From: Matthew Brost matthew.brost@intel.com
A subsequent patch will flip the locking hierarchy from ce->guc_state.lock -> sched_engine->lock to sched_engine->lock -> ce->guc_state.lock. As such we need to release the submit fence for a request from an IRQ to break a lock inversion - i.e. the fence must be release went holding ce->guc_state.lock and the releasing of the can acquire sched_engine->lock.
v2: (Daniele) - Delete request from list before calling irq_work_queue
Reviewed-by: Daniele Ceraolo Spurio daniele.ceraolospurio@intel.com Signed-off-by: Matthew Brost matthew.brost@intel.com --- .../gpu/drm/i915/gt/uc/intel_guc_submission.c | 22 ++++++++++++++++--- drivers/gpu/drm/i915/i915_request.h | 5 +++++ 2 files changed, 24 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c index 8509e827a8d0..7c7cbd57d568 100644 --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c @@ -2035,17 +2035,32 @@ static const struct intel_context_ops guc_context_ops = { .create_virtual = guc_create_virtual, };
+static void submit_work_cb(struct irq_work *wrk) +{ + struct i915_request *rq = container_of(wrk, typeof(*rq), submit_work); + + might_lock(&rq->engine->sched_engine->lock); + i915_sw_fence_complete(&rq->submit); +} + static void __guc_signal_context_fence(struct intel_context *ce) { - struct i915_request *rq; + struct i915_request *rq, *rn;
lockdep_assert_held(&ce->guc_state.lock);
if (!list_empty(&ce->guc_state.fences)) trace_intel_context_fence_release(ce);
- list_for_each_entry(rq, &ce->guc_state.fences, guc_fence_link) - i915_sw_fence_complete(&rq->submit); + /* + * Use an IRQ to ensure locking order of sched_engine->lock -> + * ce->guc_state.lock is preserved. + */ + list_for_each_entry_safe(rq, rn, &ce->guc_state.fences, + guc_fence_link) { + list_del(&rq->guc_fence_link); + irq_work_queue(&rq->submit_work); + }
INIT_LIST_HEAD(&ce->guc_state.fences); } @@ -2155,6 +2170,7 @@ static int guc_request_alloc(struct i915_request *rq) spin_lock_irqsave(&ce->guc_state.lock, flags); if (context_wait_for_deregister_to_register(ce) || context_pending_disable(ce)) { + init_irq_work(&rq->submit_work, submit_work_cb); i915_sw_fence_await(&rq->submit);
list_add_tail(&rq->guc_fence_link, &ce->guc_state.fences); diff --git a/drivers/gpu/drm/i915/i915_request.h b/drivers/gpu/drm/i915/i915_request.h index 1bc1349ba3c2..d818cfbfc41d 100644 --- a/drivers/gpu/drm/i915/i915_request.h +++ b/drivers/gpu/drm/i915/i915_request.h @@ -218,6 +218,11 @@ struct i915_request { }; struct llist_head execute_cb; struct i915_sw_fence semaphore; + /** + * @submit_work: complete submit fence from an IRQ if needed for + * locking hierarchy reasons. + */ + struct irq_work submit_work;
/* * A list of everyone we wait upon, and everyone who waits upon us.