[SRU][R][Unstable][PATCH 09/12] UBUNTU: SAUCE: drm/i915: Consider RCU read section as atomic.

[Kevin Becker]

From: Sebastian Andrzej Siewior <bigeasy at linutronix.de>

BugLink: https://bugs.launchpad.net/bugs/2143181

Locking and/ or running inside interrupt handler will not lead to an
atomic section on PREEMPT_RT. The RCU read section needs to be
considered because all locks, which become sleeping locks on
PREEMPT_RT, start a RCU read section. Scheduling/ sleeping while within
a RCU read section is invalid.

Check for also for RCU read section in stop_timeout() to determine if it
is safe to sleep.

Reviewed-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
Link: https://lore.kernel.org/r/20250714153954.629393-9-bigeasy@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior <bigeasy at linutronix.de>
Signed-off-by: Kevin Becker <kevin.becker at canonical.com>
---
 drivers/gpu/drm/i915/gt/intel_engine_cs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
index d37966ec7a92..ecf52a530417 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
@@ -1607,7 +1607,7 @@ u64 intel_engine_get_last_batch_head(const struct intel_engine_cs *engine)
 
 static unsigned long stop_timeout(const struct intel_engine_cs *engine)
 {
-	if (in_atomic() || irqs_disabled()) /* inside atomic preempt-reset? */
+	if (in_atomic() || irqs_disabled() || rcu_preempt_depth()) /* inside atomic preempt-reset? */
 		return 0;
 
 	/*
-- 
2.43.0