If we attempt to wake up a waiter, who is currently checking the seqno it will be in the TASK_INTERRUPTIBLE state and ttwu will report success. However, it is actually awake and functioning -- so delay reporting the actual wake up until it sleeps.
v2: Defend against !CONFIG_SMP v3: Don't filter out calls to wake_up_process References: https://bugs.freedesktop.org/show_bug.cgi?id=100007 Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk> Cc: Tvrtko Ursulin <tvrtko.ursu...@intel.com> Cc: Joonas Lahtinen <joonas.lahti...@linux.intel.com> --- drivers/gpu/drm/i915/intel_breadcrumbs.c | 18 ++++++++++++++++-- drivers/gpu/drm/i915/intel_ringbuffer.h | 4 ++++ 2 files changed, 20 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_breadcrumbs.c b/drivers/gpu/drm/i915/intel_breadcrumbs.c index 9ccbf26124c6..808d3a3cda0a 100644 --- a/drivers/gpu/drm/i915/intel_breadcrumbs.c +++ b/drivers/gpu/drm/i915/intel_breadcrumbs.c @@ -27,6 +27,12 @@ #include "i915_drv.h" +#ifdef CONFIG_SMP +#define task_asleep(tsk) (!(tsk)->on_cpu) +#else +#define task_asleep(tsk) ((tsk) != current) +#endif + static unsigned int __intel_breadcrumbs_wakeup(struct intel_breadcrumbs *b) { struct intel_wait *wait; @@ -37,8 +43,16 @@ static unsigned int __intel_breadcrumbs_wakeup(struct intel_breadcrumbs *b) wait = b->irq_wait; if (wait) { result = ENGINE_WAKEUP_WAITER; - if (wake_up_process(wait->tsk)) + + /* Be careful not to report a successful wakeup if the waiter + * is currently processing the seqno, where it will have + * already called set_task_state(TASK_INTERRUPTIBLE). + */ + if (task_asleep(wait->tsk)) result |= ENGINE_WAKEUP_ASLEEP; + + if (wake_up_process(wait->tsk)) + result |= ENGINE_WAKEUP_SUCCESS; } return result; @@ -98,7 +112,7 @@ static void intel_breadcrumbs_hangcheck(unsigned long data) * but we still have a waiter. Assuming all batches complete within * DRM_I915_HANGCHECK_JIFFIES [1.5s]! */ - if (intel_engine_wakeup(engine) & ENGINE_WAKEUP_ASLEEP) { + if (intel_engine_wakeup(engine) == ENGINE_WAKEUP) { missed_breadcrumb(engine); mod_timer(&engine->breadcrumbs.fake_irq, jiffies + 1); } else { diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h index 00d36aa4e26d..d25b88467e5e 100644 --- a/drivers/gpu/drm/i915/intel_ringbuffer.h +++ b/drivers/gpu/drm/i915/intel_ringbuffer.h @@ -668,6 +668,10 @@ static inline bool intel_engine_has_waiter(const struct intel_engine_cs *engine) unsigned int intel_engine_wakeup(struct intel_engine_cs *engine); #define ENGINE_WAKEUP_WAITER BIT(0) #define ENGINE_WAKEUP_ASLEEP BIT(1) +#define ENGINE_WAKEUP_SUCCESS BIT(2) +#define ENGINE_WAKEUP (ENGINE_WAKEUP_WAITER | \ + ENGINE_WAKEUP_ASLEEP | \ + ENGINE_WAKEUP_SUCCESS) void __intel_engine_disarm_breadcrumbs(struct intel_engine_cs *engine); void intel_engine_disarm_breadcrumbs(struct intel_engine_cs *engine); -- 2.11.0 _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx
