drm/msm/gem: Move locking in shrinker path

Move grabbing the bo lock into shrinker, with a msm_gem_trylock() to
skip over bo's that are already locked.  This gets rid of the nested
lock classes.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Kristian H. Kristensen <hoegsberg@google.com>
Signed-off-by: Rob Clark <robdclark@chromium.org>

1 files changed, 11 insertions, 18 deletions

diff --git a/drivers/gpu/drm/msm/msm_gem.h b/drivers/gpu/drm/msm/msm_gem.h
index d55d5401a2d2..766ce278c74a 100644
--- a/drivers/gpu/drm/msm/msm_gem.h
+++ b/drivers/gpu/drm/msm/msm_gem.h
@@ -162,6 +162,13 @@ msm_gem_lock(struct drm_gem_object *obj)
 	mutex_lock(&msm_obj->lock);
 }
 
+static inline bool __must_check
+msm_gem_trylock(struct drm_gem_object *obj)
+{
+	struct msm_gem_object *msm_obj = to_msm_bo(obj);
+	return mutex_trylock(&msm_obj->lock) == 1;
+}
+
 static inline int
 msm_gem_lock_interruptible(struct drm_gem_object *obj)
 {
@@ -190,6 +197,7 @@ static inline bool is_active(struct msm_gem_object *msm_obj)
 
 static inline bool is_purgeable(struct msm_gem_object *msm_obj)
 {
+	WARN_ON(!msm_gem_is_locked(&msm_obj->base));
 	WARN_ON(!mutex_is_locked(&msm_obj->base.dev->struct_mutex));
 	return (msm_obj->madv == MSM_MADV_DONTNEED) && msm_obj->sgt &&
 			!msm_obj->base.dma_buf && !msm_obj->base.import_attach;
@@ -197,27 +205,12 @@ static inline bool is_purgeable(struct msm_gem_object *msm_obj)
 
 static inline bool is_vunmapable(struct msm_gem_object *msm_obj)
 {
+	WARN_ON(!msm_gem_is_locked(&msm_obj->base));
 	return (msm_obj->vmap_count == 0) && msm_obj->vaddr;
 }
 
-/* The shrinker can be triggered while we hold objA->lock, and need
- * to grab objB->lock to purge it.  Lockdep just sees these as a single
- * class of lock, so we use subclasses to teach it the difference.
- *
- * OBJ_LOCK_NORMAL is implicit (ie. normal mutex_lock() call), and
- * OBJ_LOCK_SHRINKER is used by shrinker.
- *
- * It is *essential* that we never go down paths that could trigger the
- * shrinker for a purgable object.  This is ensured by checking that
- * msm_obj->madv == MSM_MADV_WILLNEED.
- */
-enum msm_gem_lock {
-	OBJ_LOCK_NORMAL,
-	OBJ_LOCK_SHRINKER,
-};
-
-void msm_gem_purge(struct drm_gem_object *obj, enum msm_gem_lock subclass);
-void msm_gem_vunmap(struct drm_gem_object *obj, enum msm_gem_lock subclass);
+void msm_gem_purge(struct drm_gem_object *obj);
+void msm_gem_vunmap(struct drm_gem_object *obj);
 void msm_gem_free_work(struct work_struct *work);
 
 /* Created per submit-ioctl, to track bo's and cmdstream bufs, etc,