| Message ID | 20240521071639.77614-16-thomas.hellstrom@linux.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | TTM shrinker helpers and xe buffer object shrinker | expand |
Am 21.05.24 um 09:16 schrieb Thomas Hellström: > When validating a buffer object for submission, we might need to lock > a number of object for eviction to make room for the validation. > > This makes it pretty likely that validation will eventually succeed, > since eventually the validating process will hold most dma_resv locks > of the buffer objects residing in the memory type being validated for. > > However, once validation of a single object has succeeded it might not > be beneficial to hold on to those locks anymore, and the validator > would want to drop the locks of all objects taken during validation. Exactly avoiding that was one of the goals of developing the drm_exec object. When objects are unlocked after evicting them it just gives concurrent operations an opportunity to lock them and re-validate them into the contended domain. So why should that approach here be beneficial at all? Regards, Christian. > > Introduce a drm_exec snapshot functionality that can be used to > record the locks held at a certain time, and a restore functionality > that restores the drm_exec state to the snapshot by dropping all > locks. > > Snapshots can be nested if needed. > > Cc: Christian König <christian.koenig@amd.com> > Cc: Somalapuram Amaranath <Amaranath.Somalapuram@amd.com> > Cc: Matthew Brost <matthew.brost@intel.com> > Cc: <dri-devel@lists.freedesktop.org> > Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com> > --- > drivers/gpu/drm/drm_exec.c | 55 +++++++++++++++++++++++++++++++++++++- > include/drm/drm_exec.h | 23 +++++++++++++++- > 2 files changed, 76 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/drm_exec.c b/drivers/gpu/drm/drm_exec.c > index 1383680ffa4a..9eea5d0d3a98 100644 > --- a/drivers/gpu/drm/drm_exec.c > +++ b/drivers/gpu/drm/drm_exec.c > @@ -57,6 +57,7 @@ static void drm_exec_unlock_all(struct drm_exec *exec) > struct drm_gem_object *obj; > unsigned long index; > > + WARN_ON(exec->snap); > drm_exec_for_each_locked_object_reverse(exec, index, obj) { > dma_resv_unlock(obj->resv); > drm_gem_object_put(obj); > @@ -90,6 +91,7 @@ void drm_exec_init(struct drm_exec *exec, u32 flags, unsigned nr) > exec->num_objects = 0; > exec->contended = DRM_EXEC_DUMMY; > exec->prelocked = NULL; > + exec->snap = NULL; > } > EXPORT_SYMBOL(drm_exec_init); > > @@ -301,7 +303,6 @@ int drm_exec_lock_obj(struct drm_exec *exec, struct drm_gem_object *obj) > goto error_unlock; > > return 0; > - > error_unlock: > dma_resv_unlock(obj->resv); > return ret; > @@ -395,5 +396,57 @@ int drm_exec_prepare_array(struct drm_exec *exec, > } > EXPORT_SYMBOL(drm_exec_prepare_array); > > +/** > + * drm_exec_restore() - Restore the drm_exec state to the point of a snapshot. > + * @exec: The drm_exec object with the state. > + * @snap: The snapshot state. > + * > + * Restores the drm_exec object by means of unlocking and dropping references > + * to objects locked after the snapshot. > + */ > +void drm_exec_restore(struct drm_exec *exec, struct drm_exec_snapshot *snap) > +{ > + struct drm_gem_object *obj; > + unsigned int index; > + > + exec->snap = snap->saved_snap; > + > + drm_exec_for_each_locked_object_reverse(exec, index, obj) { > + if (index + 1 == snap->num_locked) > + break; > + > + dma_resv_unlock(obj->resv); > + drm_gem_object_put(obj); > + exec->objects[index] = NULL; > + } > + > + exec->num_objects = snap->num_locked; > + > + if (!exec->prelocked) > + exec->prelocked = snap->prelocked; > + else > + drm_gem_object_put(snap->prelocked); > +} > +EXPORT_SYMBOL(drm_exec_restore); > + > +/** > + * drm_exec_snapshot() - Take a snapshot of the drm_exec state > + * @exec: The drm_exec object with the state. > + * @snap: The snapshot state. > + * > + * Records the @exec state in @snap. The @snap object is typically allocated > + * in the stack of the caller. > + */ > +void drm_exec_snapshot(struct drm_exec *exec, struct drm_exec_snapshot *snap) > +{ > + snap->num_locked = exec->num_objects; > + snap->prelocked = exec->prelocked; > + if (snap->prelocked) > + drm_gem_object_get(snap->prelocked); > + snap->saved_snap = exec->snap; > + exec->snap = snap; > +} > +EXPORT_SYMBOL(drm_exec_snapshot); > + > MODULE_DESCRIPTION("DRM execution context"); > MODULE_LICENSE("Dual MIT/GPL"); > diff --git a/include/drm/drm_exec.h b/include/drm/drm_exec.h > index ea0f2117ee0c..0ce4d749511b 100644 > --- a/include/drm/drm_exec.h > +++ b/include/drm/drm_exec.h > @@ -19,7 +19,6 @@ struct drm_exec { > * @flags: Flags to control locking behavior > */ > u32 flags; > - > /** > * @ticket: WW ticket used for acquiring locks > */ > @@ -49,6 +48,25 @@ struct drm_exec { > * @prelocked: already locked GEM object due to contention > */ > struct drm_gem_object *prelocked; > + > + /** > + * @snap: Pointer to the last snapshot taken or NULL if none. > + */ > + struct drm_exec_snapshot *snap; > +}; > + > +/** > + * struct drm_exec_snapshot - drm_exec snapshot information > + */ > +struct drm_exec_snapshot { > + /** @saved_snap: Pointer to the previous snapshot or NULL. */ > + struct drm_exec_snapshot *saved_snap; > + > + /** @prelocked: Refcounted pointer to the prelocked object at snapshot time. */ > + struct drm_gem_object *prelocked; > + > + /** @num_locked: Number of locked objects at snapshot time. */ > + unsigned long num_locked; > }; > > int drm_exec_handle_contended(struct drm_exec *exec); > @@ -160,5 +178,8 @@ int drm_exec_prepare_array(struct drm_exec *exec, > struct drm_gem_object **objects, > unsigned int num_objects, > unsigned int num_fences); > +void drm_exec_snapshot(struct drm_exec *exec, struct drm_exec_snapshot *snap); > +void drm_exec_restore(struct drm_exec *exec, struct drm_exec_snapshot *snap); > + > > #endif
On Wed, 2024-05-22 at 13:27 +0200, Christian König wrote: > Am 21.05.24 um 09:16 schrieb Thomas Hellström: > > When validating a buffer object for submission, we might need to > > lock > > a number of object for eviction to make room for the validation. > > > > This makes it pretty likely that validation will eventually > > succeed, > > since eventually the validating process will hold most dma_resv > > locks > > of the buffer objects residing in the memory type being validated > > for. > > > > However, once validation of a single object has succeeded it might > > not > > be beneficial to hold on to those locks anymore, and the validator > > would want to drop the locks of all objects taken during > > validation. > > Exactly avoiding that was one of the goals of developing the drm_exec > object. > > When objects are unlocked after evicting them it just gives > concurrent > operations an opportunity to lock them and re-validate them into the > contended domain. > > So why should that approach here be beneficial at all? It's a matter of being nice to the rest of the system while *still guaranteeing progress*. For each object we're trying to validate, we keep on evicting other objects until we make progress even if we lock all the objects in the domain. If we were unlocking after each eviction, we can't really guarantee progress. OTOH, a concurrent locker of the object may well be one with