Previously, master_lookup_lock was introduced in commit 0b0860a3cf5e ("drm: serialize drm_file.master with a new spinlock") to serialize accesses to drm_file.master. This then allowed us to write drm_file_get_master in commit 56f0729a510f ("drm: protect drm_master pointers in drm_lease.c").
The rationale behind introducing a new spinlock at the time was that the other lock that could have been used (drm_device.master_mutex) was the outermost lock, so embedding calls to drm_file_get_master in various functions easily caused us to invert the lock hierarchy. For example, we would invert the master_mutex --> mode_config.idr_mutex hierarchy.
Following the conversion of master_mutex into a rwsem, and its use to plug races with modesetting rights, we've untangled some lock hierarchies and removed the need for using drm_file_get_master and the unlocked version of drm_is_current_master in multiple places.
Hence, we can take this opportunity to clean up the locking design. To do so, we rewrite drm_file_get_master and drm_is_current_master to use master_rwsem, clean up their uses, fix remaining inversions (such as with _drm_lease_held master grabbing master_rwsem while holding onto mode_config.idr_mutex), then remove master_lookup_lock.
Signed-off-by: Desmond Cheong Zhi Xi desmondcheongzx@gmail.com --- drivers/gpu/drm/drm_auth.c | 19 ++++++---------- drivers/gpu/drm/drm_file.c | 1 - drivers/gpu/drm/drm_internal.h | 1 + drivers/gpu/drm/drm_ioctl.c | 4 ++-- drivers/gpu/drm/drm_lease.c | 38 ++++++++----------------------- drivers/gpu/drm/drm_mode_object.c | 14 +++++++++--- include/drm/drm_file.h | 9 +------- include/drm/drm_lease.h | 2 +- 8 files changed, 32 insertions(+), 56 deletions(-)
diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c index 65065f7e1499..ff720f67eacb 100644 --- a/drivers/gpu/drm/drm_auth.c +++ b/drivers/gpu/drm/drm_auth.c @@ -61,10 +61,9 @@ * trusted clients. */
-static bool drm_is_current_master_locked(struct drm_file *fpriv) +bool drm_is_current_master_locked(struct drm_file *fpriv) { - lockdep_assert_once(lockdep_is_held(&fpriv->master_lookup_lock) || - lockdep_is_held(&fpriv->minor->dev->master_rwsem)); + lockdep_assert_held_once(&fpriv->minor->dev->master_rwsem);
return fpriv->is_master && drm_lease_owner(fpriv->master) == fpriv->minor->dev->master; } @@ -83,9 +82,9 @@ bool drm_is_current_master(struct drm_file *fpriv) { bool ret;
- spin_lock(&fpriv->master_lookup_lock); + down_read(&fpriv->minor->dev->master_rwsem); ret = drm_is_current_master_locked(fpriv); - spin_unlock(&fpriv->master_lookup_lock); + up_read(&fpriv->minor->dev->master_rwsem);
return ret; } @@ -120,7 +119,7 @@ int drm_authmagic(struct drm_device *dev, void *data, DRM_DEBUG("%u\n", auth->magic);
down_write(&dev->master_rwsem); - if (unlikely(!drm_is_current_master(file_priv))) { + if (unlikely(!drm_is_current_master_locked(file_priv))) { up_write(&dev->master_rwsem); return -EACCES; } @@ -178,9 +177,7 @@ static int drm_new_set_master(struct drm_device *dev, struct drm_file *fpriv) new_master = drm_master_create(dev); if (!new_master) return -ENOMEM; - spin_lock(&fpriv->master_lookup_lock); fpriv->master = new_master; - spin_unlock(&fpriv->master_lookup_lock);
fpriv->is_master = 1; fpriv->authenticated = 1; @@ -343,9 +340,7 @@ int drm_master_open(struct drm_file *file_priv) if (!dev->master) { ret = drm_new_set_master(dev, file_priv); } else { - spin_lock(&file_priv->master_lookup_lock); file_priv->master = drm_master_get(dev->master); - spin_unlock(&file_priv->master_lookup_lock); } up_write(&dev->master_rwsem);
@@ -410,13 +405,13 @@ struct drm_master *drm_file_get_master(struct drm_file *file_priv) { struct drm_master *master = NULL;
- spin_lock(&file_priv->master_lookup_lock); + down_read(&file_priv->minor->dev->master_rwsem); if (!file_priv->master) goto unlock; master = drm_master_get(file_priv->master);
