From: Chris Wilson chris@chris-wilson.co.uk
commit e4747cb3ec3c232d65c84cbe77633abd5871fda3 upstream.
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->signals 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 making it symmetric to enable_breadcrumbs.
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+ Reviewed-by: Tvrtko Ursulin tvrtko.ursulin@intel.com Link: https://patchwork.freedesktop.org/patch/msgid/20210119162057.31097-1-chris@c... (cherry picked from commit e7004ea4f5f528f5a5018f0b70cab36d25315498) Signed-off-by: Jani Nikula jani.nikula@intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/gpu/drm/i915/gt/intel_breadcrumbs.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
--- a/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c +++ b/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c @@ -451,10 +451,12 @@ void i915_request_cancel_breadcrumb(stru struct intel_context *ce = rq->context; 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(&ce->signal_lock); list_del_rcu(&rq->signal_link); release = remove_signaling_context(rq->engine->breadcrumbs, ce); spin_unlock(&ce->signal_lock);