higher priority (lower ticket number) just wanting to perform a pagefault So it's a tradeoff between locking just locking other processes out to allow us to make one step of progress and to in addition hit them with the big sledgehammer. /Thomas > > Regards, > Christian. > > > > > Introduce a drm_exec snapshot functionality that can be used to > > record the locks held at a certain time, and a restore > > functionality > > that restores the drm_exec state to the snapshot by dropping all > > locks. > > > > Snapshots can be nested if needed. > > > > Cc: Christian König <christian.koenig@amd.com> > > Cc: Somalapuram Amaranath <Amaranath.Somalapuram@amd.com> > > Cc: Matthew Brost <matthew.brost@intel.com> > > Cc: <dri-devel@lists.freedesktop.org> > > Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com> > > --- > > drivers/gpu/drm/drm_exec.c | 55 > > +++++++++++++++++++++++++++++++++++++- > > include/drm/drm_exec.h | 23 +++++++++++++++- > > 2 files changed, 76 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/gpu/drm/drm_exec.c > > b/drivers/gpu/drm/drm_exec.c > > index 1383680ffa4a..9eea5d0d3a98 100644 > > --- a/drivers/gpu/drm/drm_exec.c > > +++ b/drivers/gpu/drm/drm_exec.c > > @@ -57,6 +57,7 @@ static void drm_exec_unlock_all(struct drm_exec > > *exec) > > struct drm_gem_object *obj; > > unsigned long index; > > > > + WARN_ON(exec->snap); > > drm_exec_for_each_locked_object_reverse(exec, index, obj) > > { > > dma_resv_unlock(obj->resv); > > drm_gem_object_put(obj); > > @@ -90,6 +91,7 @@ void drm_exec_init(struct drm_exec *exec, u32 > > flags, unsigned nr) > > exec->num_objects = 0; > > exec->contended = DRM_EXEC_DUMMY; > > exec->prelocked = NULL; > > + exec->snap = NULL; > > } > > EXPORT_SYMBOL(drm_exec_init); > > > > @@ -301,7 +303,6 @@ int drm_exec_lock_obj(struct drm_exec *exec, > > struct drm_gem_object *obj) > > goto error_unlock; > > > > return 0; > > - > > error_unlock: > > dma_resv_unlock(obj->resv); > > return ret; > > @@ -395,5 +396,57 @@ int drm_exec_prepare_array(struct drm_exec > > *exec, > > } > > EXPORT_SYMBOL(drm_exec_prepare_array); > > > > +/** > > + * drm_exec_restore() - Restore the drm_exec state to the point of > > a snapshot. > > + * @exec: The drm_exec object with the state. > > + * @snap: The snapshot state. > > + * > > + * Restores the drm_exec object by means of unlocking and dropping > > references > > + * to objects locked after the snapshot. > > + */ > > +void drm_exec_restore(struct drm_exec *exec, struct > > drm_exec_snapshot *snap) > > +{ > > + struct drm_gem_object *obj; > > + unsigned int index; > > + > > + exec->snap = snap->saved_snap; > > + > > + drm_exec_for_each_locked_object_reverse(exec, index, obj) > > { > > + if (index + 1 == snap->num_locked) > > + break; > > + > > + dma_resv_unlock(obj->resv); > > + drm_gem_object_put(obj); > > + exec->objects[index] = NULL; > > + } > > + > > + exec->num_objects = snap->num_locked; > > + > > + if (!exec->prelocked) > > + exec->prelocked = snap->prelocked; > > + else > > + drm_gem_object_put(snap->prelocked); > > +} > > +EXPORT_SYMBOL(drm_exec_restore); > > + > > +/** > > + * drm_exec_snapshot() - Take a snapshot of the drm_exec state > > + * @exec: The drm_exec object with the state. > > + * @snap: The snapshot state. > > + * > > + * Records the @exec state in @snap. The @snap object is typically > > allocated > > + * in the stack of the caller. > > + */ > > +void drm_exec_snapshot(struct drm_exec *exec, struct > > drm_exec_snapshot *snap) > > +{ > > + snap->num_locked = exec->num_objects; > > + snap->prelocked = exec->prelocked; > > + if (snap->prelocked) > > + drm_gem_object_get(snap->prelocked); > > + snap->saved_snap = exec->snap; > > + exec->snap = snap; > > +} > > +EXPORT_SYMBOL(drm_exec_snapshot); > > + > > MODULE_DESCRIPTION("DRM execution context"); > > MODULE_LICENSE("Dual MIT/GPL"); > > diff --git a/include/drm/drm_exec.h b/include/drm/drm_exec.h > > index ea0f2117ee0c..0ce4d749511b 100644 > > --- a/include/drm/drm_exec.h > > +++ b/include/drm/drm_exec.h > > @@ -19,7 +19,6 @@ struct drm_exec { > > * @flags: Flags to control locking behavior > > */ > > u32 flags; > > - > > /** > > * @ticket: WW ticket used for acquiring locks > > */ > > @@ -49,6 +48,25 @@ struct drm_exec { > > * @prelocked: already locked GEM object due to contention > > */ > > struct drm_gem_object *prelocked; > > + > > + /** > > + * @snap: Pointer to the last snapshot taken or NULL if > > none. > > + */ > > + struct drm_exec_snapshot *snap; > > +}; > > + > > +/** > > + * struct drm_exec_snapshot - drm_exec snapshot information > > + */ > > +struct drm_exec_snapshot { > > + /** @saved_snap: Pointer to the previous snapshot or NULL. > > */ > > + struct drm_exec_snapshot *saved_snap; > > + > > + /** @prelocked: Refcounted pointer to the prelocked object > > at snapshot time. */ > > + struct drm_gem_object *prelocked; > > + > > + /** @num_locked: Number of locked objects at snapshot > > time. */ > > + unsigned long num_locked; > > }; > > > > int drm_exec_handle_contended(struct drm_exec *exec); > > @@ -160,5 +178,8 @@ int drm_exec_prepare_array(struct drm_exec > > *exec, > > struct drm_gem_object **objects, > > unsigned int num_objects, > > unsigned int num_fences); > > +void drm_exec_snapshot(struct drm_exec *exec, struct > > drm_exec_snapshot *snap); > > +void drm_exec_restore(struct drm_exec *exec, struct > > drm_exec_snapshot *snap); > > + > > > > #endif >
On Wed, 2024-05-22 at 15:54 +0200, Thomas Hellström wrote: > On Wed, 2024-05-22 at 13:27 +0200, Christian König wrote: > > Am 21.05.24 um 09:16 schrieb Thomas Hellström: > > > When validating a buffer object for submission, we might need to > > > lock > > > a number of object for eviction to make room for the validation. > > > > > > This makes it pretty likely that validation will eventually > > > succeed, > > > since eventually the validating process will hold most dma_resv > > > locks > > > of the buffer objects residing in the memory type being validated > > > for. > > > > > > However, once validation of a single object has succeeded it > > > might > > > not > > > be beneficial to hold on to those locks anymore, and the > > > validator > > > would want to drop the locks of all objects taken during > > > validation. > > > > Exactly avoiding that was one of the goals of developing the > > drm_exec > > object. > > > > When objects are unlocked after evicting them it just gives > > concurrent > > operations an opportunity to lock them and re-validate them into > > the > > contended domain. > > > > So why should that approach here be beneficial at all? > > It's a matter of being nice to the rest of the system while *still > guaranteeing progress*. For each object we're trying to validate, we > keep on evicting other objects until we make progress even if we lock > all the objects in the domain. > > If we were unlocking after each eviction, we can't really guarantee > progress. > > OTOH, a concurrent locker of the object may well be one with higher > priority (lower ticket number) just wanting to perform a pagefault > > So it's a tradeoff between locking just locking other processes out > to > allow us to make one step of progress and to in addition hit them > with > the big sledgehammer. I thought I'd also mention that the ideal