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Commit 27745e82 authored by Chris Wilson's avatar Chris Wilson
Browse files

drm/i915/execlists: Use a local lock for dfs_link access 



Avoid requiring struct_mutex for exclusive access to the temporary
dfs_link inside the i915_dependency as not all callers may want to touch
struct_mutex. So rather than force them to take a highly contended
lock, introduce a local lock for the execlists schedule operation.

Reported-by: default avatarDavid Weinehall <david.weinehall@linux.intel.com>
Fixes: 9a151987 ("drm/i915: Add execution priority boosting for mmioflips")
Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: David Weinehall <david.weinehall@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161116152721.11053-1-chris@chris-wilson.co.uk


Reviewed-by: default avatarTvrtko Ursulin <tvrtko.ursulin@intel.com>
parent 85ee17eb

drivers/gpu/drm/i915/intel_lrc.c

+5 −2
Original line number Diff line number Diff line
@@ -694,6 +694,7 @@ pt_lock_engine(struct i915_priotree *pt, struct intel_engine_cs *locked) 


static void execlists_schedule(struct drm_i915_gem_request *request, int prio)

{

	static DEFINE_MUTEX(lock);

	struct intel_engine_cs *engine = NULL;

	struct i915_dependency *dep, *p;

	struct i915_dependency stack;
@@ -702,8 +703,8 @@ static void execlists_schedule(struct drm_i915_gem_request *request, int prio) 
	if (prio <= READ_ONCE(request->priotree.priority))

		return;



	/* Need BKL in order to use the temporary link inside i915_dependency */

	lockdep_assert_held(&request->i915->drm.struct_mutex);

	/* Need global lock to use the temporary link inside i915_dependency */

	mutex_lock(&lock);



	stack.signaler = &request->priotree;

	list_add(&stack.dfs_link, &dfs);
@@ -770,6 +771,8 @@ static void execlists_schedule(struct drm_i915_gem_request *request, int prio) 
	if (engine)

		spin_unlock_irq(&engine->timeline->lock);



	mutex_unlock(&lock);



	/* XXX Do we need to preempt to make room for us and our deps? */

}