Re: [PATCH 2/6] drm/i915/breadcrumbs: Assert that irqs are disabled as we update the bottom-half

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On 15/03/2017 14:01, Chris Wilson wrote:
Check that we have disabled irqs before we take the spin_lock around
reassigned the breadcrumbs.irq_wait.

Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
---
 drivers/gpu/drm/i915/intel_breadcrumbs.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_breadcrumbs.c b/drivers/gpu/drm/i915/intel_breadcrumbs.c
index 3f222dee4c25..35529b35a276 100644
--- a/drivers/gpu/drm/i915/intel_breadcrumbs.c
+++ b/drivers/gpu/drm/i915/intel_breadcrumbs.c
@@ -301,8 +301,11 @@ static inline void __intel_breadcrumbs_next(struct intel_engine_cs *engine,
 {
 	struct intel_breadcrumbs *b = &engine->breadcrumbs;

+	GEM_BUG_ON(!irqs_disabled());
+
 	spin_lock(&b->irq_lock);
 	GEM_BUG_ON(!b->irq_armed);
+	GEM_BUG_ON(!b->irq_wait);
 	b->irq_wait = to_wait(next);
 	spin_unlock(&b->irq_lock);

@@ -395,8 +398,10 @@ static bool __intel_engine_add_wait(struct intel_engine_cs *engine,
 	}

 	if (first) {
-		spin_lock(&b->irq_lock);
 		GEM_BUG_ON(rb_first(&b->waiters) != &wait->node);
+		GEM_BUG_ON(!irqs_disabled());
+
+		spin_lock(&b->irq_lock);
 		b->irq_wait = wait;
 		/* After assigning ourselves as the new bottom-half, we must
 		 * perform a cursory check to prevent a missed interrupt.


A single GEM_BUG_ON(!irqs_disabled()) at the top of __intel_engine_add_wait might be more logical?

As a weakly related side note, there is a stale comment mentioning b->lock in intel_engine_enable_signalling.

Regards,

Tvrtko
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