[Mesa-dev] [PATCH] os: Check for spurious wakeups in pipe_barrier_wait.

[Brian Paul]

Vinson Lee wrote:
> I would like this to be reviewed before it is committed.
> 
> The current implementation and this patch doesn't address the potential 
> existing case where count is erroneously initialized with zero.
> That can be a separate patch.

Do you mean add assert(count > 0) in pipe_barrier_init() or something 
else?


> os: Check for spurious wakeups in pipe_barrier_wait.
> 
> Add a 64-bit counter that is incremented whenever the barrier becomes full. A woken thread
> checks the counter. If the counter has not changed then it has been
> spuriously woken and goes back to sleep. If the counter has changed then it was properly
> signaled and exits the barrier.

I'm not sure I understand the problem.

Can you give an example of how we'd get a spurious wake-up signal?

-Brian