_dev_put() on error.
Are you still ok with the first bug fix patch in this series?
Zooming out more looking at the big picture I'd say all your work in the past few years has enormously simplified drm for simple drivers already. If we can't resolve this one here right now that just means you "only" made drm 98% simpler instead of maybe 99%. It's still an epic win :-)
Thanks, your mentoring and reviews helped turn my rough ideas into something useful :-)
Noralf.
Cheers, Daniel
Noralf.
Thanks, Daniel
Noralf.
Cheers, Daniel
Noralf.
>> + * in order to disable the hardware on regular driver module unload. >> */ >> void drm_dev_unregister(struct drm_device *dev) >> { >> @@ -845,6 +839,15 @@ void drm_dev_unregister(struct drm_device *dev) >> if (drm_core_check_feature(dev, DRIVER_LEGACY)) >> drm_lastclose(dev); >> >> + /* >> + * After synchronizing any critical read section is guaranteed to see >> + * the new value of ->unplugged, and any critical section which might >> + * still have seen the old value of ->unplugged is guaranteed to have >> + * finished. >> + */ >> + dev->unplugged = true; >> + synchronize_srcu(&drm_unplug_srcu); >> + >> dev->registered = false; >> >> drm_client_dev_unregister(dev); >> diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h >> index ca46a45a9cce..c50696c82a42 100644 >> --- a/include/drm/drm_drv.h >> +++ b/include/drm/drm_drv.h >> @@ -736,13 +736,11 @@ void drm_dev_unplug(struct drm_device *dev); >> * drm_dev_is_unplugged - is a DRM device unplugged >> * @dev: DRM device >> * >> - * This function can be called to check whether a hotpluggable is unplugged. >> - * Unplugging itself is singalled through drm_dev_unplug(). If a device is >> - * unplugged, these two functions guarantee that any store before calling >> - * drm_dev_unplug() is visible to callers of this function after it completes >> + * This function can be called to check whether @dev is unregistered. This can >> + * be used to detect that the underlying parent device is gone. > > I think it'd be good to keep the first part, and just update the reference > to drm_dev_unregister. So: > > * This function can be called to check whether a hotpluggable is unplugged. > * Unplugging itself is singalled through drm_dev_unregister(). If a device is > * unplugged, these two functions guarantee that any store before calling > * drm_dev_unregister() is visible to callers of this function after it > * completes. > > I think your version shrugs a few important details under the rug. With > those nits addressed: > > Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch > > Cheers, Daniel > >> * >> - * WARNING: This function fundamentally races against drm_dev_unplug(). It is >> - * recommended that drivers instead use the underlying drm_dev_enter() and >> + * WARNING: This function fundamentally races against drm_dev_unregister(). It >> + * is recommended that drivers instead use the underlying drm_dev_enter() and >> * drm_dev_exit() function pairs. >> */ >> static inline bool drm_dev_is_unplugged(struct drm_device *dev) >> -- >> 2.20.1 >> >> _______________________________________________ >> Intel-gfx mailing list >> Intel-gfx@lists.freedesktop.org >> https://lists.freedesktop.org/mailman/listinfo/intel-gfx >
On Wed, Feb 06, 2019 at 05:46:51PM +0100, Noralf Trønnes wrote:
Den 06.02.2019 16.26, skrev Daniel Vetter:
On Tue, Feb 05, 2019 at 06:57:50PM +0100, Noralf Trønnes wrote:
Den 05.02.2019 17.31, skrev Daniel Vetter:
On Tue, Feb 05, 2019 at 11:20:55AM +0100, Noralf Trønnes wrote:
Den 05.02.2019 10.11, skrev Daniel Vetter:
On Mon, Feb 04, 2019 at 06:35:28PM +0100, Noralf Trønnes wrote: > > > Den 04.02.2019 16.41, skrev Daniel Vetter: >> On Sun, Feb 03, 2019 at 04:41:56PM +0100, Noralf Trønnes wrote: >>> The only thing now that makes drm_dev_unplug() special is that it sets >>> drm_device->unplugged. Move this code to drm_dev_unregister() so that we >>> can remove drm_dev_unplug(). >>> >>> Signed-off-by: Noralf Trønnes noralf@tronnes.org >>> --- > > [...] > >>> drivers/gpu/drm/drm_drv.c | 27 +++++++++++++++------------ >>> include/drm/drm_drv.h | 10 ++++------ >>> 2 files changed, 19 insertions(+), 18 deletions(-) >>> >>> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c >>> index 05bbc2b622fc..e0941200edc6 100644 >>> --- a/drivers/gpu/drm/drm_drv.c >>> +++ b/drivers/gpu/drm/drm_drv.c >>> @@ -366,15 +366,6 @@ EXPORT_SYMBOL(drm_dev_exit); >>> */ >>> void drm_dev_unplug(struct drm_device *dev) >>> { >>> - /* >>> - * After synchronizing any critical read section is guaranteed to see >>> - * the new value of ->unplugged, and any critical section which might >>> - * still have seen the old value of ->unplugged is guaranteed to have >>> - * finished. >>> - */ >>> - dev->unplugged = true; >>> - synchronize_srcu(&drm_unplug_srcu); >>> - >>> drm_dev_unregister(dev); >>> drm_dev_put(dev); >>> } >>> @@ -832,11 +823,14 @@ EXPORT_SYMBOL(drm_dev_register); >>> * drm_dev_register() but does not deallocate the device. The caller must call >>> * drm_dev_put() to drop their final reference. >>> * >>> - * A special form of unregistering for hotpluggable devices is drm_dev_unplug(), >>> - * which can be called while there are still open users of @dev. >>> + * This function can be called while there are still open users of @dev as long >>> + * as the driver protects its device resources using drm_dev_enter() and >>> + * drm_dev_exit(). >>> * >>> * This should be called first in the device teardown code to make sure >>> - * userspace can't access the device instance any more. >>> + * userspace can't access the device instance any more. Drivers that support >>> + * device unplug will probably want to call drm_atomic_helper_shutdown() first >> >> Read once more with a bit more coffee, spotted this: >> >> s/first/afterwards/ - shutting down the hw before we've taken it away from >> userspace is kinda the wrong way round. It should be the inverse of driver >> load, which is 1) allocate structures 2) prep hw 3) register driver with >> the world (simplified ofc). >> > > The problem is that drm_dev_unregister() sets the device as unplugged > and if drm_atomic_helper_shutdown() is called afterwards it's not > allowed to touch hardware. > > I know it's the wrong order, but the only way to do it in the right > order is to have a separate function that sets unplugged: > > drm_dev_unregister(); > drm_atomic_helper_shutdown(); > drm_dev_set_unplugged();
Annoying ... but yeah calling _shutdown() before we stopped userspace is also not going to work. Because userspace could quickly re-enable something, and then the refcounts would be all wrong again and leaking objects.
