From 6ef98ea0dacd8bee62d6823b1dea80269137c240 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Fri, 17 Feb 2017 15:13:03 +0000 Subject: [PATCH] drm/i915: Only start with the fake-irq timer if interrupts are dead As a backup to waiting on a user-interrupt from the GPU, we use a heavy and frequent timer to wake up the waiting process should we detect an inconsistency whilst waiting. After seeing a "missed interrupt", the next time we wait, we restart the heavy timer. This patch is more reluctant to restart the timer and will only do so if we have not see any interrupts since when we started the fake irq timer. If we are seeing interrupts, then the waiters are being woken normally and we had an incoherency that caused to miss last time - that is unlikely to reoccur and so taking the risk of stalling again seems pragmatic. Signed-off-by: Chris Wilson Cc: Tvrtko Ursulin Cc: Mika Kuoppala Reviewed-by: Tvrtko Ursulin Link: http://patchwork.freedesktop.org/patch/msgid/20170217151304.16665-5-chris@chris-wilson.co.uk --- drivers/gpu/drm/i915/intel_breadcrumbs.c | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_breadcrumbs.c b/drivers/gpu/drm/i915/intel_breadcrumbs.c index f78b9baf61b6..5932e2dc0c6f 100644 --- a/drivers/gpu/drm/i915/intel_breadcrumbs.c +++ b/drivers/gpu/drm/i915/intel_breadcrumbs.c @@ -107,6 +107,23 @@ static void irq_disable(struct intel_engine_cs *engine) spin_unlock(&engine->i915->irq_lock); } +static bool use_fake_irq(const struct intel_breadcrumbs *b) +{ + const struct intel_engine_cs *engine = + container_of(b, struct intel_engine_cs, breadcrumbs); + + if (!test_bit(engine->id, &engine->i915->gpu_error.missed_irq_rings)) + return false; + + /* Only start with the heavy weight fake irq timer if we have not + * seen any interrupts since enabling it the first time. If the + * interrupts are still arriving, it means we made a mistake in our + * engine->seqno_barrier(), a timing error that should be transient + * and unlikely to reoccur. + */ + return atomic_read(&engine->irq_count) == b->hangcheck_interrupts; +} + static void __intel_breadcrumbs_enable_irq(struct intel_breadcrumbs *b) { struct intel_engine_cs *engine = @@ -144,8 +161,7 @@ static void __intel_breadcrumbs_enable_irq(struct intel_breadcrumbs *b) b->irq_enabled = true; } - if (!b->irq_enabled || - test_bit(engine->id, &i915->gpu_error.missed_irq_rings)) { + if (!b->irq_enabled || use_fake_irq(b)) { mod_timer(&b->fake_irq, jiffies + 1); i915_queue_hangcheck(i915); } else {