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Commit 00c26cf9 authored by Chris Wilson's avatar Chris Wilson
Browse files

drm/i915: Remove toplevel struct_mutex locking from debugfs/i915_drop_caches 



I have a plan to write a quick test to exercise concurrent usage of
i915_gem_shrink(), the simplest way looks to be to have multiple threads
using debugfs/i915_drop_caches. However, we currently take one lock over
the entire function, serialising the calls into i915_gem_shrink() so
reduce the lock coverage.

Testcase: igt/gem_shrink/reclaim
Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170524162653.5446-1-chris@chris-wilson.co.uk


Reviewed-by: default avatarJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
parent b5a82425

drivers/gpu/drm/i915/i915_debugfs.c

+14 −16
Original line number Diff line number Diff line
@@ -4289,27 +4289,28 @@ i915_drop_caches_set(void *data, u64 val) 
{

	struct drm_i915_private *dev_priv = data;

	struct drm_device *dev = &dev_priv->drm;

	int ret;

	int ret = 0;



	DRM_DEBUG("Dropping caches: 0x%08llx\n", val);



	/* No need to check and wait for gpu resets, only libdrm auto-restarts

	 * on ioctls on -EAGAIN. */

	if (val & (DROP_ACTIVE | DROP_RETIRE)) {

		ret = mutex_lock_interruptible(&dev->struct_mutex);

		if (ret)

			return ret;



	if (val & DROP_ACTIVE) {

		if (val & DROP_ACTIVE)

			ret = i915_gem_wait_for_idle(dev_priv,

						     I915_WAIT_INTERRUPTIBLE |

						     I915_WAIT_LOCKED);

		if (ret)

			goto unlock;

	}



		if (val & DROP_RETIRE)

			i915_gem_retire_requests(dev_priv);



		mutex_unlock(&dev->struct_mutex);

	}



	lockdep_set_current_reclaim_state(GFP_KERNEL);

	if (val & DROP_BOUND)

		i915_gem_shrink(dev_priv, LONG_MAX, I915_SHRINK_BOUND);
@@ -4321,9 +4322,6 @@ i915_drop_caches_set(void *data, u64 val) 
		i915_gem_shrink_all(dev_priv);

	lockdep_clear_current_reclaim_state();



unlock:

	mutex_unlock(&dev->struct_mutex);



	if (val & DROP_FREED) {

		synchronize_rcu();

		i915_gem_drain_freed_objects(dev_priv);