What happens with a USB device that is unplugged with open userspace, will that leak objects?
Maybe we've jumped to conclusions. drm_atomic_helper_shutdown() will run as normal, the only thing that should be skipped is actually touching the hw (as long as the driver doesn't protect too much with drm_dev_enter/exit). So all the software updates (including refcounting updates) will still be done. Ofc current udl is not yet atomic, so in reality something else happens.
And we ofc still have the same issue that if you just unload the driver, then the hw will stay on (which might really confuse the driver on next load, when it assumes that it only gets loaded from cold boot where everything is off - which usually is the case on an arm soc at least).
I get a bit the feeling we're over-optimizing here with trying to devm-ize drm_dev_register. Just getting drm_device correctly devm-ized is a big step forward already, and will open up a lot of TODO items across a lot of drivers. E.g. we could add a drm_dev_kzalloc, for allocating all the drm_* structs, which gets released together with drm_device. I think that's a much clearer path forward, I think we all agree that getting the kfree out of the driver codes is a good thing, and it would allow us to do this correctly.
Then once we have that and rolled out to a few drivers we can reconsider the entire unregister/shutdown gordian knot here. Atm I just have no idea how to do this properly :-/
Thoughts, other ideas?
Yeah, I've come to the conclusion that devm_drm_dev_register() doesn't make much sense if we need a driver remove callback anyways.
Yup, that's what I meant with the above:
- merge devm_drm_dev_register, use it a lot. This is definitely a good idea.
- create a drm_dev_kzalloc, which automatically releases memory on the final drm_dev_put. Use it every in drivers for drm structures, especially in those drivers that currently use devm (which releases those allocations potentialy too early on unplug).
- figure out the next steps after that
I think devm_drm_dev_init() makes sense because it yields a cleaner probe() function. An additional benefit is that it requires a drm_driver->release function which is a step in the right direction to get the drm_device lifetime right.
Do we agree that a drm_dev_set_unplugged() function is necessary to get the remove/disconnect order right?
What about drm_dev_unplug() maybe I should just leave it be?
- amd uses drm_driver->unload, so that one takes some work to get right to support unplug. It doesn't check the unplugged state, so really doesn't need drm_dev_unplug() I guess. Do they have cards that can be hotplugged?
Yeah amd still uses ->load and ->unload, which is not great unfortunately. I just stumbled over that when I tried to make a series to disable the global drm_global_mutex for most drivers ...
- udl uses drm_driver->unload, doesn't use drm_atomic_helper_shutdown(). It has only one drm_dev_is_unplugged() check and that is in its fbdev->open callback.
udl isn't atomic, so can't use the atomic helpers. pre-atomic doesn't have refcounting issues when something is left on iirc. I think udl is written under the assumption that ->unload is always called for an unplug, never for an actual unload.
- xen calls drm_atomic_helper_shutdown() in its drm_driver->release callback which I guess is not correct.
Yeah this smells fishy. ->release is supposed to be for cleaning up kernel structures, not for cleaning up the hw. So maybe drm_mode_config_cleanup could be put there, not sure honestly. But definitely not _shutdown().
This is what it will look like with a set unplugged function:
void drm_dev_unplug(struct drm_device *dev) { drm_dev_set_unplugged(dev); drm_dev_unregister(dev); drm_dev_put(dev); }
Hm, I should probably remove it to avoid further use of it since it's not correct for a modern driver.
I think something flew over my head ... what's the drm_dev_set_unplugged for? I think I'm not following you ...
Taking it a few steps back:
This patch proposes to move 'dev->unplugged = true' from drm_dev_unplug() to drm_dev_unregister().
Additionally I proposed this change to the drm_dev_unregister() docs:
- This should be called first in the device teardown code to make sure
- userspace can't access the device instance any more.
