On 19/01/2021 16:20, Chris Wilson wrote:
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@xxxxxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Cc: Andi Shyti <andi.shyti@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # 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);
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Regards,
Tvrtko
