[PATCH] drm/i915/gt: Ensure irqs' status does not change with spin_unlock

[Krzysztof Karas]

spin_unlock() function enables irqs regardless of their state
before spin_lock() was called. This might result in an interrupt
while holding a lock further down in the execution, as seen in
GitLab issue #13399.

Try to remedy the problem by saving irq state before spin lock
acquisition.

Signed-off-by: Krzysztof Karas <krzysztof.karas at intel.com>
---
This issue is hit rarely on CI and I was not able to reproduce
it locally. There might be more places where we should save and
restore irq state, so I am not adding "Closes" label for the
issue yet.

 drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

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 12f1ba7ca9c1..e9102f7246f5 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
@@ -4338,10 +4338,11 @@ static void guc_bump_inflight_request_prio(struct i915_request *rq,
 static void guc_retire_inflight_request_prio(struct i915_request *rq)
 {
 	struct intel_context *ce = request_to_scheduling_context(rq);
+	unsigned long flags;
 
-	spin_lock(&ce->guc_state.lock);
+	spin_lock_irqsave(&ce->guc_state.lock, flags);
 	guc_prio_fini(rq, ce);
-	spin_unlock(&ce->guc_state.lock);
+	spin_unlock_irqrestore(&ce->guc_state.lock, flags);
 }
 
 static void sanitize_hwsp(struct intel_engine_cs *engine)
-- 
2.34.1