[Intel-gfx] [PATCH] drm/i915/gt: Do not add same i915_request to intel_context twice

[dong . yang]

From: "Yang, Dong" <dong.y...@intel.com>

With unknow race condition, the i915_request will be added
to intel_context list twice, and result in system panic.

If node alreay exist then do not add it again.

Signed-off-by: Yang, Dong <dong.y...@intel.com>
---
 drivers/gpu/drm/i915/gt/intel_breadcrumbs.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c 
b/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c
index 209cf265bf74..9c7bc060d2ae 100644
--- a/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c
+++ b/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c
@@ -387,6 +387,9 @@ static void insert_breadcrumb(struct i915_request *rq)
                }
        }
 
+       if (&rq->signal_link == pos)
+               return;
+
        i915_request_get(rq);
        list_add_rcu(&rq->signal_link, pos);
        GEM_BUG_ON(!check_signal_order(ce, rq));
-- 
2.27.0