linux-kernel - Re: [patch] epoll-fix-compiler-warning-and-optimize-the-non-blocking-path-fix

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Date:	Wed, 26 Jan 2011 07:05:07 -0800 (PST)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	Johannes Weiner <hannes@...xchg.org>
cc:	Andrew Morton <akpm@...ux-foundation.org>, shawn.bohrer@...il.com,
	linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
	mm-commits@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [patch]
 epoll-fix-compiler-warning-and-optimize-the-non-blocking-path-fix

On Wed, 26 Jan 2011, Johannes Weiner wrote:

> The non-blocking ep_poll path optimization introduced skipping over
> the return value setup.
> 
> Initialize it properly, my userspace gets upset by epoll_wait()
> returning random things.
> 
> In addition, remove the reinitialization at the fetch_events label,
> the return value is garuanteed to be zero when execution reaches
> there.
> 
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>
> Cc: Shawn Bohrer <shawn.bohrer@...il.com>
> Cc: Davide Libenzi <davidel@...ilserver.org>

Thank you for posting it. Obvious ACK.



> ---
>  fs/eventpoll.c |    3 +--
>  1 files changed, 1 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/eventpoll.c b/fs/eventpoll.c
> index f7cb6cb..afe4238 100644
> --- a/fs/eventpoll.c
> +++ b/fs/eventpoll.c
> @@ -1147,7 +1147,7 @@ static int ep_send_events(struct eventpoll *ep,
>  static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
>  		   int maxevents, long timeout)
>  {
> -	int res, eavail, timed_out = 0;
> +	int res = 0, eavail, timed_out = 0;
>  	unsigned long flags;
>  	long slack = 0;
>  	wait_queue_t wait;
> @@ -1173,7 +1173,6 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
>  fetch_events:
>  	spin_lock_irqsave(&ep->lock, flags);
>  
> -	res = 0;
>  	if (!ep_events_available(ep)) {
>  		/*
>  		 * We don't have any available event to return to the caller.
> -- 
> 1.7.3.5
> 
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