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drm/i915/breadcrumbs: Disable interrupt bottom-half first on idling

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Before walking the rbtree of waiters (marking them as complete and waking
them), decouple the interrupt handler. This prevents a race between the
missed waiter waking up and removing its intel_wait (which skips
checking the lock) and the interrupt handler dereferencing the
intel_wait. (Though we do not expect to encounter waiters during idle!)

Fixes: e1c0c91bda ("drm/i915: Wake up all waiters before idling")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170315210726.12095-3-chris@chris-wilson.co.uk
This commit is contained in:
Chris Wilson 2017-03-15 21:07:24 +00:00
parent 429732e860
commit a5cae7b8ed
1 changed files with 8 additions and 7 deletions
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15
drivers/gpu/drm/i915/intel_breadcrumbs.c
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@ -179,7 +179,7 @@ void __intel_engine_disarm_breadcrumbs(struct intel_engine_cs *engine)
void intel_engine_disarm_breadcrumbs(struct intel_engine_cs *engine) void intel_engine_disarm_breadcrumbs(struct intel_engine_cs *engine)
{ {
struct intel_breadcrumbs *b = &engine->breadcrumbs; struct intel_breadcrumbs *b = &engine->breadcrumbs;
struct intel_wait *wait, *n; struct intel_wait *wait, *n, *first;
if (!b->irq_armed) if (!b->irq_armed)
return; return;
@ -190,18 +190,19 @@ void intel_engine_disarm_breadcrumbs(struct intel_engine_cs *engine)
*/ */
spin_lock_irq(&b->rb_lock); spin_lock_irq(&b->rb_lock);
spin_lock(&b->irq_lock);
first = fetch_and_zero(&b->irq_wait);
__intel_engine_disarm_breadcrumbs(engine);
spin_unlock(&b->irq_lock);
rbtree_postorder_for_each_entry_safe(wait, n, &b->waiters, node) { rbtree_postorder_for_each_entry_safe(wait, n, &b->waiters, node) {
RB_CLEAR_NODE(&wait->node); RB_CLEAR_NODE(&wait->node);
if (wake_up_process(wait->tsk) && wait == b->irq_wait) if (wake_up_process(wait->tsk) && wait == first)
missed_breadcrumb(engine); missed_breadcrumb(engine);
} }
b->waiters = RB_ROOT; b->waiters = RB_ROOT;
spin_lock(&b->irq_lock);
b->irq_wait = NULL;
__intel_engine_disarm_breadcrumbs(engine);
spin_unlock(&b->irq_lock);
spin_unlock_irq(&b->rb_lock); spin_unlock_irq(&b->rb_lock);
} }