- userspace can't access the device instance any more. Drivers that
support
- device unplug will probably want to call
drm_atomic_helper_shutdown() first
- in order to disable the hardware on regular driver module unload.
Which would give a driver remove callback like this:
static int driver_remove() { drm_atomic_helper_shutdown(); drm_dev_unregister(); }
Your reaction was that drm_atomic_helper_shutdown() needs to be called after drm_dev_unregister() to avoid a race resulting in leaked objects. However if we call it afterwards, ->unplugged will be true and the driver can't touch hardware.
Then I proposed moving the unplugged state setting to:
void drm_dev_set_unplugged(struct drm_device *dev) { dev->unplugged = true; synchronize_srcu(&drm_unplug_srcu); }
Now it is possible to avoid the race and still touch hardware:
static int driver_remove() { drm_dev_unregister(); drm_atomic_helper_shutdown(); drm_dev_set_unplugged(); }
But now I'm back to the question: Is it the driver or the device that is going away?
If it's the driver we are fine touching hardware, if it's the device it depends on how we access the device resource and whether the subsystem has protection in place to handle access after the device is gone. I think USB can handle and block device access up until the disconnect callback has finished (no point in doing so though, since the normal operation is that the device is gone, not the driver unloading).
Is there a way to determine who's going away without changes to the device core?
Maybe. The driver can only be unregistered if there are no open file handles because a ref is taken on the driver module.
This isn't true. You can (not many people do, but it's possible) to unbind through sysfs. The module reference only keeps the cpu instructions valid, nothing else.
So maybe something along these lines:
int drm_dev_open_count(struct drm_device *dev) { int open_count;
mutex_lock(&drm_global_mutex); open_count = dev->open_count; mutex_unlock(&drm_global_mutex);
Random style nit: READ_ONCE, no locking needed (the locks don't change anything, except if you have really strange locking rules). Serves double-duty as a huge warning sign that something tricky is happening.
return open_count; }
static int driver_remove() { drm_dev_unregister();
open_count = drm_dev_open_count();
/* Open fd's, device is going away, block access */ if (open_count) drm_dev_set_unplugged();
drm_atomic_helper_shutdown();
/* No open fd's, driver is going away */ if (!open_count) drm_dev_set_unplugged(); }
Personally I have 2 use cases:
- tinydrm SPI drivers The only hotpluggable SPI controllers I know of are USB which should handle device access while unregistering. SPI devices can be removed, but the controller driver is still in place so it's safe.
- A future USB driver (that I hope to work on when all this core stuff is in place). There's no point in touching the hw, so DRM can be set uplugged right away in the disconnect() callback.
This means that I don't need to know who's going away for my use cases.
This turned out to be quite long winding, but the bottom line is that having a separate function to set the unplugged state seems to give a lot of flexibility for various use cases.
I hope I didn't muddy the waters even more :-)
Hm, I think I get your idea. Since I'm still not sure what the best option is I'm leaning towards just leaving stuff as-is. I.e. drivers which want to shut down hw can do the 1. drm_dev_unregister() 2. drm_atomic_helper_shutdown() sequence. Drivers which care about hotunplug more can do just the drm_dev_unplug().
Yes it's messy and unsatisfactory, but in case of serious doubt I like to wait until maybe in the future we have a good idea. Meanwhile leaving a bit of a mess around is better than charging ahead in a possibly totally wrong direction.
There's cases where clue still hasn't hit me, even years later (or anyone else). That's just how it is sometimes.
Ok, I'll drop this.
This means that I'll drop devm_drm_dev_init() as well since it doesn't play well with drm_dev_unplug() since both will do drm_dev_put(). Not a big deal really, it just means that I need to add one error path in the probe function so I can drm_dev_put() on error.
Hm, I think we could just move the drm_dev_put out from drm_dev_unplug. And then encourage everyone to use devm_drm_dev_init() everywhere. I do like to get started with auto-cleaned up in drm somehow, and devm_drm_dev_init doing the drm_dev_put() looks like a really good idea.
Are you still ok with the first bug fix patch in this series?
Yeah that one still looks good.
Cheers, Daniel
Zooming out more looking at the big picture I'd say all your work in the past few years has enormously simplified drm for simple drivers already. If we can't resolve this one here right now that just means you "only" made drm 98% simpler instead of maybe 99%. It's still an epic win :-)
Thanks, your mentoring and reviews helped turn my rough ideas into something useful :-)
Noralf.
Cheers, Daniel
Noralf.
Thanks, Daniel
Noralf.
