From 4be173813e57c7298103a83155c2391b5b167b4c Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Fri, 6 Jun 2014 10:22:29 +0100 Subject: [PATCH] drm/i915: Reorder semaphore deadlock check If a semaphore is waiting on another ring, which in turn happens to be waiting on the first ring, but that second semaphore has been signalled, we will be able to kick the second ring and so can treat the first ring as a valid WAIT and not as HUNG. v2: Be paranoid and cap the potential recursion depth whilst visiting the semaphore signallers. (Mika) References: https://bugs.freedesktop.org/show_bug.cgi?id=54226 References: https://bugs.freedesktop.org/show_bug.cgi?id=75502 Signed-off-by: Chris Wilson Cc: Mika Kuoppala Cc: stable@vger.kernel.org Reviewed-by: Mika Kuoppala Signed-off-by: Jani Nikula --- drivers/gpu/drm/i915/i915_irq.c | 18 ++++++++++++++---- drivers/gpu/drm/i915/intel_ringbuffer.h | 2 +- 2 files changed, 15 insertions(+), 5 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c index cf288a95347c..69aaa1100986 100644 --- a/drivers/gpu/drm/i915/i915_irq.c +++ b/drivers/gpu/drm/i915/i915_irq.c @@ -2847,10 +2847,14 @@ static int semaphore_passed(struct intel_engine_cs *ring) struct intel_engine_cs *signaller; u32 seqno, ctl; - ring->hangcheck.deadlock = true; + ring->hangcheck.deadlock++; signaller = semaphore_waits_for(ring, &seqno); - if (signaller == NULL || signaller->hangcheck.deadlock) + if (signaller == NULL) + return -1; + + /* Prevent pathological recursion due to driver bugs */ + if (signaller->hangcheck.deadlock >= I915_NUM_RINGS) return -1; /* cursory check for an unkickable deadlock */ @@ -2858,7 +2862,13 @@ static int semaphore_passed(struct intel_engine_cs *ring) if (ctl & RING_WAIT_SEMAPHORE && semaphore_passed(signaller) < 0) return -1; - return i915_seqno_passed(signaller->get_seqno(signaller, false), seqno); + if (i915_seqno_passed(signaller->get_seqno(signaller, false), seqno)) + return 1; + + if (signaller->hangcheck.deadlock) + return -1; + + return 0; } static void semaphore_clear_deadlocks(struct drm_i915_private *dev_priv) @@ -2867,7 +2877,7 @@ static void semaphore_clear_deadlocks(struct drm_i915_private *dev_priv) int i; for_each_ring(ring, dev_priv, i) - ring->hangcheck.deadlock = false; + ring->hangcheck.deadlock = 0; } static enum intel_ring_hangcheck_action diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h index 910c83cf7d44..e72017bdcd7f 100644 --- a/drivers/gpu/drm/i915/intel_ringbuffer.h +++ b/drivers/gpu/drm/i915/intel_ringbuffer.h @@ -55,7 +55,7 @@ struct intel_ring_hangcheck { u32 seqno; int score; enum intel_ring_hangcheck_action action; - bool deadlock; + int deadlock; }; struct intel_ringbuffer {