drm_device.master_mutex currently protects the following: - drm_device.master - drm_file.master - drm_file.was_master - drm_file.is_master
These attributes determine modesetting permissions for drm devices, and there is a clear separation between functions that read or change the permissions. Hence, convert master_mutex into a rwsem to enable concurrent readers.
Signed-off-by: Desmond Cheong Zhi Xi desmondcheongzx@gmail.com --- drivers/gpu/drm/drm_auth.c | 27 ++++++++++++++------------- drivers/gpu/drm/drm_debugfs.c | 4 ++-- drivers/gpu/drm/drm_drv.c | 3 +-- drivers/gpu/drm/drm_ioctl.c | 4 ++-- include/drm/drm_device.h | 11 +++++++---- include/drm/drm_file.h | 12 ++++++------ 6 files changed, 32 insertions(+), 29 deletions(-)
diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c index 0acb444fbbac..b65681ff42fc 100644 --- a/drivers/gpu/drm/drm_auth.c +++ b/drivers/gpu/drm/drm_auth.c @@ -64,7 +64,7 @@ static bool drm_is_current_master_locked(struct drm_file *fpriv) { lockdep_assert_once(lockdep_is_held(&fpriv->minor->dev->master_lookup_lock) || - lockdep_is_held(&fpriv->minor->dev->master_mutex)); + lockdep_is_held(&fpriv->minor->dev->master_rwsem));
return (fpriv->is_master && fpriv->master && drm_lease_owner(fpriv->master) == fpriv->minor->dev->master); @@ -175,7 +175,7 @@ static int drm_new_set_master(struct drm_device *dev, struct drm_file *fpriv) struct drm_master *old_master; struct drm_master *new_master;
- lockdep_assert_held_once(&dev->master_mutex); + lockdep_assert_held_once(&dev->master_rwsem);
WARN_ON(fpriv->is_master); old_master = fpriv->master; @@ -257,7 +257,7 @@ int drm_setmaster_ioctl(struct drm_device *dev, void *data, { int ret;
- mutex_lock(&dev->master_mutex); + down_write(&dev->master_rwsem);
ret = drm_master_check_perm(dev, file_priv); if (ret) @@ -289,7 +289,7 @@ int drm_setmaster_ioctl(struct drm_device *dev, void *data,
drm_set_master(dev, file_priv, false); out_unlock: - mutex_unlock(&dev->master_mutex); + up_write(&dev->master_rwsem); return ret; }
@@ -306,7 +306,7 @@ int drm_dropmaster_ioctl(struct drm_device *dev, void *data, { int ret;
- mutex_lock(&dev->master_mutex); + down_write(&dev->master_rwsem);
ret = drm_master_check_perm(dev, file_priv); if (ret) @@ -329,8 +329,9 @@ int drm_dropmaster_ioctl(struct drm_device *dev, void *data, }
drm_drop_master(dev, file_priv); + out_unlock: - mutex_unlock(&dev->master_mutex); + up_write(&dev->master_rwsem); return ret; }
@@ -342,7 +343,7 @@ int drm_master_open(struct drm_file *file_priv) /* if there is no current master make this fd it, but do not create * any master object for render clients */ - mutex_lock(&dev->master_mutex); + down_write(&dev->master_rwsem); if (!dev->master) { ret = drm_new_set_master(dev, file_priv); } else { @@ -350,7 +351,7 @@ int drm_master_open(struct drm_file *file_priv) file_priv->master = drm_master_get(dev->master); spin_unlock(&dev->master_lookup_lock); } - mutex_unlock(&dev->master_mutex); + up_write(&dev->master_rwsem);
return ret; } @@ -360,7 +361,7 @@ void drm_master_release(struct drm_file *file_priv) struct drm_device *dev = file_priv->minor->dev; struct drm_master *master;
- mutex_lock(&dev->master_mutex); + down_write(&dev->master_rwsem); master = file_priv->master;
if (!master) @@ -393,7 +394,7 @@ void drm_master_release(struct drm_file *file_priv) spin_unlock(&dev->master_lookup_lock); } unlock: - mutex_unlock(&dev->master_mutex); + up_write(&dev->master_rwsem); }
/** @@ -468,9 +469,9 @@ EXPORT_SYMBOL(drm_master_put); /* Used by drm_client and drm_fb_helper */ bool drm_master_internal_acquire(struct drm_device *dev) { - mutex_lock(&dev->master_mutex); + down_read(&dev->master_rwsem); if (dev->master) { - mutex_unlock(&dev->master_mutex); + up_read(&dev->master_rwsem); return false; }
@@ -481,6 +482,6 @@ EXPORT_SYMBOL(drm_master_internal_acquire); /* Used by drm_client and drm_fb_helper */ void drm_master_internal_release(struct drm_device *dev) { - mutex_unlock(&dev->master_mutex); + up_read(&dev->master_rwsem); } EXPORT_SYMBOL(drm_master_internal_release); diff --git a/drivers/gpu/drm/drm_debugfs.c b/drivers/gpu/drm/drm_debugfs.c index b0a826489488..b34c9c263188 100644 --- a/drivers/gpu/drm/drm_debugfs.c +++ b/drivers/gpu/drm/drm_debugfs.c @@ -55,7 +55,7 @@ static int drm_name_info(struct seq_file *m, void *data) struct drm_device *dev = minor->dev; struct drm_master *master;
