On 29/11/2019 11:28, Chris Wilson wrote:
Quoting Tvrtko Ursulin (2019-11-29 11:15:46)
On 29/11/2019 09:39, Chris Wilson wrote:
As the i915_active.retire() may be running on another CPU as we detect
that the i915_active is idle, we may not wait for the retirement itself.
Wait for the remote callback by waiting for the retirement worker.
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=112424
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/i915_active.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/drivers/gpu/drm/i915/i915_active.c b/drivers/gpu/drm/i915/i915_active.c
index 479195ecbc6c..e8630ee33336 100644
--- a/drivers/gpu/drm/i915/i915_active.c
+++ b/drivers/gpu/drm/i915/i915_active.c
@@ -469,6 +469,7 @@ int i915_active_wait(struct i915_active *ref)
if (wait_var_event_interruptible(ref, i915_active_is_idle(ref)))
return -EINTR;
+ flush_work(&ref->work);
return 0;
}
Hm, but wake_up_war is in the worker so how does wait_var_event wake the
waiter up before it has been retired?
Remember the wait_event pattern is to skip the wait if COND is already
met. So since the first thing the retirement does is the
atomic_dec_and_test(), we can see ref->count == 0 very early, long
before ref->retire() is called. Our selftest is checking that if
i915_active_wait() reports completion, the callback has also run and
that the i915_active can then be destroyed.
True!
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Regards,
Tvrtko
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