40 lines
1.8 KiB
Diff
40 lines
1.8 KiB
Diff
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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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Date: Mon, 25 Oct 2021 15:05:18 +0200
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Subject: [PATCH 3/8] drm/i915: Don't check for atomic context on PREEMPT_RT
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.11/older/patches-6.11-rt7.tar.xz
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The !in_atomic() check in _wait_for_atomic() triggers on PREEMPT_RT
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because the uncore::lock is a spinlock_t and does not disable
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preemption or interrupts.
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Changing the uncore:lock to a raw_spinlock_t doubles the worst case
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latency on an otherwise idle testbox during testing.
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Ignore _WAIT_FOR_ATOMIC_CHECK() on PREEMPT_RT.
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Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
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Link: https://lore.kernel.org/all/20211006164628.s2mtsdd2jdbfyf7g@linutronix.de/
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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drivers/gpu/drm/i915/i915_utils.h | 9 +++++++--
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1 file changed, 7 insertions(+), 2 deletions(-)
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--- a/drivers/gpu/drm/i915/i915_utils.h
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+++ b/drivers/gpu/drm/i915/i915_utils.h
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@@ -273,8 +273,13 @@ wait_remaining_ms_from_jiffies(unsigned
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(Wmax))
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#define wait_for(COND, MS) _wait_for((COND), (MS) * 1000, 10, 1000)
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-/* If CONFIG_PREEMPT_COUNT is disabled, in_atomic() always reports false. */
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-#if defined(CONFIG_DRM_I915_DEBUG) && defined(CONFIG_PREEMPT_COUNT)
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+/*
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+ * If CONFIG_PREEMPT_COUNT is disabled, in_atomic() always reports false.
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+ * On PREEMPT_RT the context isn't becoming atomic because it is used in an
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+ * interrupt handler or because a spinlock_t is acquired. This leads to
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+ * warnings which don't occur otherwise and therefore the check is disabled.
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+ */
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+#if defined(CONFIG_DRM_I915_DEBUG) && defined(CONFIG_PREEMPT_COUNT) && !defined(CONFIG_PREEMPT_RT)
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# define _WAIT_FOR_ATOMIC_CHECK(ATOMIC) WARN_ON_ONCE((ATOMIC) && !in_atomic())
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#else
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# define _WAIT_FOR_ATOMIC_CHECK(ATOMIC) do { } while (0)
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