Cheers, Daniel
> Noralf. > >>> + * in order to disable the hardware on regular driver module unload. >>> */ >>> void drm_dev_unregister(struct drm_device *dev) >>> { >>> @@ -845,6 +839,15 @@ void drm_dev_unregister(struct drm_device *dev) >>> if (drm_core_check_feature(dev, DRIVER_LEGACY)) >>> drm_lastclose(dev); >>> >>> + /* >>> + * After synchronizing any critical read section is guaranteed to see >>> + * the new value of ->unplugged, and any critical section which might >>> + * still have seen the old value of ->unplugged is guaranteed to have >>> + * finished. >>> + */ >>> + dev->unplugged = true; >>> + synchronize_srcu(&drm_unplug_srcu); >>> + >>> dev->registered = false; >>> >>> drm_client_dev_unregister(dev); >>> diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h >>> index ca46a45a9cce..c50696c82a42 100644 >>> --- a/include/drm/drm_drv.h >>> +++ b/include/drm/drm_drv.h >>> @@ -736,13 +736,11 @@ void drm_dev_unplug(struct drm_device *dev); >>> * drm_dev_is_unplugged - is a DRM device unplugged >>> * @dev: DRM device >>> * >>> - * This function can be called to check whether a hotpluggable is unplugged. >>> - * Unplugging itself is singalled through drm_dev_unplug(). If a device is >>> - * unplugged, these two functions guarantee that any store before calling >>> - * drm_dev_unplug() is visible to callers of this function after it completes >>> + * This function can be called to check whether @dev is unregistered. This can >>> + * be used to detect that the underlying parent device is gone. >> >> I think it'd be good to keep the first part, and just update the reference >> to drm_dev_unregister. So: >> >> * This function can be called to check whether a hotpluggable is unplugged. >> * Unplugging itself is singalled through drm_dev_unregister(). If a device is >> * unplugged, these two functions guarantee that any store before calling >> * drm_dev_unregister() is visible to callers of this function after it >> * completes. >> >> I think your version shrugs a few important details under the rug. With >> those nits addressed: >> >> Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch >> >> Cheers, Daniel >> >>> * >>> - * WARNING: This function fundamentally races against drm_dev_unplug(). It is >>> - * recommended that drivers instead use the underlying drm_dev_enter() and >>> + * WARNING: This function fundamentally races against drm_dev_unregister(). It >>> + * is recommended that drivers instead use the underlying drm_dev_enter() and >>> * drm_dev_exit() function pairs. >>> */ >>> static inline bool drm_dev_is_unplugged(struct drm_device *dev) >>> -- >>> 2.20.1 >>> >>> _______________________________________________ >>> Intel-gfx mailing list >>> Intel-gfx@lists.freedesktop.org >>> https://lists.freedesktop.org/mailman/listinfo/intel-gfx >>
Daniel Vetter daniel@ffwll.ch writes:
Zooming out more looking at the big picture I'd say all your work in the past few years has enormously simplified drm for simple drivers already. If we can't resolve this one here right now that just means you "only" made drm 98% simpler instead of maybe 99%. It's still an epic win :-)
I'd like to second this. So many of Noralf's cleanups I think "oof, that's a lot of work for a little cleanup here". But we've benefited immensely from it accumulating over the years. Thanks again!
On Sun, Feb 03, 2019 at 04:41:56PM +0100, Noralf Trønnes wrote:
The only thing now that makes drm_dev_unplug() special is that it sets drm_device->unplugged. Move this code to drm_dev_unregister() so that we can remove drm_dev_unplug().
Signed-off-by: Noralf Trønnes noralf@tronnes.org
Maybe s/unplugged/unregistered/ ?
I looked at drm_device->registered, but using that would mean that drm_dev_is_unplugged() would return before drm_device is registered. And given that its current purpose is to prevent race against connector registration, I stayed away from it.
Makes sense. I think having unregistered along with registered might cause some confusion unless it's really clearly documented. Perhaps s/unplugged/unregistered/ and s/registered/initialized/ but init has its own meaning...
I'd hate to hold up the patchset over naming bikeshed, so maybe this would be better off as a follow-on series where everyone can pile on opinions. So,
Reviewed-by: Sean Paul sean@poorly.run
Noralf.
drivers/gpu/drm/drm_drv.c | 27 +++++++++++++++------------ include/drm/drm_drv.h | 10 ++++------ 2 files changed, 19 insertions(+), 18 deletions(-)
diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c index 05bbc2b622fc..e0941200edc6 100644 --- a/drivers/gpu/drm/drm_drv.c +++ b/drivers/gpu/drm/drm_drv.c @@ -366,15 +366,6 @@ EXPORT_SYMBOL(drm_dev_exit); */ void drm_dev_unplug(struct drm_device *dev) {
- /*
* After synchronizing any critical read section is guaranteed to see* the new value of ->unplugged, and any critical section which might* still have seen the old value of ->unplugged is guaranteed to have* finished.*/- dev->unplugged = true;
- synchronize_srcu(&drm_unplug_srcu);
- drm_dev_unregister(dev); drm_dev_put(dev);
} @@ -832,11 +823,14 @@ EXPORT_SYMBOL(drm_dev_register);
- drm_dev_register() but does not deallocate the device. The caller must call
- drm_dev_put() to drop their final reference.
- A special form of unregistering for hotpluggable devices is drm_dev_unplug(),
- which can be called while there are still open users of @dev.
- This function can be called while there are still open users of @dev as long
- as the driver protects its device resources using drm_dev_enter() and
- drm_dev_exit().
- This should be called first in the device teardown code to make sure
- userspace can't access the device instance any more.