- mutex_lock(&dev->master_mutex); + down_read(&dev->master_rwsem); master = dev->master; seq_printf(m, "%s", dev->driver->name); if (dev->dev) @@ -65,7 +65,7 @@ static int drm_name_info(struct seq_file *m, void *data) if (dev->unique) seq_printf(m, " unique=%s", dev->unique); seq_printf(m, "\n"); - mutex_unlock(&dev->master_mutex); + up_read(&dev->master_rwsem);
return 0; } diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c index 218c16f11c80..d61079ae6259 100644 --- a/drivers/gpu/drm/drm_drv.c +++ b/drivers/gpu/drm/drm_drv.c @@ -570,7 +570,6 @@ static void drm_dev_init_release(struct drm_device *dev, void *res) /* Prevent use-after-free in drm_managed_release when debugging is * enabled. Slightly awkward, but can't really be helped. */ dev->dev = NULL; - mutex_destroy(&dev->master_mutex); mutex_destroy(&dev->clientlist_mutex); mutex_destroy(&dev->filelist_mutex); mutex_destroy(&dev->struct_mutex); @@ -611,7 +610,7 @@ static int drm_dev_init(struct drm_device *dev, mutex_init(&dev->struct_mutex); mutex_init(&dev->filelist_mutex); mutex_init(&dev->clientlist_mutex); - mutex_init(&dev->master_mutex); + init_rwsem(&dev->master_rwsem); spin_lock_init(&dev->master_lookup_lock);
ret = drmm_add_action(dev, drm_dev_init_release, NULL); diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c index e5c3845b6e62..880fc565d599 100644 --- a/drivers/gpu/drm/drm_ioctl.c +++ b/drivers/gpu/drm/drm_ioctl.c @@ -390,7 +390,7 @@ static int drm_setversion(struct drm_device *dev, void *data, struct drm_file *f struct drm_set_version *sv = data; int if_version, retcode = 0;
- mutex_lock(&dev->master_mutex); + down_read(&dev->master_rwsem); if (sv->drm_di_major != -1) { if (sv->drm_di_major != DRM_IF_MAJOR || sv->drm_di_minor < 0 || sv->drm_di_minor > DRM_IF_MINOR) { @@ -427,7 +427,7 @@ static int drm_setversion(struct drm_device *dev, void *data, struct drm_file *f sv->drm_di_minor = DRM_IF_MINOR; sv->drm_dd_major = dev->driver->major; sv->drm_dd_minor = dev->driver->minor; - mutex_unlock(&dev->master_mutex); + up_read(&dev->master_rwsem);
return retcode; } diff --git a/include/drm/drm_device.h b/include/drm/drm_device.h index cf5d15aeb25f..f1ae4570a20a 100644 --- a/include/drm/drm_device.h +++ b/include/drm/drm_device.h @@ -107,7 +107,7 @@ struct drm_device { * @master: * * Currently active master for this device. - * Protected by &master_mutex + * Protected by &master_rwsem */ struct drm_master *master;
@@ -146,11 +146,14 @@ struct drm_device { struct mutex struct_mutex;
/** - * @master_mutex: + * @master_rwsem: * - * Lock for &drm_minor.master and &drm_file.is_master + * Synchronizes modesetting rights between multiple users. Users that + * can change the modeset or display state must hold a read lock on + * @master_rwsem, and users that change modesetting rights should hold + * a write lock. */ - struct mutex master_mutex; + struct rw_semaphore master_rwsem;
/** * @master_lookup_lock: diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h index 0536e9612a46..ce213ac23c38 100644 --- a/include/drm/drm_file.h +++ b/include/drm/drm_file.h @@ -205,7 +205,7 @@ struct drm_file { * @was_master: * * This client has or had, master capability. Protected by struct - * &drm_device.master_mutex. + * &drm_device.master_rwsem. * * This is used to ensure that CAP_SYS_ADMIN is not enforced, if the * client is or was master in the past. @@ -216,7 +216,7 @@ struct drm_file { * @is_master: * * This client is the creator of @master. Protected by struct - * &drm_device.master_mutex. + * &drm_device.master_rwsem. * * See also the :ref:`section on primary nodes and authentication * <drm_primary_node>`. @@ -227,20 +227,20 @@ struct drm_file { * @master: * * Master this node is currently associated with. Protected by struct - * &drm_device.master_mutex, and serialized by + * &drm_device.master_rwsem, and serialized by * &drm_device.master_lookup_lock. * * Only relevant if drm_is_primary_client() returns true. Note that * this only matches &drm_device.master if the master is the currently * active one. * - * To update @master, both &drm_device.master_mutex and + * To update @master, both &drm_device.master_rwsem and * &drm_device.master_lookup_lock need to be held, therefore holding * either of them is safe and enough for the read side. * * When dereferencing this pointer, either hold struct - * &drm_device.master_mutex for the duration of the pointer's use, or - * use drm_file_get_master() if struct &drm_device.master_mutex is not + * &drm_device.master_rwsem for the duration of the pointer's use, or + * use drm_file_get_master() if struct &drm_device.master_rwsem is not * currently held and there is no other need to hold it. This prevents * @master from being freed during use. *