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Date: Sun, 29 Oct 2000 08:11:23 +0100
From: Andi Kleen <ak@suse.de>
To: Rik van Riel <riel@conectiva.com.br>
Cc: davem@redhat.com, linux-kernel@vger.kernel.org,
        netdev <netdev@oss.sgi.com>
Subject: Re: tcp.c::wait_for_tcp_memory() buggy ?
Message-ID: <20001029081123.A18126@gruyere.muc.suse.de>
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In-Reply-To: <Pine.LNX.4.21.0010290122050.4224-100000@duckman.distro.conectiva>; from riel@conectiva.com.br on Sun, Oct 29, 2000 at 01:28:38AM -0200
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On Sun, Oct 29, 2000 at 01:28:38AM -0200, Rik van Riel wrote:
> Except for doing a test on tcp_memory_free(sk), where we
> do NOT hold the lock we're so dutifully clinging to during
> the rest of the loop...

And rechecking it later while holding the loop on the next iteration.

Also usually the caller also does a check again and iterates as needed.

> 
> As I said, I can't put my finger down on what exactly is
> wrong, but this code looks subtle enough that, together
> with the bugreport I got (on IRC), I have the feeling that
> it just _can't_ be right ...

With the right setup of multiple threads writing all the time
on a single socket you could probably starve one, making it loop forever here.
(it does not try to be fair) 



-Andi

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