- userspace can't access the device instance any more. Drivers that support
- device unplug will probably want to call drm_atomic_helper_shutdown() first
*/
- in order to disable the hardware on regular driver module unload.
void drm_dev_unregister(struct drm_device *dev) { @@ -845,6 +839,15 @@ void drm_dev_unregister(struct drm_device *dev) if (drm_core_check_feature(dev, DRIVER_LEGACY)) drm_lastclose(dev);
/*
* After synchronizing any critical read section is guaranteed to see* the new value of ->unplugged, and any critical section which might* still have seen the old value of ->unplugged is guaranteed to have* finished.*/dev->unplugged = true;
synchronize_srcu(&drm_unplug_srcu);
dev->registered = false;
drm_client_dev_unregister(dev);
diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h index ca46a45a9cce..c50696c82a42 100644 --- a/include/drm/drm_drv.h +++ b/include/drm/drm_drv.h @@ -736,13 +736,11 @@ void drm_dev_unplug(struct drm_device *dev);
- drm_dev_is_unplugged - is a DRM device unplugged
- @dev: DRM device
- This function can be called to check whether a hotpluggable is unplugged.
- Unplugging itself is singalled through drm_dev_unplug(). If a device is
- unplugged, these two functions guarantee that any store before calling
- drm_dev_unplug() is visible to callers of this function after it completes
- This function can be called to check whether @dev is unregistered. This can
- be used to detect that the underlying parent device is gone.
- WARNING: This function fundamentally races against drm_dev_unplug(). It is
- recommended that drivers instead use the underlying drm_dev_enter() and
- WARNING: This function fundamentally races against drm_dev_unregister(). It
*/
- is recommended that drivers instead use the underlying drm_dev_enter() and
- drm_dev_exit() function pairs.
static inline bool drm_dev_is_unplugged(struct drm_device *dev)
2.20.1
On Thu, Feb 07, 2019 at 04:07:33PM -0500, Sean Paul wrote:
On Sun, Feb 03, 2019 at 04:41:56PM +0100, Noralf Trønnes wrote:
The only thing now that makes drm_dev_unplug() special is that it sets drm_device->unplugged. Move this code to drm_dev_unregister() so that we can remove drm_dev_unplug().
Signed-off-by: Noralf Trønnes noralf@tronnes.org
Maybe s/unplugged/unregistered/ ?
I looked at drm_device->registered, but using that would mean that drm_dev_is_unplugged() would return before drm_device is registered. And given that its current purpose is to prevent race against connector registration, I stayed away from it.
Makes sense. I think having unregistered along with registered might cause some confusion unless it's really clearly documented. Perhaps s/unplugged/unregistered/ and s/registered/initialized/ but init has its own meaning...
I'd hate to hold up the patchset over naming bikeshed, so maybe this would be better off as a follow-on series where everyone can pile on opinions. So,
Reviewed-by: Sean Paul sean@poorly.run
Looks like I was dropped from Cc, so I didn't see the replies after Oleksandr's review. So go ahead and disregard this :-)
Sean
Noralf.
drivers/gpu/drm/drm_drv.c | 27 +++++++++++++++------------ include/drm/drm_drv.h | 10 ++++------ 2 files changed, 19 insertions(+), 18 deletions(-)
diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c index 05bbc2b622fc..e0941200edc6 100644 --- a/drivers/gpu/drm/drm_drv.c +++ b/drivers/gpu/drm/drm_drv.c @@ -366,15 +366,6 @@ EXPORT_SYMBOL(drm_dev_exit); */ void drm_dev_unplug(struct drm_device *dev) {
- /*
* After synchronizing any critical read section is guaranteed to see* the new value of ->unplugged, and any critical section which might* still have seen the old value of ->unplugged is guaranteed to have* finished.*/- dev->unplugged = true;
- synchronize_srcu(&drm_unplug_srcu);
- drm_dev_unregister(dev); drm_dev_put(dev);
} @@ -832,11 +823,14 @@ EXPORT_SYMBOL(drm_dev_register);
- drm_dev_register() but does not deallocate the device. The caller must call
- drm_dev_put() to drop their final reference.
- A special form of unregistering for hotpluggable devices is drm_dev_unplug(),
- which can be called while there are still open users of @dev.
- This function can be called while there are still open users of @dev as long
- as the driver protects its device resources using drm_dev_enter() and
- drm_dev_exit().
- This should be called first in the device teardown code to make sure
- userspace can't access the device instance any more.
- userspace can't access the device instance any more. Drivers that support
- device unplug will probably want to call drm_atomic_helper_shutdown() first
*/
- in order to disable the hardware on regular driver module unload.
void drm_dev_unregister(struct drm_device *dev) { @@ -845,6 +839,15 @@ void drm_dev_unregister(struct drm_device *dev) if (drm_core_check_feature(dev, DRIVER_LEGACY)) drm_lastclose(dev);
/*
* After synchronizing any critical read section is guaranteed to see* the new value of ->unplugged, and any critical section which might* still have seen the old value of ->unplugged is guaranteed to have* finished.*/dev->unplugged = true;
synchronize_srcu(&drm_unplug_srcu);
dev->registered = false;
drm_client_dev_unregister(dev);
diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h index ca46a45a9cce..c50696c82a42 100644 --- a/include/drm/drm_drv.h +++ b/include/drm/drm_drv.h @@ -736,13 +736,11 @@ void drm_dev_unplug(struct drm_device *dev);
- drm_dev_is_unplugged - is a DRM device unplugged
- @dev: DRM device
- This function can be called to check whether a hotpluggable is unplugged.
- Unplugging itself is singalled through drm_dev_unplug(). If a device is
- unplugged, these two functions guarantee that any store before calling
- drm_dev_unplug() is visible to callers of this function after it completes
- This function can be called to check whether @dev is unregistered. This can
- be used to detect that the underlying parent device is gone.
