On 15/03/2017 18:32, Chris Wilson wrote:
On Wed, Mar 15, 2017 at 06:20:16PM +0000, Tvrtko Ursulin wrote:
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?
I wanted to associate it with b->irq_lock, that was my thinking.
b->rb_lock also sadly has to be irqsafe.
That makes sense yes.
__intel_breadcrumbs_next() also serves remove_wait, did you mean to
remove the assert there as well?
Yes, I was thinking only one would do it.
We can safely ignore this patch, it should be catered by lockdep fairly
well, I was just being paranoid and going through the possible causes
and documenting my progress.
This also makes sense. I think it's the best option.
Regards,
Tvrtko
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