[Intel-gfx] [PATCH 3/4] drm/i915: Refactor common lock handling between shrinker count/scan

[Chris Wilson]

We can share a few lines of tricky lock handling we need to use for both
shrinker routines and in the process fix the return value for count()
when reporting a deadlock.

Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_gem.c | 42 +++++++++++++++++++++--------------------
 1 file changed, 22 insertions(+), 20 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 219fe35f9c45..135ee8bd55f6 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -4913,6 +4913,22 @@ static bool mutex_is_locked_by(struct mutex *mutex, 
struct task_struct *task)
 #endif
 }
 
+static bool i915_gem_shrinker_lock(struct drm_device *dev, bool *unlock)
+{
+       if (!mutex_trylock(&dev->struct_mutex)) {
+               if (!mutex_is_locked_by(&dev->struct_mutex, current))
+                       return false;
+
+               if (to_i915(dev)->mm.shrinker_no_lock_stealing)
+                       return false;
+
+               *unlock = false;
+       } else
+               *unlock = true;
+
+       return true;
+}
+
 static int num_vma_bound(struct drm_i915_gem_object *obj)
 {
        struct i915_vma *vma;
@@ -4932,18 +4948,11 @@ i915_gem_shrinker_count(struct shrinker *shrinker, 
struct shrink_control *sc)
                container_of(shrinker, struct drm_i915_private, mm.shrinker);
        struct drm_device *dev = dev_priv->dev;
        struct drm_i915_gem_object *obj;
-       bool unlock = true;
        unsigned long count;
+       bool unlock;
 
-       if (!mutex_trylock(&dev->struct_mutex)) {
-               if (!mutex_is_locked_by(&dev->struct_mutex, current))
-                       return 0;
-
-               if (dev_priv->mm.shrinker_no_lock_stealing)
-                       return 0;
-
-               unlock = false;
-       }
+       if (!i915_gem_shrinker_lock(dev, &unlock))
+               return 0;
 
        count = 0;
        list_for_each_entry(obj, &dev_priv->mm.unbound_list, global_list)
@@ -5031,17 +5040,10 @@ i915_gem_shrinker_scan(struct shrinker *shrinker, 
struct shrink_control *sc)
                container_of(shrinker, struct drm_i915_private, mm.shrinker);
        struct drm_device *dev = dev_priv->dev;
        unsigned long freed;
-       bool unlock = true;
+       bool unlock;
 
-       if (!mutex_trylock(&dev->struct_mutex)) {
-               if (!mutex_is_locked_by(&dev->struct_mutex, current))
-                       return SHRINK_STOP;
-
-               if (dev_priv->mm.shrinker_no_lock_stealing)
-                       return SHRINK_STOP;
-
-               unlock = false;
-       }
+       if (!i915_gem_shrinker_lock(dev, &unlock))
+               return SHRINK_STOP;
 
        freed = i915_gem_purge(dev_priv, sc->nr_to_scan);
        if (freed < sc->nr_to_scan)
-- 
1.9.1

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