- WARNING: This function fundamentally races against drm_dev_unplug(). It is
- recommended that drivers instead use the underlying drm_dev_enter() and
- WARNING: This function fundamentally races against drm_dev_unregister(). It
*/
- is recommended that drivers instead use the underlying drm_dev_enter() and
- drm_dev_exit() function pairs.
static inline bool drm_dev_is_unplugged(struct drm_device *dev)
2.20.1
-- Sean Paul, Software Engineer, Google / Chromium OS
drm_dev_unplug() has been stripped down and is going away. Open code its 2 remaining function calls.
Cc: Alex Deucher alexander.deucher@amd.com Cc: Christian König christian.koenig@amd.com Cc: David (ChunMing) Zhou David1.Zhou@amd.com Signed-off-by: Noralf Trønnes noralf@tronnes.org --- drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c index a1bb3773087b..1265fc07120a 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c @@ -970,7 +970,8 @@ amdgpu_pci_remove(struct pci_dev *pdev) struct drm_device *dev = pci_get_drvdata(pdev);
DRM_ERROR("Device removal is currently not supported outside of fbcon\n"); - drm_dev_unplug(dev); + drm_dev_unregister(dev); + drm_dev_put(dev); pci_disable_device(pdev); pci_set_drvdata(pdev, NULL); }
drm_dev_unplug() has been stripped down and is going away. Open code its 2 remaining function calls.
Cc: Dave Airlie airlied@redhat.com Cc: Sean Paul sean@poorly.run Signed-off-by: Noralf Trønnes noralf@tronnes.org --- drivers/gpu/drm/udl/udl_drv.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/udl/udl_drv.c b/drivers/gpu/drm/udl/udl_drv.c index 22cd2d13e272..063e8e1e2641 100644 --- a/drivers/gpu/drm/udl/udl_drv.c +++ b/drivers/gpu/drm/udl/udl_drv.c @@ -106,7 +106,8 @@ static void udl_usb_disconnect(struct usb_interface *interface) drm_kms_helper_poll_disable(dev); udl_fbdev_unplug(dev); udl_drop_usb(dev); - drm_dev_unplug(dev); + drm_dev_unregister(dev); + drm_dev_put(dev); }
/*
On Sun, Feb 03, 2019 at 04:41:58PM +0100, Noralf Trønnes wrote:
drm_dev_unplug() has been stripped down and is going away. Open code its 2 remaining function calls.
Cc: Dave Airlie airlied@redhat.com Cc: Sean Paul sean@poorly.run
Reviewed-by: Sean Paul sean@poorly.run
Signed-off-by: Noralf Trønnes noralf@tronnes.org
drivers/gpu/drm/udl/udl_drv.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/udl/udl_drv.c b/drivers/gpu/drm/udl/udl_drv.c index 22cd2d13e272..063e8e1e2641 100644 --- a/drivers/gpu/drm/udl/udl_drv.c +++ b/drivers/gpu/drm/udl/udl_drv.c @@ -106,7 +106,8 @@ static void udl_usb_disconnect(struct usb_interface *interface) drm_kms_helper_poll_disable(dev); udl_fbdev_unplug(dev); udl_drop_usb(dev);
- drm_dev_unplug(dev);
- drm_dev_unregister(dev);
- drm_dev_put(dev);
}
/*
2.20.1
drm_dev_unplug() has been stripped down and is going away. Open code its 2 remaining function calls.
Also remove the drm_dev_is_unplugged() check since this can't be true before drm_dev_unregister() is called which happens after the check.
Cc: Oleksandr Andrushchenko oleksandr_andrushchenko@epam.com Signed-off-by: Noralf Trønnes noralf@tronnes.org --- drivers/gpu/drm/xen/xen_drm_front.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/xen/xen_drm_front.c b/drivers/gpu/drm/xen/xen_drm_front.c index 3e78a832d7f9..5c5eb24c6342 100644 --- a/drivers/gpu/drm/xen/xen_drm_front.c +++ b/drivers/gpu/drm/xen/xen_drm_front.c @@ -576,12 +576,9 @@ static void xen_drm_drv_fini(struct xen_drm_front_info *front_info) if (!dev) return;
- /* Nothing to do if device is already unplugged */ - if (drm_dev_is_unplugged(dev)) - return; - drm_kms_helper_poll_fini(dev); - drm_dev_unplug(dev); + drm_dev_unregister(dev); + drm_dev_put(dev);
front_info->drm_info = NULL;
On 2/3/19 5:41 PM, Noralf Trønnes wrote:
drm_dev_unplug() has been stripped down and is going away. Open code its 2 remaining function calls.
Also remove the drm_dev_is_unplugged() check since this can't be true before drm_dev_unregister() is called which happens after the check.
