linux-kernel - [PREEMPT_RT PATCH 1/3] i915: do not call lockdep_assert_irqs_disabled() on PREEMPT

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Date:   Mon, 19 Aug 2019 19:33:17 -0500
From:   Clark Williams <clark.williams@...il.com>
To:     bigeasy@...utronix.com
Cc:     tglx@...utronix.com, linux-rt-users@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PREEMPT_RT PATCH 1/3] i915: do not call lockdep_assert_irqs_disabled() on PREEMPT_RT

From: Clark Williams <williams@...hat.com>

The 'breadcrumb' code in the i915 driver calls lockdep_assert_irqs_disabled()
when starting some operations. This is valid on a stock kernel
but on a PREEMPT_RT kernel the spin_lock_irq*() calls to not disable
interrupts and likewise the spin_unlock_irq*() calls to not enable interrupts.

Conditionalize these calls based on whether PREEMPT_RT_FULL is enabled.

Signed-off-by: Clark Williams <williams@...hat.com>
---
 drivers/gpu/drm/i915/intel_breadcrumbs.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_breadcrumbs.c b/drivers/gpu/drm/i915/intel_breadcrumbs.c
index 832cb6b1e9bd..3eef6010ebf6 100644
--- a/drivers/gpu/drm/i915/intel_breadcrumbs.c
+++ b/drivers/gpu/drm/i915/intel_breadcrumbs.c
@@ -101,7 +101,8 @@ __dma_fence_signal__notify(struct dma_fence *fence)
 	struct dma_fence_cb *cur, *tmp;
 
 	lockdep_assert_held(fence->lock);
-	lockdep_assert_irqs_disabled();
+	if (!IS_ENABLED(CONFIG_PREEMPT_RT_FULL))
+		lockdep_assert_irqs_disabled();
 
 	list_for_each_entry_safe(cur, tmp, &fence->cb_list, node) {
 		INIT_LIST_HEAD(&cur->node);
@@ -276,7 +277,8 @@ void intel_engine_fini_breadcrumbs(struct intel_engine_cs *engine)
 bool i915_request_enable_breadcrumb(struct i915_request *rq)
 {
 	lockdep_assert_held(&rq->lock);
-	lockdep_assert_irqs_disabled();
+	if (!IS_ENABLED(CONFIG_PREEMPT_RT_FULL))
+		lockdep_assert_irqs_disabled();
 
 	if (test_bit(I915_FENCE_FLAG_ACTIVE, &rq->fence.flags)) {
 		struct intel_breadcrumbs *b = &rq->engine->breadcrumbs;
@@ -325,7 +327,8 @@ void i915_request_cancel_breadcrumb(struct i915_request *rq)
 	struct intel_breadcrumbs *b = &rq->engine->breadcrumbs;
 
 	lockdep_assert_held(&rq->lock);
-	lockdep_assert_irqs_disabled();
+	if (!IS_ENABLED(CONFIG_PREEMPT_RT_FULL))
+		lockdep_assert_irqs_disabled();
 
 	/*
 	 * We must wait for b->irq_lock so that we know the interrupt handler
-- 
2.21.0