Re: [PATCH] eventfd: guard wake_up in eventfd fs calls as well

[Jens Axboe <axboe@kernel.dk>]

On 8/16/22 07:59, Dylan Yudaken wrote:
> Guard wakeups that the user can trigger, and that may end up triggering a
> call back into eventfd_signal. This is in addition to the current approach
> that only guards in eventfd_signal.
> 
> Rename in_eventfd_signal -> in_eventfd at the same time to reflect this.
> 
> Without this there would be a deadlock in the following code using libaio:
> 
> int main()
> {
> 	struct io_context *ctx = NULL;
> 	struct iocb iocb;
> 	struct iocb *iocbs[] = { &iocb };
> 	int evfd;
>         uint64_t val = 1;
> 
> 	evfd = eventfd(0, EFD_CLOEXEC);
> 	assert(!io_setup(2, &ctx));
> 	io_prep_poll(&iocb, evfd, POLLIN);
> 	io_set_eventfd(&iocb, evfd);
> 	assert(1 == io_submit(ctx, 1, iocbs));
>         write(evfd, &val, 8);
> }

Reviewed-by: Jens Axboe <axboe@kernel.dk>

-- 
Jens Axboe