drm/i915: Do an unlocked wait before set-cache-level ioctl

Since a change in cache level is likely to trigger an unbind, avoid
waiting under the mutex by preemptively doing an unlocked wait.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/20170119082211.21257-1-chris@chris-wilson.co.uk
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index b2f8ac1386a28fe7ea684c3abcae2957ac7e2585..4f23a8f4303e1adfbe4163f7d89da36f8f61eec4 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3397,7 +3397,7 @@ int i915_gem_set_caching_ioctl(struct drm_device *dev, void *data,
        struct drm_i915_gem_caching *args = data;
        struct drm_i915_gem_object *obj;
        enum i915_cache_level level;
-       int ret;
+       int ret = 0;
 
        switch (args->caching) {
        case I915_CACHING_NONE:
@@ -3422,20 +3422,29 @@ int i915_gem_set_caching_ioctl(struct drm_device *dev, void *data,
                return -EINVAL;
        }
 
-       ret = i915_mutex_lock_interruptible(dev);
+       obj = i915_gem_object_lookup(file, args->handle);
+       if (!obj)
+               return -ENOENT;
+
+       if (obj->cache_level == level)
+               goto out;
+
+       ret = i915_gem_object_wait(obj,
+                                  I915_WAIT_INTERRUPTIBLE,
+                                  MAX_SCHEDULE_TIMEOUT,
+                                  to_rps_client(file));
        if (ret)
-               return ret;
+               goto out;
 
-       obj = i915_gem_object_lookup(file, args->handle);
-       if (!obj) {
-               ret = -ENOENT;
-               goto unlock;
-       }
+       ret = i915_mutex_lock_interruptible(dev);
+       if (ret)
+               goto out;
 
        ret = i915_gem_object_set_cache_level(obj, level);
-       i915_gem_object_put(obj);
-unlock:
        mutex_unlock(&dev->struct_mutex);
+
+out:
+       i915_gem_object_put(obj);
        return ret;
 }