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@xxxxxxxxx>
---
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 9a53bae367b1..deb2e821e441 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
@@ -2025,6 +2025,14 @@ 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;
@@ -2034,8 +2042,12 @@ 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);
}
@@ -2145,6 +2157,7 @@ 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