solution here I think would be to have an rw_mutex per manager. Ordinary allocations take it in read mode, evictions take it in write mode. Now the bad thing is it sits in between ww_mutexes so it would have to be a ww_rw_mutex which would probably be too nasty to implement. /Thomas > > /Thomas > > > > > Regards, > > Christian. > > > > > > > > Introduce a drm_exec snapshot functionality that can be used to > > > record the locks held at a certain time, and a restore > > > functionality > > > that restores the drm_exec state to the snapshot by dropping all > > > locks. > > > > > > Snapshots can be nested if needed. > > > > > > Cc: Christian König <christian.koenig@amd.com> > > > Cc: Somalapuram Amaranath <Amaranath.Somalapuram@amd.com> > > > Cc: Matthew Brost <matthew.brost@intel.com> > > > Cc: <dri-devel@lists.freedesktop.org> > > > Signed-off-by: Thomas Hellström > > > <thomas.hellstrom@linux.intel.com> > > > --- > > > drivers/gpu/drm/drm_exec.c | 55 > > > +++++++++++++++++++++++++++++++++++++- > > > include/drm/drm_exec.h | 23 +++++++++++++++- > > > 2 files changed, 76 insertions(+), 2 deletions(-) > > > > > > diff --git a/drivers/gpu/drm/drm_exec.c > > > b/drivers/gpu/drm/drm_exec.c > > > index 1383680ffa4a..9eea5d0d3a98 100644 > > > --- a/drivers/gpu/drm/drm_exec.c > > > +++ b/drivers/gpu/drm/drm_exec.c > > > @@ -57,6 +57,7 @@ static void drm_exec_unlock_all(struct drm_exec > > > *exec) > > > struct drm_gem_object *obj; > > > unsigned long index; > > > > > > + WARN_ON(exec->snap); > > > drm_exec_for_each_locked_object_reverse(exec, index, > > > obj) > > > { > > > dma_resv_unlock(obj->resv); > > > drm_gem_object_put(obj); > > > @@ -90,6 +91,7 @@ void drm_exec_init(struct drm_exec *exec, u32 > > > flags, unsigned nr) > > > exec->num_objects = 0; > > > exec->contended = DRM_EXEC_DUMMY; > > > exec->prelocked = NULL; > > > + exec->snap = NULL; > > > } > > > EXPORT_SYMBOL(drm_exec_init); > > > > > > @@ -301,7 +303,6 @@ int drm_exec_lock_obj(struct drm_exec *exec, > > > struct drm_gem_object *obj) > > > goto error_unlock; > > > > > > return 0; > > > - > > > error_unlock: > > > dma_resv_unlock(obj->resv); > > > return ret; > > > @@ -395,5 +396,57 @@ int drm_exec_prepare_array(struct drm_exec > > > *exec, > > > } > > > EXPORT_SYMBOL(drm_exec_prepare_array); > > > > > > +/** > > > + * drm_exec_restore() - Restore the drm_exec state to the point > > > of > > > a snapshot. > > > + * @exec: The drm_exec object with the state. > > > + * @snap: The snapshot state. > > > + * > > > + * Restores the drm_exec object by means of unlocking and > > > dropping > > > references > > > + * to objects locked after the snapshot. > > > + */ > > > +void drm_exec_restore(struct drm_exec *exec, struct > > > drm_exec_snapshot *snap) > > > +{ > > > + struct drm_gem_object *obj; > > > + unsigned int index; > > > + > > > + exec->snap = snap->saved_snap; > > > + > > > + drm_exec_for_each_locked_object_reverse(exec, index, > > > obj) > > > { > > > + if (index + 1 == snap->num_locked) > > > + break; > > > + > > > + dma_resv_unlock(obj->resv); > > > + drm_gem_object_put(obj); > > > + exec->objects[index] = NULL; > > > + } > > > + > > > + exec->num_objects = snap->num_locked; > > > + > > > + if (!exec->prelocked) > > > + exec->prelocked = snap->prelocked; > > > + else > > > + drm_gem_object_put(snap->prelocked); > > > +} > > > +EXPORT_SYMBOL(drm_exec_restore); > > > + > > > +/** > > > + * drm_exec_snapshot() - Take a snapshot of the drm_exec state > > > + * @exec: The drm_exec object with the state. > > > + * @snap: The snapshot state. > > > + * > > > + * Records the @exec state in @snap. The @snap object