drm/gem: Add ww_acquire_ctx support to drm_gem_lru_scan()

If the callback is going to have to attempt to grab more locks, it is
useful to have an ww_acquire_ctx to avoid locking order problems.

Why not use the drm_exec helper instead?  Mainly because (a) where
ww_acquire_init() is called is awkward, and (b) we don't really
need to retry after backoff, we can just move on to the next object.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Signed-off-by: Rob Clark <robin.clark@oss.qualcomm.com>
Tested-by: Antonino Maniscalco <antomani103@gmail.com>
Reviewed-by: Antonino Maniscalco <antomani103@gmail.com>
Patchwork: https://patchwork.freedesktop.org/patch/661463/

diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
index 19d50d254fe691b6be129a1061cc8f05786a58d7..0905ef6786e9688956d3e69d84c2737d92fd3d59 100644 (file)
--- a/drivers/gpu/drm/drm_gem.c
+++ b/drivers/gpu/drm/drm_gem.c
@@ -1429,12 +1429,14 @@ EXPORT_SYMBOL(drm_gem_lru_move_tail);
  * @nr_to_scan: The number of pages to try to reclaim
  * @remaining: The number of pages left to reclaim, should be initialized by caller
  * @shrink: Callback to try to shrink/reclaim the object.
+ * @ticket: Optional ww_acquire_ctx context to use for locking
  */
 unsigned long
 drm_gem_lru_scan(struct drm_gem_lru *lru,
                 unsigned int nr_to_scan,
                 unsigned long *remaining,
-                bool (*shrink)(struct drm_gem_object *obj))
+                bool (*shrink)(struct drm_gem_object *obj, struct ww_acquire_ctx *ticket),
+                struct ww_acquire_ctx *ticket)
 {
        struct drm_gem_lru still_in_lru;
        struct drm_gem_object *obj;
@@ -1467,17 +1469,20 @@ drm_gem_lru_scan(struct drm_gem_lru *lru,
                 */
                mutex_unlock(lru->lock);
 
+               if (ticket)
+                       ww_acquire_init(ticket, &reservation_ww_class);
+
                /*
                 * Note that this still needs to be trylock, since we can
                 * hit shrinker in response to trying to get backing pages
                 * for this obj (ie. while it's lock is already held)
                 */
-               if (!dma_resv_trylock(obj->resv)) {
+               if (!ww_mutex_trylock(&obj->resv->lock, ticket)) {
                        *remaining += obj->size >> PAGE_SHIFT;
                        goto tail;
                }
 
-               if (shrink(obj)) {
+               if (shrink(obj, ticket)) {
                        freed += obj->size >> PAGE_SHIFT;
 
                        /*
@@ -1491,6 +1496,9 @@ drm_gem_lru_scan(struct drm_gem_lru *lru,
 
                dma_resv_unlock(obj->resv);
 
+               if (ticket)
+                       ww_acquire_fini(ticket);
+
 tail:
                drm_gem_object_put(obj);
                mutex_lock(lru->lock);

diff --git a/drivers/gpu/drm/msm/msm_gem_shrinker.c b/drivers/gpu/drm/msm/msm_gem_shrinker.c
index 07ca4ddfe4e37348e69b95deeb5771f75c9d1bb8..de185fc3408479b76a3210de2ac655e5b4b99120 100644 (file)
--- a/drivers/gpu/drm/msm/msm_gem_shrinker.c
+++ b/drivers/gpu/drm/msm/msm_gem_shrinker.c
@@ -44,7 +44,7 @@ msm_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc)
 }
 
 static bool
-purge(struct drm_gem_object *obj)
+purge(struct drm_gem_object *obj, struct ww_acquire_ctx *ticket)
 {
        if (!is_purgeable(to_msm_bo(obj)))
                return false;
@@ -58,7 +58,7 @@ purge(struct drm_gem_object *obj)
 }
 
 static bool
-evict(struct drm_gem_object *obj)
+evict(struct drm_gem_object *obj, struct ww_acquire_ctx *ticket)
 {
        if (is_unevictable(to_msm_bo(obj)))
                return false;
@@ -79,21 +79,21 @@ wait_for_idle(struct drm_gem_object *obj)
 }
 
 static bool
-active_purge(struct drm_gem_object *obj)
+active_purge(struct drm_gem_object *obj, struct ww_acquire_ctx *ticket)
 {
        if (!wait_for_idle(obj))
                return false;
 
-       return purge(obj);
+       return purge(obj, ticket);
 }
 
 static bool
-active_evict(struct drm_gem_object *obj)
+active_evict(struct drm_gem_object *obj, struct ww_acquire_ctx *ticket)
 {
        if (!wait_for_idle(obj))
                return false;
 
-       return evict(obj);
+       return evict(obj, ticket);
 }
 
 static unsigned long
@@ -102,7 +102,7 @@ msm_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)
        struct msm_drm_private *priv = shrinker->private_data;
        struct {
                struct drm_gem_lru *lru;
-               bool (*shrink)(struct drm_gem_object *obj);
+               bool (*shrink)(struct drm_gem_object *obj, struct ww_acquire_ctx *ticket);
                bool cond;
                unsigned long freed;
                unsigned long remaining;
@@ -122,8 +122,9 @@ msm_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)
                        continue;
                stages[i].freed =
                        drm_gem_lru_scan(stages[i].lru, nr,
-                                       &stages[i].remaining,
-                                        stages[i].shrink);
+                                        &stages[i].remaining,
+                                        stages[i].shrink,
+                                        NULL);
                nr -= stages[i].freed;
                freed += stages[i].freed;
                remaining += stages[i].remaining;
@@ -164,7 +165,7 @@ msm_gem_shrinker_shrink(struct drm_device *dev, unsigned long nr_to_scan)
 static const int vmap_shrink_limit = 15;
 
 static bool
-vmap_shrink(struct drm_gem_object *obj)
+vmap_shrink(struct drm_gem_object *obj, struct ww_acquire_ctx *ticket)
 {
        if (!is_vunmapable(to_msm_bo(obj)))
                return false;
@@ -192,7 +193,8 @@ msm_gem_shrinker_vmap(struct notifier_block *nb, unsigned long event, void *ptr)
                unmapped += drm_gem_lru_scan(lrus[idx],
                                             vmap_shrink_limit - unmapped,
                                             &remaining,
-                                            vmap_shrink);
+                                            vmap_shrink,
+                                            NULL);
        }
 
        *(unsigned long *)ptr += unmapped;

diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
index 1a79ec3fe45c940d91d790f9ff42e5519f1e909c..d3a7b43e2c637b164eba5af7cc2fc8ef09d4f0a4 100644 (file)
--- a/include/drm/drm_gem.h
+++ b/include/drm/drm_gem.h
@@ -560,10 +560,12 @@ void drm_gem_lru_init(struct drm_gem_lru *lru, struct mutex *lock);
 void drm_gem_lru_remove(struct drm_gem_object *obj);
 void drm_gem_lru_move_tail_locked(struct drm_gem_lru *lru, struct drm_gem_object *obj);
 void drm_gem_lru_move_tail(struct drm_gem_lru *lru, struct drm_gem_object *obj);
-unsigned long drm_gem_lru_scan(struct drm_gem_lru *lru,
-                              unsigned int nr_to_scan,
-                              unsigned long *remaining,
-                              bool (*shrink)(struct drm_gem_object *obj));
+unsigned long
+drm_gem_lru_scan(struct drm_gem_lru *lru,
+                unsigned int nr_to_scan,
+                unsigned long *remaining,
+                bool (*shrink)(struct drm_gem_object *obj, struct ww_acquire_ctx *ticket),
+                struct ww_acquire_ctx *ticket);
 
 int drm_gem_evict_locked(struct drm_gem_object *obj);