> Paolo suggested to me on irc to call event_notifier_test_and_clear()
> after select() >0 from aio-win32.c's aio_prepare. Unfortunately, not all
> fds associated with ctx->notifiers are in AIO fd handlers set.
> (qemu_set_nonblock() in util/oslib-win32.c calls qemu_fd_register()).
That makes sense. Out of curiosity, what is a practical case of a socket
that is nonblocking but doesn't have an attached handler?
Another possibility (this one requires much more attention to avoid missing
some edge case; however, it should be easy to verify if it fixes the busy
loop) could be to move aio_notify_accept to just before setting ctx->notify_me.
This would work for both aio-posix and aio-win32.
Paolo
> Signed-off-by: Marc-André Lureau <marcandre.lur...@redhat.com>
> ---
> include/block/aio.h | 2 ++
> async.c | 6 ++++++
> 2 files changed, 8 insertions(+)
>
> diff --git a/include/block/aio.h b/include/block/aio.h
> index ca551e346f..a6da135bf3 100644
> --- a/include/block/aio.h
> +++ b/include/block/aio.h
> @@ -100,6 +100,7 @@ struct AioContext {
> */
> int walking_bh;
>
> +#ifndef _WIN32
> /* Used by aio_notify.
> *
> * "notified" is used to avoid expensive event_notifier_test_and_clear
> @@ -113,6 +114,7 @@ struct AioContext {
> * in the docs/aio_notify_accept.promela formal model.
> */
> bool notified;
> +#endif
> EventNotifier notifier;
>
> /* Thread pool for performing work and receiving completion callbacks */
> diff --git a/async.c b/async.c
> index b2de360c23..8c2a68b6cc 100644
> --- a/async.c
> +++ b/async.c
> @@ -329,15 +329,21 @@ void aio_notify(AioContext *ctx)
> smp_mb();
> if (ctx->notify_me) {
> event_notifier_set(&ctx->notifier);
> +#ifndef _WIN32
> atomic_mb_set(&ctx->notified, true);
> +#endif
> }
> }
>
> void aio_notify_accept(AioContext *ctx)
> {
> +#ifndef _WIN32
> if (atomic_xchg(&ctx->notified, false)) {
> +#endif
> event_notifier_test_and_clear(&ctx->notifier);
> +#ifndef _WIN32
> }
> +#endif
> }
>
> static void aio_timerlist_notify(void *opaque)
> --
> 2.11.0
>
>