Cc: Oleksandr Andrushchenko oleksandr_andrushchenko@epam.com Signed-off-by: Noralf Trønnes noralf@tronnes.org
drivers/gpu/drm/xen/xen_drm_front.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/xen/xen_drm_front.c b/drivers/gpu/drm/xen/xen_drm_front.c index 3e78a832d7f9..5c5eb24c6342 100644 --- a/drivers/gpu/drm/xen/xen_drm_front.c +++ b/drivers/gpu/drm/xen/xen_drm_front.c @@ -576,12 +576,9 @@ static void xen_drm_drv_fini(struct xen_drm_front_info *front_info) if (!dev) return;
- /* Nothing to do if device is already unplugged */
- if (drm_dev_is_unplugged(dev))
return;
xen_drm_drv_fini is called when the backend changes its state [1], so I just use the check above to prevent possible race conditions here, e.g. do not allow to run unregister code if it is already in progress So, I think we should keep this and probably just add a comment why it is here
- drm_kms_helper_poll_fini(dev);
- drm_dev_unplug(dev);
drm_dev_unregister(dev);
drm_dev_put(dev);
front_info->drm_info = NULL;
[1] https://elixir.bootlin.com/linux/v5.0-rc5/ident/displback_disconnect
Den 04.02.2019 11.42, skrev Oleksandr Andrushchenko:
On 2/3/19 5:41 PM, Noralf Trønnes wrote:
drm_dev_unplug() has been stripped down and is going away. Open code its 2 remaining function calls.
Also remove the drm_dev_is_unplugged() check since this can't be true before drm_dev_unregister() is called which happens after the check.
Cc: Oleksandr Andrushchenko oleksandr_andrushchenko@epam.com Signed-off-by: Noralf Trønnes noralf@tronnes.org
drivers/gpu/drm/xen/xen_drm_front.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/xen/xen_drm_front.c b/drivers/gpu/drm/xen/xen_drm_front.c index 3e78a832d7f9..5c5eb24c6342 100644 --- a/drivers/gpu/drm/xen/xen_drm_front.c +++ b/drivers/gpu/drm/xen/xen_drm_front.c @@ -576,12 +576,9 @@ static void xen_drm_drv_fini(struct xen_drm_front_info *front_info) if (!dev) return;
- /* Nothing to do if device is already unplugged */
- if (drm_dev_is_unplugged(dev))
return;xen_drm_drv_fini is called when the backend changes its state [1], so I just use the check above to prevent possible race conditions here, e.g. do not allow to run unregister code if it is already in progress So, I think we should keep this and probably just add a comment why it is here
Ok, it's just me not reading the code closely enough. I'll put it back in the next version.
Noralf.
- drm_kms_helper_poll_fini(dev);
- drm_dev_unplug(dev);
drm_dev_unregister(dev);
drm_dev_put(dev);
front_info->drm_info = NULL;
[1] https://elixir.bootlin.com/linux/v5.0-rc5/ident/displback_disconnect
There are no users left.
Signed-off-by: Noralf Trønnes noralf@tronnes.org --- drivers/gpu/drm/drm_drv.c | 17 ----------------- include/drm/drm_drv.h | 1 - 2 files changed, 18 deletions(-)
diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c index e0941200edc6..87210d4a9e53 100644 --- a/drivers/gpu/drm/drm_drv.c +++ b/drivers/gpu/drm/drm_drv.c @@ -354,23 +354,6 @@ void drm_dev_exit(int idx) } EXPORT_SYMBOL(drm_dev_exit);
-/** - * drm_dev_unplug - unplug a DRM device - * @dev: DRM device - * - * This unplugs a hotpluggable DRM device, which makes it inaccessible to - * userspace operations. Entry-points can use drm_dev_enter() and - * drm_dev_exit() to protect device resources in a race free manner. This - * essentially unregisters the device like drm_dev_unregister(), but can be - * called while there are still open users of @dev. - */ -void drm_dev_unplug(struct drm_device *dev) -{ - drm_dev_unregister(dev); - drm_dev_put(dev); -} -EXPORT_SYMBOL(drm_dev_unplug); - /* * DRM internal mount * We want to be able to allocate our own "struct address_space" to control diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h index c50696c82a42..b8765a6fc092 100644 --- a/include/drm/drm_drv.h +++ b/include/drm/drm_drv.h @@ -730,7 +730,6 @@ void drm_dev_put(struct drm_device *dev); void drm_put_dev(struct drm_device *dev); bool drm_dev_enter(struct drm_device *dev, int *idx); void drm_dev_exit(int idx); -void drm_dev_unplug(struct drm_device *dev);
/** * drm_dev_is_unplugged - is a DRM device unplugged
On 2/3/19 5:42 PM, Noralf Trønnes wrote:
There are no users left.
Signed-off-by: Noralf Trønnes noralf@tronnes.org
Reviewed-by: Oleksandr Andrushchenko oleksandr_andrushchenko@epam.com
drivers/gpu/drm/drm_drv.c | 17 ----------------- include/drm/drm_drv.h | 1 - 2 files changed, 18 deletions(-)
diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c index e0941200edc6..87210d4a9e53 100644 --- a/drivers/gpu/drm/drm_drv.c +++ b/drivers/gpu/drm/drm_drv.c @@ -354,23 +354,6 @@ void drm_dev_exit(int idx) } EXPORT_SYMBOL(drm_dev_exit);
-/**
- drm_dev_unplug - unplug a DRM device
- @dev: DRM device
- This unplugs a hotpluggable DRM device, which makes it inaccessible to
- userspace operations. Entry-points can use drm_dev_enter() and
- drm_dev_exit() to protect device resources in a race free manner. This
- essentially unregisters the device like drm_dev_unregister(), but can be
- called while there are still open users of @dev.
