Commit b0d83888 authored by Matthew Brost's avatar Matthew Brost Committed by John Harrison
Browse files

drm/i915/guc: Release submit fence from an irq_work 



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: default avatarDaniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: default avatarMatthew Brost <matthew.brost@intel.com>
Signed-off-by: default avatarJohn Harrison <John.C.Harrison@Intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210909164744.31249-16-matthew.brost@intel.com
parent ae36b629

drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c

+19 −3
Original line number Diff line number Diff line
@@ -2049,17 +2049,32 @@ 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);

}
@@ -2169,6 +2184,7 @@ 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);

drivers/gpu/drm/i915/i915_request.h

+5 −0
Original line number Diff line number Diff line
@@ -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.