linux-kernel - Re: [PATCH] io_uring: use call_rcu

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Message-ID: <20221215184427.GI4001@paulmck-ThinkPad-P17-Gen-1>
Date:   Thu, 15 Dec 2022 10:44:27 -0800
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Dylan Yudaken <dylany@...a.com>
Cc:     Jens Axboe <axboe@...nel.dk>,
        Pavel Begunkov <asml.silence@...il.com>,
        io-uring@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...com, Joel Fernandes <joel@...lfernandes.org>
Subject: Re: [PATCH] io_uring: use call_rcu_hurry if signaling an eventfd

On Thu, Dec 15, 2022 at 10:41:38AM -0800, Dylan Yudaken wrote:
> io_uring uses call_rcu in the case it needs to signal an eventfd as a
> result of an eventfd signal, since recursing eventfd signals are not
> allowed. This should be calling the new call_rcu_hurry API to not delay
> the signal.
> 
> Signed-off-by: Dylan Yudaken <dylany@...a.com>
> 
> Cc: Joel Fernandes (Google) <joel@...lfernandes.org>
> Cc: Paul E. McKenney <paulmck@...nel.org>

Looks good!

Acked-by: Paul E. McKenney <paulmck@...nel.org>

> ---
>  io_uring/io_uring.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
> index b521186efa5c..2cb8c665bab1 100644
> --- a/io_uring/io_uring.c
> +++ b/io_uring/io_uring.c
> @@ -538,7 +538,7 @@ static void io_eventfd_signal(struct io_ring_ctx *ctx)
>  	} else {
>  		atomic_inc(&ev_fd->refs);
>  		if (!atomic_fetch_or(BIT(IO_EVENTFD_OP_SIGNAL_BIT), &ev_fd->ops))
> -			call_rcu(&ev_fd->rcu, io_eventfd_ops);
> +			call_rcu_hurry(&ev_fd->rcu, io_eventfd_ops);
>  		else
>  			atomic_dec(&ev_fd->refs);
>  	}
> 
> base-commit: 041fae9c105ae342a4245cf1e0dc56a23fbb9d3c
> -- 
> 2.30.2
>