diff options
| author | Chris Wilson <chris@chris-wilson.co.uk> | 2016-07-06 12:39:01 +0100 |
|---|---|---|
| committer | Chris Wilson <chris@chris-wilson.co.uk> | 2016-07-06 12:47:31 +0100 |
| commit | 99fe4a5f7383559ee120492124365e708a587130 (patch) | |
| tree | c031429c25386b3a991ba2197db3779c59da6b06 | |
| parent | 04171313cb25311acf82279284d722fed7b70d53 (diff) | |
drm/i915: Wake up the bottom-half if we steal their interrupt
Following on from the scenario Tvrtko envisioned to explain a hard-to-hit
race with multiple first waiters, we could also then race in the
__i915_request_irq_complete() and the bottom-half may miss the vital
irq-seqno barrier and so go to sleep not noticing their seqno is
complete.
v2: unlock, not double lock the rcu_read_lock.
Fixes: 3d5564e91025 ("drm/i915: Only apply one barrier after...")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1467805142-22219-2-git-send-email-chris@chris-wilson.co.uk
| -rw-r--r-- | drivers/gpu/drm/i915/i915_drv.h | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h index c269e0ad4057..11e9769411e9 100644 --- a/drivers/gpu/drm/i915/i915_drv.h +++ b/drivers/gpu/drm/i915/i915_drv.h @@ -3998,7 +3998,10 @@ static inline bool __i915_request_irq_complete(struct drm_i915_gem_request *req) * is woken. */ if (engine->irq_seqno_barrier && + READ_ONCE(engine->breadcrumbs.tasklet) == current && cmpxchg_relaxed(&engine->irq_posted, 1, 0)) { + struct task_struct *tsk; + /* The ordering of irq_posted versus applying the barrier * is crucial. The clearing of the current irq_posted must * be visible before we perform the barrier operation, @@ -4012,6 +4015,25 @@ static inline bool __i915_request_irq_complete(struct drm_i915_gem_request *req) * seqno update. */ engine->irq_seqno_barrier(engine); + + /* If we consume the irq, but we are no longer the bottom-half, + * the real bottom-half may not have serialised their own + * seqno check with the irq-barrier (i.e. may have inspected + * the seqno before we believe it coherent since they see + * irq_posted == false but we are still running). + */ + rcu_read_lock(); + tsk = READ_ONCE(engine->breadcrumbs.tasklet); + if (tsk && tsk != current) + /* Note that if the bottom-half is changed as we + * are sending the wake-up, the new bottom-half will + * be woken by whomever made the change. We only have + * to worry about when we steal the irq-posted for + * ourself. + */ + wake_up_process(tsk); + rcu_read_unlock(); + if (i915_gem_request_completed(req)) return true; } |