unlock: - spin_unlock(&file_priv->master_lookup_lock); + up_read(&file_priv->minor->dev->master_rwsem); return master; } EXPORT_SYMBOL(drm_file_get_master); diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c index 90b62f360da1..8c846e0179d7 100644 --- a/drivers/gpu/drm/drm_file.c +++ b/drivers/gpu/drm/drm_file.c @@ -176,7 +176,6 @@ struct drm_file *drm_file_alloc(struct drm_minor *minor) init_waitqueue_head(&file->event_wait); file->event_space = 4096; /* set aside 4k for event buffer */
- spin_lock_init(&file->master_lookup_lock); mutex_init(&file->event_read_lock);
if (drm_core_check_feature(dev, DRIVER_GEM)) diff --git a/drivers/gpu/drm/drm_internal.h b/drivers/gpu/drm/drm_internal.h index 17f3548c8ed2..5d421f749a17 100644 --- a/drivers/gpu/drm/drm_internal.h +++ b/drivers/gpu/drm/drm_internal.h @@ -132,6 +132,7 @@ int drm_crtc_queue_sequence_ioctl(struct drm_device *dev, void *data, struct drm_file *filp);
/* drm_auth.c */ +bool drm_is_current_master_locked(struct drm_file *fpriv); int drm_getmagic(struct drm_device *dev, void *data, struct drm_file *file_priv); int drm_authmagic(struct drm_device *dev, void *data, diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c index 8bea39ffc5c0..c728437466c3 100644 --- a/drivers/gpu/drm/drm_ioctl.c +++ b/drivers/gpu/drm/drm_ioctl.c @@ -386,7 +386,7 @@ static int drm_setversion(struct drm_device *dev, void *data, struct drm_file *f int if_version, retcode = 0;
down_write(&dev->master_rwsem); - if (unlikely(!drm_is_current_master(file_priv))) { + if (unlikely(!drm_is_current_master_locked(file_priv))) { retcode = -EACCES; goto unlock; } @@ -540,7 +540,7 @@ static int drm_ioctl_permit(u32 flags, struct drm_file *file_priv)
/* MASTER is only for master or control clients */ if (unlikely((flags & DRM_MASTER) && - !drm_is_current_master(file_priv))) + !drm_is_current_master_locked(file_priv))) return -EACCES;
/* Render clients must be explicitly allowed */ diff --git a/drivers/gpu/drm/drm_lease.c b/drivers/gpu/drm/drm_lease.c index bed6f7636cbe..c515d40f32c0 100644 --- a/drivers/gpu/drm/drm_lease.c +++ b/drivers/gpu/drm/drm_lease.c @@ -85,7 +85,7 @@ _drm_find_lessee(struct drm_master *master, int lessee_id) return idr_find(&drm_lease_owner(master)->lessee_idr, lessee_id); }
-static int _drm_lease_held_master(struct drm_master *master, int id) +bool _drm_lease_held_master(struct drm_master *master, int id) { lockdep_assert_held(&master->dev->mode_config.idr_mutex); if (master->lessor) @@ -105,24 +105,6 @@ static bool _drm_has_leased(struct drm_master *master, int id) return false; }
-/* Called with idr_mutex held */ -bool _drm_lease_held(struct drm_file *file_priv, int id) -{ - bool ret; - struct drm_master *master; - - if (!file_priv) - return true; - - master = drm_file_get_master(file_priv); - if (!master) - return true; - ret = _drm_lease_held_master(master, id); - drm_master_put(&master); - - return ret; -} - bool drm_lease_held(struct drm_file *file_priv, int id) { struct drm_master *master; @@ -507,12 +489,12 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev, return PTR_ERR(lessee_file);
down_read(&dev->master_rwsem); - if (unlikely(!drm_is_current_master(lessor_priv))) { + if (unlikely(!drm_is_current_master_locked(lessor_priv))) { ret = -EACCES; goto out_file; }
- lessor = drm_file_get_master(lessor_priv); + lessor = lessor_priv->master; /* Do not allow sub-leases */ if (lessor->lessor) { DRM_DEBUG_LEASE("recursive leasing not allowed\n"); @@ -574,7 +556,6 @@ int drm_mode_create_lease_ioctl(struct drm_device *dev, /* Hook up the fd */ fd_install(fd, lessee_file);
- drm_master_put(&lessor); up_read(&dev->master_rwsem); DRM_DEBUG_LEASE("drm_mode_create_lease_ioctl succeeded\n"); return 0; @@ -609,7 +590,8 @@ int drm_mode_list_lessees_ioctl(struct drm_device *dev, if (!drm_core_check_feature(dev, DRIVER_MODESET)) return -EOPNOTSUPP;
- lessor = drm_file_get_master(lessor_priv); + lockdep_assert_held_once(&dev->master_rwsem); + lessor = lessor_priv->master; DRM_DEBUG_LEASE("List lessees for %d\n", lessor->lessee_id);
