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From: David Howells <dhowells@redhat.com>
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References: <20090424172845.GB13026@redhat.com> <20090413181733.GA10424@redhat.com> <32260.1239658818@redhat.com> <20090413214852.GA1127@redhat.com> <1239659841.16771.26.camel@heimdal.trondhjem.org> <20090413222451.GA2758@redhat.com> <14561.1239873018@redhat.com> <21239.1240407420@redhat.com> <5591.1240417398@redhat.com> <21209.1240504344@redhat.com> <26028.1240573601@redhat.com> 
To: Oleg Nesterov <oleg@redhat.com>
Cc: dhowells@redhat.com, Ingo Molnar <mingo@elte.hu>, torvalds@osdl.org,
       Andrew Morton <akpm@linux-foundation.org>, serue@us.ibm.com,
       viro@zeniv.linux.org.uk,
       "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
       Nick Piggin <nickpiggin@yahoo.com.au>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] It may not be assumed that wake_up(), finish_wait() and co. imply a memory barrier
Date: Fri, 24 Apr 2009 18:53:45 +0100
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Oleg Nesterov <oleg@redhat.com> wrote:

> Suppose that "event_indicated = 1" leaks into try_to_wake_up() after we
> read p->state.

In that case, it's entirely possible that the smp_wmb() in try_to_wake_up()
should actually be an smp_mb(), but that on whichever arch patch:

	commit 04e2f1741d235ba599037734878d72e57cb302b5
	Author: Linus Torvalds <torvalds@woody.linux-foundation.org>
	Date:   Sat Feb 23 18:05:03 2008 -0800
	Subject: Add memory barrier semantics to wake_up() & co

was tested on, it made no difference.

David