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: David Weinehall <david.weinehall@xxxxxxxxxxxxxxx>
Fixes: 9a151987d709 ("drm/i915: Add execution priority boosting for mmioflips")
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Cc: David Weinehall <david.weinehall@xxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/intel_lrc.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index e23b6a2600fb..10e59ff0d8f1 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -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? */
}
--
2.10.2
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