[PATCH 3/4] ntdll: Implement thread-ID alerts using futexes if possible.

[Paul Gofman]

On 11/17/21 06:50, Zebediah Figura wrote:
> +        while (!InterlockedExchange( futex, 0 ))
> +        {
> +            if (timeout)
> +            {
> +                LONGLONG timeleft = update_timeout( end );
> +                struct timespec timespec;
> +
> +                timespec.tv_sec = timeleft / (ULONGLONG)TICKSPERSEC;
> +                timespec.tv_nsec = (timeleft % TICKSPERSEC) * 100;
> +                ret = futex_wait( futex, 0, &timespec );
> +            }
> +            else
> +                ret = futex_wait( futex, 0, NULL );
> +
> +            if (ret == -1 && errno == ETIMEDOUT) return STATUS_TIMEOUT;
> +        }
> +        return STATUS_ALERTED;
> +    }
> +#endif
> +
Do you think it is possible or makes sense to handle EINTR and retry 
wait to avoid delivering spurious wakeups to the application in this 
case? We have a lot of SIGUSR1 for Wine async I/O handling. Also, maybe 
it would be interesting to log unexpected errors? Not that anything 
besides EINTR should ever happen as I understand, but sometimes 
unexpected errors happen and may indicate a real issue and that happened 
once in the past with the current upstream in process sync.