mutex_lock(&dev->mode_config.idr_mutex); @@ -633,7 +615,6 @@ int drm_mode_list_lessees_ioctl(struct drm_device *dev, arg->count_lessees = count;
mutex_unlock(&dev->mode_config.idr_mutex); - drm_master_put(&lessor);
return ret; } @@ -659,7 +640,8 @@ int drm_mode_get_lease_ioctl(struct drm_device *dev, if (!drm_core_check_feature(dev, DRIVER_MODESET)) return -EOPNOTSUPP;
- lessee = drm_file_get_master(lessee_priv); + lockdep_assert_held_once(&dev->master_rwsem); + lessee = lessee_priv->master; DRM_DEBUG_LEASE("get lease for %d\n", lessee->lessee_id);
mutex_lock(&dev->mode_config.idr_mutex); @@ -687,7 +669,6 @@ int drm_mode_get_lease_ioctl(struct drm_device *dev, arg->count_objects = count;
mutex_unlock(&dev->mode_config.idr_mutex); - drm_master_put(&lessee);
return ret; } @@ -712,11 +693,11 @@ int drm_mode_revoke_lease_ioctl(struct drm_device *dev, return -EOPNOTSUPP;
down_write(&dev->master_rwsem); - if (unlikely(!drm_is_current_master(lessor_priv))) { + if (unlikely(!drm_is_current_master_locked(lessor_priv))) { ret = -EACCES; goto unlock; } - lessor = drm_file_get_master(lessor_priv); + lessor = lessor_priv->master; mutex_lock(&dev->mode_config.idr_mutex);
lessee = _drm_find_lessee(lessor, arg->lessee_id); @@ -737,7 +718,6 @@ int drm_mode_revoke_lease_ioctl(struct drm_device *dev,
fail: mutex_unlock(&dev->mode_config.idr_mutex); - drm_master_put(&lessor);
unlock: up_write(&dev->master_rwsem); diff --git a/drivers/gpu/drm/drm_mode_object.c b/drivers/gpu/drm/drm_mode_object.c index 86d9e907c0b2..f15b81ea347a 100644 --- a/drivers/gpu/drm/drm_mode_object.c +++ b/drivers/gpu/drm/drm_mode_object.c @@ -29,6 +29,7 @@ #include <drm/drm_file.h> #include <drm/drm_mode_object.h> #include <drm/drm_print.h> +#include <drm/drm_auth.h>
#include "drm_crtc_internal.h"
@@ -138,6 +139,10 @@ struct drm_mode_object *__drm_mode_object_find(struct drm_device *dev, uint32_t id, uint32_t type) { struct drm_mode_object *obj = NULL; + struct drm_master *master = NULL; + + if (file_priv) + master = drm_file_get_master(file_priv);
mutex_lock(&dev->mode_config.idr_mutex); obj = idr_find(&dev->mode_config.object_idr, id); @@ -146,15 +151,18 @@ struct drm_mode_object *__drm_mode_object_find(struct drm_device *dev, if (obj && obj->id != id) obj = NULL;
- if (obj && drm_mode_object_lease_required(obj->type) && - !_drm_lease_held(file_priv, obj->id)) - obj = NULL; + if (obj && drm_mode_object_lease_required(obj->type)) { + if (master && !_drm_lease_held_master(master, obj->id)) + obj = NULL; + }
if (obj && obj->free_cb) { if (!kref_get_unless_zero(&obj->refcount)) obj = NULL; } mutex_unlock(&dev->mode_config.idr_mutex); + if (master) + drm_master_put(&master);
return obj; } diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h index d12bb2ba7814..e2d49fe3e32d 100644 --- a/include/drm/drm_file.h +++ b/include/drm/drm_file.h @@ -227,16 +227,12 @@ struct drm_file { * @master: * * Master this node is currently associated with. Protected by struct - * &drm_device.master_rwsem, and serialized by @master_lookup_lock. + * &drm_device.master_rwsem. * * 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_rwsem and - * @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_rwsem for the duration of the pointer's use, or * use drm_file_get_master() if struct &drm_device.master_rwsem is not @@ -248,9 +244,6 @@ struct drm_file { */ struct drm_master *master;
- /** @master_lock: Serializes @master. */ - spinlock_t master_lookup_lock; - /** @pid: Process that opened this file. */ struct pid *pid;
diff --git a/include/drm/drm_lease.h b/include/drm/drm_lease.h index 5c9ef6a2aeae..a5e47c54bfc3 100644 --- a/include/drm/drm_lease.h +++ b/include/drm/drm_lease.h @@ -16,7 +16,7 @@ void drm_lease_destroy(struct drm_master *lessee);
bool drm_lease_held(struct drm_file *file_priv, int id);
-bool _drm_lease_held(struct drm_file *file_priv, int id); +bool _drm_lease_held_master(struct drm_master *master, int id);
void drm_lease_revoke(struct drm_master *master);