Intel-GFX Archive on lore.kernel.org
 help / color / mirror / Atom feed
* [Intel-gfx] [PATCH] drm/i915/gt: Close race between enable_breadcrumbs and cancel_breadcrumbs
@ 2021-01-19 16:20 Chris Wilson
  2021-01-19 20:42 ` [Intel-gfx] ✗ Fi.CI.CHECKPATCH: warning for " Patchwork
                   ` (3 more replies)
  0 siblings, 4 replies; 5+ messages in thread
From: Chris Wilson @ 2021-01-19 16:20 UTC (permalink / raw)
  To: intel-gfx; +Cc: stable, Chris Wilson

If we enable_breadcrumbs for a request while that request is being
removed from HW; we may see that the request is active as we take the
ce->signal_lock and proceed to attach the request to ce->signals.
However, during unsubmission after marking the request as inactive, we
see that the request has not yet been added to ce->signals and so skip
the removal. Pull the check during cancel_breadcrumbs under the same
spinlock as enabling so that we the two tests are consistent in
enable/cancel.

Otherwise, we may insert a request onto ce->signal that we expect should
not be there:

  intel_context_remove_breadcrumbs:488 GEM_BUG_ON(!__i915_request_is_complete(rq))

While updating, we can note that we are always called with
irqs-disabled, due to the engine->active.lock being held at the single
caller, and so remove the irqsave/restore.

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/2931
Fixes: c18636f76344 ("drm/i915: Remove requirement for holding i915_request.lock for breadcrumbs")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Andi Shyti <andi.shyti@intel.com>
Cc: <stable@vger.kernel.org> # v5.10+
---
 drivers/gpu/drm/i915/gt/intel_breadcrumbs.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c b/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c
index d098fc0c14ec..34a645d6babd 100644
--- a/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c
+++ b/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c
@@ -453,16 +453,17 @@ void i915_request_cancel_breadcrumb(struct i915_request *rq)
 {
 	struct intel_breadcrumbs *b = READ_ONCE(rq->engine)->breadcrumbs;
 	struct intel_context *ce = rq->context;
-	unsigned long flags;
 	bool release;
 
-	if (!test_and_clear_bit(I915_FENCE_FLAG_SIGNAL, &rq->fence.flags))
+	spin_lock(&ce->signal_lock);
+	if (!test_and_clear_bit(I915_FENCE_FLAG_SIGNAL, &rq->fence.flags)) {
+		spin_unlock(&ce->signal_lock);
 		return;
+	}
 
-	spin_lock_irqsave(&ce->signal_lock, flags);
 	list_del_rcu(&rq->signal_link);
 	release = remove_signaling_context(b, ce);
-	spin_unlock_irqrestore(&ce->signal_lock, flags);
+	spin_unlock(&ce->signal_lock);
 	if (release)
 		intel_context_put(ce);
 
-- 
2.20.1

_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx

^ permalink raw reply related	[flat|nested] 5+ messages in thread
end of thread, other threads:[~2021-01-20  8:24 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2021-01-19 16:20 [Intel-gfx] [PATCH] drm/i915/gt: Close race between enable_breadcrumbs and cancel_breadcrumbs Chris Wilson
2021-01-19 20:42 ` [Intel-gfx] ✗ Fi.CI.CHECKPATCH: warning for " Patchwork
2021-01-19 21:11 ` [Intel-gfx] ✓ Fi.CI.BAT: success " Patchwork
2021-01-20  0:18 ` [Intel-gfx] ✗ Fi.CI.IGT: failure " Patchwork
2021-01-20  8:24 ` [Intel-gfx] [PATCH] " Tvrtko Ursulin

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox