linux-kernel - Re: [patch 1/2] fix epoll single pass code and add wait-exclusive flag ...

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Message-Id: <20070513122950.e30f2c80.akpm@linux-foundation.org>
Date:	Sun, 13 May 2007 12:29:50 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Davide Libenzi <davidel@...ilserver.org>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [patch 1/2] fix epoll single pass code and add wait-exclusive
 flag ...

On Fri, 11 May 2007 19:30:31 -0700 Davide Libenzi <davidel@...ilserver.org> wrote:

> Fixes the epoll single pass code. During the unlocked event delivery
> (to userspace) code, the poll callback can re-issue new events, and
> we must receive them correctly. Since we loop in a lockless fashion,
> we want to be O(nready), and we don't want to flash on/off the spinlock
> for every event, we have the poll callback to use a secondary list to
> queue events while we're inside the event delivery loop.
> The rw_semaphore has been turned into a mutex.
> This patch also adds the wait-exclusive flag, as suggested by Davi Arnaut.
> 
> ...
> @@ -534,6 +547,8 @@
>  	}
>  
>  	mutex_unlock(&epmutex);
> +
> +	mutex_destroy(&ep->mtx);
>  }

It's a little alarming to see a dereference of `ep' right at the end of a
function called ep_free(ep).

Code is OK, but perhaps the kfree(ep) should be moved into ep_free()?

I'm a bit stunned at the size of these two patches.
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