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From: Changli Gao <xiaosuo@gmail.com>
Date: Wed, 28 Apr 2010 22:53:16 +0800
Message-ID: <v2x412e6f7f1004280753pd3438a3fv860edc580ecd6185@mail.gmail.com>
Subject: Re: [RFC] sched: implement the exclusive wait queue as a LIFO queue
To: David Howells <dhowells@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>, Alexander Viro <viro@zeniv.linux.org.uk>,
       Andrew Morton <akpm@linux-foundation.org>,
       "Eric W. Biederman" <ebiederm@xmission.com>,
       Davide Libenzi <davidel@xmailserver.org>,
       Roland Dreier <rolandd@cisco.com>,
       Stefan Richter <stefanr@s5r6.in-berlin.de>,
       Peter Zijlstra <a.p.zijlstra@chello.nl>,
       "David S. Miller" <davem@davemloft.net>,
       Eric Dumazet <dada1@cosmosbay.com>, Christoph Lameter <cl@linux.com>,
       Andreas Herrmann <andreas.herrmann3@amd.com>,
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On Wed, Apr 28, 2010 at 10:06 PM, David Howells <dhowells@redhat.com> wrote:
>
> I suspect you really want to have the semantics defined per-queue.  _Either_ a
> queue is FIFO (such as processes waiting for a resource so they can do
> something with it) _or_ it is LIFO (such as a pool of processes waiting to be
> given work).
>
> How often do the two actually mix?  And if they do, is that really an error?
>

The sock.sk_sleep is used by exclusive and non-exclusive wait queues.
exclusive and non-exclusive is identified by wait queues, not wait
queue heads. Maybe there is a historical reason. It is much like a
hack.

-- 
Regards，
Changli Gao(xiaosuo@gmail.com)
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