[PATCH v2 2/3] drm/i915: Update the breadcrumb interrupt counter before enabling

Chris Wilson
2016-07-21T06:57:49Z

In order to close a race with a long running hangcheck comparing a stale
interrupt counter with a just started waiter, we need to first bump the
counter as we start the fresh wait.

References: https://bugs.freedesktop.org/show_bug.cgi?id=96974
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
---
drivers/gpu/drm/i915/intel_breadcrumbs.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_breadcrumbs.c b/drivers/gpu/drm/i915/intel_breadcrumbs.c
index f0b56e3f4abe..d893ccdd62ac 100644
--- a/drivers/gpu/drm/i915/intel_breadcrumbs.c
+++ b/drivers/gpu/drm/i915/intel_breadcrumbs.c
@@ -51,6 +51,13 @@ static void irq_enable(struct intel_engine_cs *engine)
*/
engine->breadcrumbs.irq_posted = true;

+ /* Make sure the current hangcheck doesn't falsely accuse a just
+ * started irq handler from missing an interrupt (because the
+ * interrupt count still matches the stale value from when
+ * the irq handler was disabled, many hangchecks ago).
+ */
+ engine->breadcrumbs.irq_wakeups++;
+
spin_lock_irq(&engine->i915->irq_lock);
engine->irq_enable(engine);
spin_unlock_irq(&engine->i915->irq_lock);
--
2.8.1