From 34730fed9fd54e893ec0177c97a509de3ee0a5a4 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Sat, 20 Aug 2016 15:54:08 +0100 Subject: [PATCH] drm/i915: Ignore stuck requests when considering hangs If the engine isn't being retired (worker starvation?) then it is possible for us to repeatedly observe that between consecutive hangchecks the seqno on the ring to be the same and there remain unretired requests. Ignore these completely and only regard the engine as busy for the purpose of hang detection (not stall detection) if there are outstanding breadcrumbs. In recent history we have looked at using both the request and seqno as indication of activity on the engine, but that was reduced to just inspecting seqno in commit cffa781e5907 ("drm/i915: Simplify check for idleness in hangcheck"). However, in commit dcff85c8443e ("drm/i915: Enable i915_gem_wait_for_idle() without holding struct_mutex"), I made the decision to use the new common lockless function, under the assumption that request retirement was more frequent than hangcheck and so we would not have a stuck busy check. The flaw there was in forgetting that we accumulate the hang score, and so successive checks seeing a stuck request, albeit with the GPU advancing elsewhere and so not necessary the same stuck request, would eventually trigger the hang. Fixes: dcff85c8443e ("drm/i915: Enable i915_gem_wait_for_idle()...") Signed-off-by: Chris Wilson Cc: Mika Kuoppala Link: http://patchwork.freedesktop.org/patch/msgid/20160820145408.32180-1-chris@chris-wilson.co.uk Reviewed-by: Mika Kuoppala --- drivers/gpu/drm/i915/i915_irq.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c index ebb83d5a448b..7610eca4f687 100644 --- a/drivers/gpu/drm/i915/i915_irq.c +++ b/drivers/gpu/drm/i915/i915_irq.c @@ -3079,6 +3079,7 @@ static void i915_hangcheck_elapsed(struct work_struct *work) bool busy = intel_engine_has_waiter(engine); u64 acthd; u32 seqno; + u32 submit; semaphore_clear_deadlocks(dev_priv); @@ -3094,9 +3095,10 @@ static void i915_hangcheck_elapsed(struct work_struct *work) acthd = intel_engine_get_active_head(engine); seqno = intel_engine_get_seqno(engine); + submit = READ_ONCE(engine->last_submitted_seqno); if (engine->hangcheck.seqno == seqno) { - if (!intel_engine_is_active(engine)) { + if (i915_seqno_passed(seqno, submit)) { engine->hangcheck.action = HANGCHECK_IDLE; if (busy) { /* Safeguard against driver failure */