is > > > typically > > > allocated > > > + * in the stack of the caller. > > > + */ > > > +void drm_exec_snapshot(struct drm_exec *exec, struct > > > drm_exec_snapshot *snap) > > > +{ > > > + snap->num_locked = exec->num_objects; > > > + snap->prelocked = exec->prelocked; > > > + if (snap->prelocked) > > > + drm_gem_object_get(snap->prelocked); > > > + snap->saved_snap = exec->snap; > > > + exec->snap = snap; > > > +} > > > +EXPORT_SYMBOL(drm_exec_snapshot); > > > + > > > MODULE_DESCRIPTION("DRM execution context"); > > > MODULE_LICENSE("Dual MIT/GPL"); > > > diff --git a/include/drm/drm_exec.h b/include/drm/drm_exec.h > > > index ea0f2117ee0c..0ce4d749511b 100644 > > > --- a/include/drm/drm_exec.h > > > +++ b/include/drm/drm_exec.h > > > @@ -19,7 +19,6 @@ struct drm_exec { > > > * @flags: Flags to control locking behavior > > > */ > > > u32 flags; > > > - > > > /** > > > * @ticket: WW ticket used for acquiring locks > > > */ > > > @@ -49,6 +48,25 @@ struct drm_exec { > > > * @prelocked: already locked GEM object due to > > > contention > > > */ > > > struct drm_gem_object *prelocked; > > > + > > > + /** > > > + * @snap: Pointer to the last snapshot taken or NULL if > > > none. > > > + */ > > > + struct drm_exec_snapshot *snap; > > > +}; > > > + > > > +/** > > > + * struct drm_exec_snapshot - drm_exec snapshot information > > > + */ > > > +struct drm_exec_snapshot { > > > + /** @saved_snap: Pointer to the previous snapshot or > > > NULL. > > > */ > > > + struct drm_exec_snapshot *saved_snap; > > > + > > > + /** @prelocked: Refcounted pointer to the prelocked > > > object > > > at snapshot time. */ > > > + struct drm_gem_object *prelocked; > > > + > > > + /** @num_locked: Number of locked objects at snapshot > > > time. */ > > > + unsigned long num_locked; > > > }; > > > > > > int drm_exec_handle_contended(struct drm_exec *exec); > > > @@ -160,5 +178,8 @@ int drm_exec_prepare_array(struct drm_exec > > > *exec, > > > struct drm_gem_object **objects, > > > unsigned int num_objects, > > > unsigned int num_fences); > > > +void drm_exec_snapshot(struct drm_exec *exec, struct > > > drm_exec_snapshot *snap); > > > +void drm_exec_restore(struct drm_exec *exec, struct > > > drm_exec_snapshot *snap); > > > + > > > > > > #endif > > >
diff --git a/drivers/gpu/drm/drm_exec.c b/drivers/gpu/drm/drm_exec.c index 1383680ffa4a..9eea5d0d3a98 100644 --- a/drivers/gpu/drm/drm_exec.c +++ b/drivers/gpu/drm/drm_exec.c @@ -57,6 +57,7 @@ static void drm_exec_unlock_all(struct drm_exec *exec) struct drm_gem_object *obj; unsigned long index; + WARN_ON(exec->snap); drm_exec_for_each_locked_object_reverse(exec, index, obj) { dma_resv_unlock(obj->resv); drm_gem_object_put(obj); @@ -90,6 +91,7 @@ void drm_exec_init(struct drm_exec *exec, u32 flags, unsigned nr) exec->num_objects = 0; exec->contended = DRM_EXEC_DUMMY; exec->prelocked = NULL; + exec->snap = NULL; } EXPORT_SYMBOL(drm_exec_init); @@ -301,7 +303,6 @@ int drm_exec_lock_obj(struct drm_exec *exec, struct drm_gem_object *obj) goto error_unlock; return 0; - error_unlock: dma_resv_unlock(obj->resv); return ret; @@ -395,5 +396,57 @@ int drm_exec_prepare_array(struct drm_exec *exec, } EXPORT_SYMBOL(drm_exec_prepare_array); +/** + * drm_exec_restore() - Restore the drm_exec state to the point of a snapshot. + * @exec: The drm_exec object with the state. + * @snap: The snapshot state. + * + * Restores the drm_exec object by means of unlocking and dropping references + * to objects locked after the snapshot. + */ +void drm_exec_restore(struct drm_exec *exec, struct drm_exec_snapshot *snap) +{ + struct drm_gem_object *obj; + unsigned int index; + + exec->snap = snap->saved_snap; + + drm_exec_for_each_locked_object_reverse(exec, index, obj) { + if (index + 1 == snap->num_locked) + break; + + dma_resv_unlock(obj->resv); + drm_gem_object_put(obj); + exec->objects[index] = NULL; + } + + exec->num_objects = snap->num_locked; + + if (!exec->prelocked) + exec->prelocked = snap->prelocked; + else + drm_gem_object_put(snap->prelocked); +} +EXPORT_SYMBOL(drm_exec_restore); + +/** + * drm_exec_snapshot() - Take a snapshot of the drm_exec state + * @exec: The drm_exec object with the state. + * @snap: The snapshot state. + * + * Records the @exec state in @snap. The @snap object is typically allocated + * in the stack of the caller. + */ +void drm_exec_snapshot(struct drm_exec *exec, struct drm_exec_snapshot *snap) +{ + snap->num_locked = exec->num_objects; + snap->prelocked = exec->prelocked; + if (snap->prelocked) + drm_gem_object_get(snap->prelocked); + snap->saved_snap = exec->snap; + exec->snap = snap; +} +EXPORT_SYMBOL(drm_exec_snapshot); + MODULE_DESCRIPTION("DRM execution context"); MODULE_LICENSE("Dual MIT/GPL"); diff --git a/include/drm/drm_exec.h b/include/drm/drm_exec.h index ea0f2117ee0c..0ce4d749511b 100644 --- a/include/drm/drm_exec.h +++ b/include/drm/drm_exec.h @@ -19,7 +19,6 @@ struct drm_exec { * @flags: Flags to control locking behavior */ u32 flags; - /** * @ticket: WW ticket used for acquiring locks */ @@ -49,6 +48,25 @@ struct drm_exec { * @prelocked: already locked GEM object due to contention */ struct drm_gem_object *prelocked; + + /** + * @snap: Pointer to the last snapshot taken or NULL if none. + */ + struct drm_exec_snapshot *snap; +}; + +/** + * struct drm_exec_snapshot - drm_exec snapshot information + */ +struct drm_exec_snapshot { + /** @saved_snap: Pointer to the previous snapshot or NULL. */ + struct drm_exec_snapshot *saved_snap; + + /** @prelocked: Refcounted pointer to the prelocked object at snapshot time. */ + struct drm_gem_object *prelocked; + + /** @num_locked: Number of locked objects at snapshot time. */ + unsigned long num_locked; }; int drm_exec_handle_contended(struct drm_exec *exec); @@ -160,5 +178,8 @@ int drm_exec_prepare_array(struct drm_exec *exec, struct drm_gem_object **objects, unsigned int num_objects, unsigned int num_fences); +void drm_exec_snapshot(struct drm_exec *exec, struct drm_exec_snapshot *snap); +void drm_exec_restore(struct drm_exec *exec, struct drm_exec_snapshot *snap); + #endif
When validating a buffer object for submission, we might need to lock a number of object for eviction to make room for the validation. This makes it pretty likely that validation will eventually succeed, since eventually the validating process will hold most dma_resv locks of the buffer objects residing in the memory type being validated for. However, once validation of a single object has succeeded it might not be beneficial to hold on to those locks anymore, and the validator would want to drop the locks of all objects taken during validation. Introduce a drm_exec snapshot functionality that can be used to record the locks held at a certain time, and a restore functionality that restores the drm_exec state to the snapshot by dropping all locks. Snapshots can be nested if needed. Cc: Christian König <christian.koenig@amd.com> Cc: Somalapuram Amaranath <Amaranath.Somalapuram@amd.com> Cc: Matthew Brost <matthew.brost@intel.com> Cc: <dri-devel@lists.freedesktop.org> Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com> --- drivers/gpu/drm/drm_exec.c | 55 +++++++++++++++++++++++++++++++++++++- include/drm/drm_exec.h | 23 +++++++++++++++- 2 files changed, 76 insertions(+), 2 deletions(-)