Subject: [PATCH 05/10] drm/i915: Don't check for atomic context on PREEMPT_RT
From: Sebastian Andrzej Siewior <[email-masked]>
Date: Mon, 25 Oct 2021 15:05:18 +0200

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. Therefore I'm
currently unsure about changing this.

Link: https://lore.kernel.org/all/[email-masked]/
Signed-off-by: Sebastian Andrzej Siewior <[email-masked]>
---
 drivers/gpu/drm/i915/i915_utils.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/gpu/drm/i915/i915_utils.h
+++ b/drivers/gpu/drm/i915/i915_utils.h
@@ -343,7 +343,7 @@ wait_remaining_ms_from_jiffies(unsigned
 #define wait_for(COND, MS)		_wait_for((COND), (MS) * 1000, 10, 1000)
 
 /* If CONFIG_PREEMPT_COUNT is disabled, in_atomic() always reports false. */
-#if defined(CONFIG_DRM_I915_DEBUG) && defined(CONFIG_PREEMPT_COUNT)
+#if defined(CONFIG_DRM_I915_DEBUG) && defined(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)