| Message ID | 20210816135139.10060-17-matthew.brost@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Clean up GuC CI failures, simplify locking, and kernel DOC | expand |
On Mon, Aug 16, 2021 at 06:51:33AM -0700, Matthew Brost wrote: > 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. > > Signed-off-by: Matthew Brost <matthew.brost@intel.com> Title should be "irq work", otherwise it reads a bit strange. Also these kind of nestings would be good to document in the kerneldoc too (maybe as you go even). -Daniel > --- > drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c | 15 ++++++++++++++- > drivers/gpu/drm/i915/i915_request.h | 5 +++++ > 2 files changed, 19 insertions(+), 1 deletion(-) > > 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 8c560ed14976..9ae4633aa7cb 100644 > --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c > +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c > @@ -2017,6 +2017,14 @@ 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; > @@ -2026,8 +2034,12 @@ static void __guc_signal_context_fence(struct intel_context *ce) > if (!list_empty(&ce->guc_state.fences)) > trace_intel_context_fence_release(ce); > > + /* > + * Use an IRQ to ensure locking order of sched_engine->lock -> > + * ce->guc_state.lock is preserved. > + */ > list_for_each_entry(rq, &ce->guc_state.fences, guc_fence_link) > - i915_sw_fence_complete(&rq->submit); > + irq_work_queue(&rq->submit_work); > > INIT_LIST_HEAD(&ce->guc_state.fences); > } > @@ -2137,6 +2149,7 @@ 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. > -- > 2.32.0 >
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 8c560ed14976..9ae4633aa7cb 100644 --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c @@ -2017,6 +2017,14 @@ 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; @@ -2026,8 +2034,12 @@ static void __guc_signal_context_fence(struct intel_context *ce) if (!list_empty(&ce->guc_state.fences)) trace_intel_context_fence_release(ce); + /* + * Use an IRQ to ensure locking order of sched_engine->lock -> + * ce->guc_state.lock is preserved. + */ list_for_each_entry(rq, &ce->guc_state.fences, guc_fence_link) - i915_sw_fence_complete(&rq->submit); + irq_work_queue(&rq->submit_work); INIT_LIST_HEAD(&ce->guc_state.fences); } @@ -2137,6 +2149,7 @@ 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.
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. Signed-off-by: Matthew Brost <matthew.brost@intel.com> --- drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c | 15 ++++++++++++++- drivers/gpu/drm/i915/i915_request.h | 5 +++++ 2 files changed, 19 insertions(+), 1 deletion(-)