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drm/i915: Don't check for atomic context on PREEMPT_RT

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The !in_atomic() check in _wait_for_atomic() triggers on PREEMPT_RT
because the uncore::lock is a spinlock_t and does not disable
preemption or interrupts.

Changing the uncore:lock to a raw_spinlock_t doubles the worst case
latency on an otherwise idle testbox during testing.

Ignore _WAIT_FOR_ATOMIC_CHECK() on PREEMPT_RT.

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Link: https://lore.kernel.org/all/20211006164628.s2mtsdd2jdbfyf7g@linutronix.de/
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/20250714153954.629393-4-bigeasy@linutronix.de
Signed-off-by: Maarten Lankhorst <dev@lankhorst.se>
This commit is contained in:
Sebastian Andrzej Siewior
2025-07-14 17:39:48 +02:00
committed by Maarten Lankhorst
parent bba9aa4165
commit 8a643df55f
1 changed files with 7 additions and 2 deletions
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9
drivers/gpu/drm/i915/i915_utils.h
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@@ -267,8 +267,13 @@ wait_remaining_ms_from_jiffies(unsigned long timestamp_jiffies, int to_wait_ms)
(Wmax))
#define wait_for(COND, MS) _wait_for((COND), (MS) * 1000, 10, 1000)
/* If CONFIG_PREEMPT_COUNT is disabled, in_atomic() always reports false. */
#if IS_ENABLED(CONFIG_DRM_I915_DEBUG) && IS_ENABLED(CONFIG_PREEMPT_COUNT)
/*
* If CONFIG_PREEMPT_COUNT is disabled, in_atomic() always reports false.
* On PREEMPT_RT the context isn't becoming atomic because it is used in an
* interrupt handler or because a spinlock_t is acquired. This leads to
* warnings which don't occur otherwise and therefore the check is disabled.
*/
#if IS_ENABLED(CONFIG_DRM_I915_DEBUG) && IS_ENABLED(CONFIG_PREEMPT_COUNT) && !defined(CONFIG_PREEMPT_RT)
# define _WAIT_FOR_ATOMIC_CHECK(ATOMIC) WARN_ON_ONCE((ATOMIC) && !in_atomic())
#else
# define _WAIT_FOR_ATOMIC_CHECK(ATOMIC) do { } while (0)