[PATCH v4 22/23] drm/msm: Drop struct_mutex in shrinker path

Rob Clark
2020-10-23T16:51:35Z

Now that the inactive_list is protected by mm_lock, and everything
else on per-obj basis is protected by obj->lock, we no longer depend
on struct_mutex.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Kristian H. Kristensen <hoegsberg@google.com>
---
drivers/gpu/drm/msm/msm_gem.c | 1 -
drivers/gpu/drm/msm/msm_gem_shrinker.c | 54 --------------------------
2 files changed, 55 deletions(-)

diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c
index 7f24a58c0390..a9a834bb7794 100644
--- a/drivers/gpu/drm/msm/msm_gem.c
+++ b/drivers/gpu/drm/msm/msm_gem.c
@@ -688,7 +688,6 @@ void msm_gem_purge(struct drm_gem_object *obj)
struct drm_device *dev = obj->dev;
struct msm_gem_object *msm_obj = to_msm_bo(obj);

- WARN_ON(!mutex_is_locked(&dev->struct_mutex));
WARN_ON(!is_purgeable(msm_obj));
WARN_ON(obj->import_attach);

diff --git a/drivers/gpu/drm/msm/msm_gem_shrinker.c b/drivers/gpu/drm/msm/msm_gem_shrinker.c
index 6be073b8ca08..6f4b1355725f 100644
--- a/drivers/gpu/drm/msm/msm_gem_shrinker.c
+++ b/drivers/gpu/drm/msm/msm_gem_shrinker.c
@@ -8,48 +8,13 @@
#include "msm_gem.h"
#include "msm_gpu_trace.h"

-static bool msm_gem_shrinker_lock(struct drm_device *dev, bool *unlock)
-{
- /* NOTE: we are *closer* to being able to get rid of
- * mutex_trylock_recursive().. the msm_gem code itself does
- * not need struct_mutex, although codepaths that can trigger
- * shrinker are still called in code-paths that hold the
- * struct_mutex.
- *
- * Also, msm_obj->madv is protected by struct_mutex.
- *
- * The next step is probably split out a seperate lock for
- * protecting inactive_list, so that shrinker does not need
- * struct_mutex.
- */
- switch (mutex_trylock_recursive(&dev->struct_mutex)) {
- case MUTEX_TRYLOCK_FAILED:
- return false;
-
- case MUTEX_TRYLOCK_SUCCESS:
- *unlock = true;
- return true;
-
- case MUTEX_TRYLOCK_RECURSIVE:
- *unlock = false;
- return true;
- }
-
- BUG();
-}
-
static unsigned long
msm_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc)
{
struct msm_drm_private *priv =
container_of(shrinker, struct msm_drm_private, shrinker);
- struct drm_device *dev = priv->dev;
struct msm_gem_object *msm_obj;
unsigned long count = 0;
- bool unlock;
-
- if (!msm_gem_shrinker_lock(dev, &unlock))
- return 0;

mutex_lock(&priv->mm_lock);

@@ -63,9 +28,6 @@ msm_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc)

mutex_unlock(&priv->mm_lock);

- if (unlock)
- mutex_unlock(&dev->struct_mutex);
-
return count;
}

@@ -74,13 +36,8 @@ msm_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)
{
struct msm_drm_private *priv =
container_of(shrinker, struct msm_drm_private, shrinker);
- struct drm_device *dev = priv->dev;
struct msm_gem_object *msm_obj;
unsigned long freed = 0;
- bool unlock;
-
- if (!msm_gem_shrinker_lock(dev, &unlock))
- return SHRINK_STOP;

mutex_lock(&priv->mm_lock);

@@ -98,9 +55,6 @@ msm_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)

mutex_unlock(&priv->mm_lock);

- if (unlock)
- mutex_unlock(&dev->struct_mutex);
-
if (freed > 0)
trace_msm_gem_purge(freed << PAGE_SHIFT);

@@ -112,13 +66,8 @@ msm_gem_shrinker_vmap(struct notifier_block *nb, unsigned long event, void *ptr)
{
struct msm_drm_private *priv =
container_of(nb, struct msm_drm_private, vmap_notifier);
- struct drm_device *dev = priv->dev;
struct msm_gem_object *msm_obj;
unsigned unmapped = 0;
- bool unlock;
-
- if (!msm_gem_shrinker_lock(dev, &unlock))
- return NOTIFY_DONE;

mutex_lock(&priv->mm_lock);

@@ -141,9 +90,6 @@ msm_gem_shrinker_vmap(struct notifier_block *nb, unsigned long event, void *ptr)

mutex_unlock(&priv->mm_lock);

- if (unlock)
- mutex_unlock(&dev->struct_mutex);
-
*(unsigned long *)ptr += unmapped;

if (unmapped > 0)
--
2.26.2