[PATCH 1/6] drm/i915: Drop racy markup of missed-irqs from idle-worker

[Chris Wilson]

During the idle-worker we disable the hangcheck and so kick any waiters
that should have been completed (since the GPU is now idle). Unlike the
hangcheck, we do not take any care to avoid the race between the irq
handler and ourselves, and so it is possible for us to declare a missed
interrupt even as the bottom-half is being scheduled to run. Let's
ignore this race to stop a potential false-positive error.

References: https://bugs.freedesktop.org/show_bug.cgi?id=96974
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com>
---
 drivers/gpu/drm/i915/i915_gem.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 40047eb48826..c8436639b3ed 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2705,11 +2705,14 @@ i915_gem_idle_work_handler(struct work_struct *work)
 	dev_priv->gt.awake = false;
 	rearm_hangcheck = false;
 
+	/* As we have disabled hangcheck, we need to unstick any waiters still
+	 * hanging around. However, as we may be racing against the interrupt
+	 * handler or the waiters themselves, we skip enabling the fake-irq.
+	 */
 	stuck_engines = intel_kick_waiters(dev_priv);
-	if (unlikely(stuck_engines)) {
-		DRM_DEBUG_DRIVER("kicked stuck waiters...missed irq\n");
-		dev_priv->gpu_error.missed_irq_rings |= stuck_engines;
-	}
+	if (unlikely(stuck_engines))
+		DRM_DEBUG_DRIVER("kicked stuck waiters (%x)...missed irq?\n",
+				 stuck_engines);
 
 	if (INTEL_GEN(dev_priv) >= 6)
 		gen6_rps_idle(dev_priv);
-- 
2.8.1