- */
-void drm_dev_unplug(struct drm_device *dev) -{
- drm_dev_unregister(dev);
- drm_dev_put(dev);
-} -EXPORT_SYMBOL(drm_dev_unplug);
- /*
- DRM internal mount
- We want to be able to allocate our own "struct address_space" to control
diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h index c50696c82a42..b8765a6fc092 100644 --- a/include/drm/drm_drv.h +++ b/include/drm/drm_drv.h @@ -730,7 +730,6 @@ void drm_dev_put(struct drm_device *dev); void drm_put_dev(struct drm_device *dev); bool drm_dev_enter(struct drm_device *dev, int *idx); void drm_dev_exit(int idx); -void drm_dev_unplug(struct drm_device *dev);
/**
- drm_dev_is_unplugged - is a DRM device unplugged
On Sun, Feb 03, 2019 at 04:42:00PM +0100, Noralf Trønnes wrote:
There are no users left.
Signed-off-by: Noralf Trønnes noralf@tronnes.org
Reviewed-by: Sean Paul sean@poorly.run
drivers/gpu/drm/drm_drv.c | 17 ----------------- include/drm/drm_drv.h | 1 - 2 files changed, 18 deletions(-)
diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c index e0941200edc6..87210d4a9e53 100644 --- a/drivers/gpu/drm/drm_drv.c +++ b/drivers/gpu/drm/drm_drv.c @@ -354,23 +354,6 @@ void drm_dev_exit(int idx) } EXPORT_SYMBOL(drm_dev_exit);
-/**
- drm_dev_unplug - unplug a DRM device
- @dev: DRM device
- This unplugs a hotpluggable DRM device, which makes it inaccessible to
- userspace operations. Entry-points can use drm_dev_enter() and
- drm_dev_exit() to protect device resources in a race free manner. This
- essentially unregisters the device like drm_dev_unregister(), but can be
- called while there are still open users of @dev.
- */
-void drm_dev_unplug(struct drm_device *dev) -{
- drm_dev_unregister(dev);
- drm_dev_put(dev);
-} -EXPORT_SYMBOL(drm_dev_unplug);
/*
- DRM internal mount
- We want to be able to allocate our own "struct address_space" to control
diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h index c50696c82a42..b8765a6fc092 100644 --- a/include/drm/drm_drv.h +++ b/include/drm/drm_drv.h @@ -730,7 +730,6 @@ void drm_dev_put(struct drm_device *dev); void drm_put_dev(struct drm_device *dev); bool drm_dev_enter(struct drm_device *dev, int *idx); void drm_dev_exit(int idx); -void drm_dev_unplug(struct drm_device *dev);
/**
- drm_dev_is_unplugged - is a DRM device unplugged
-- 2.20.1
On Sun, Feb 03, 2019 at 04:41:54PM +0100, Noralf Trønnes wrote:
This series removes drm_dev_unplug() and moves the unplugged state setting to drm_dev_unregister(). All drivers will now have access to the unplugged state if they so desire.
The drm_device ref handling wrt to the last fd closed after unregister have been simplified, which also fixed a double drm_dev_unregister() situation.
Nice. On the series:
Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch
But definitely wait 1-2 weeks for some more driver acks I'd say before applying this all. -Daniel
Noralf.
Noralf Trønnes (6): drm: Fix drm_release() and device unplug drm/drv: Prepare to remove drm_dev_unplug() drm/amd: Use drm_dev_unregister() drm/udl: Use drm_dev_unregister() drm/xen: Use drm_dev_unregister() drm/drv: Remove drm_dev_unplug()
drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c | 3 +- drivers/gpu/drm/drm_drv.c | 48 ++++++++----------------- drivers/gpu/drm/drm_file.c | 6 ++-- drivers/gpu/drm/udl/udl_drv.c | 3 +- drivers/gpu/drm/xen/xen_drm_front.c | 7 ++-- include/drm/drm_drv.h | 11 +++--- 6 files changed, 27 insertions(+), 51 deletions(-)
-- 2.20.1
dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
Adding Andrey who looked into cleaning this up a while ago as well.
Christian.
Am 03.02.19 um 16:41 schrieb Noralf Trønnes:
This series removes drm_dev_unplug() and moves the unplugged state setting to drm_dev_unregister(). All drivers will now have access to the unplugged state if they so desire.
The drm_device ref handling wrt to the last fd closed after unregister have been simplified, which also fixed a double drm_dev_unregister() situation.
Noralf.
Noralf Trønnes (6): drm: Fix drm_release() and device unplug drm/drv: Prepare to remove drm_dev_unplug() drm/amd: Use drm_dev_unregister() drm/udl: Use drm_dev_unregister() drm/xen: Use drm_dev_unregister() drm/drv: Remove drm_dev_unplug()
drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c | 3 +- drivers/gpu/drm/drm_drv.c | 48 ++++++++----------------- drivers/gpu/drm/drm_file.c | 6 ++-- drivers/gpu/drm/udl/udl_drv.c | 3 +- drivers/gpu/drm/xen/xen_drm_front.c | 7 ++-- include/drm/drm_drv.h | 11 +++--- 6 files changed, 27 insertions(+), 51 deletions(-)
dri-devel@lists.freedesktop.org
-
Daniel Vetter -
Eric Anholt -
Koenig, Christian -
Noralf Trønnes -
Oleksandr Andrushchenko -
Sean Paul