From: Oleg Nesterov <oleg@redhat.com>
To: David Howells <dhowells@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
David Miller <davem@davemloft.net>,
Serge Hallyn <serue@us.ibm.com>,
Steve Dickson <steved@redhat.com>,
Trond Myklebust <Trond.Myklebust@netapp.com>,
Al Viro <viro@zeniv.linux.org.uk>,
Daire Byrne <Daire.Byrne@framestore.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] slow_work_execute() needs mb() before test_bit(SLOW_WORK_PENDING)
Date: Thu, 16 Apr 2009 16:15:10 +0200 [thread overview]
Message-ID: <20090416141510.GC6532@redhat.com> (raw)
In-Reply-To: <14774.1239875022@redhat.com>
On 04/16, David Howells wrote:
>
> Oleg Nesterov <oleg@redhat.com> wrote:
>
> > But why do we need the barrier before clear_bit(SLOW_WORK_EXECUTING) ?
> > We do have one after test_and_clear_bit(SLOW_WORK_PENDING) above, and it
> > should be enough, no?
>
> No. There lock is covering work->ops->execute(work) too, and that is after
> the clearance of SLOW_WORK_PENDING. The UNLOCK-class barrier must go between
> execution and clearance of the execution lock bit.
Ah. Now I see.
It is still not clear to me whether we need a barrier after clear_bit_unlock.
Thanks David!
Oleg.
prev parent reply other threads:[~2009-04-16 14:19 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-04-13 20:13 [PATCH] slow_work_execute() needs mb() before test_bit(SLOW_WORK_PENDING) Oleg Nesterov
2009-04-13 20:13 ` Oleg Nesterov
2009-04-13 21:47 ` David Howells
2009-04-13 22:02 ` Oleg Nesterov
2009-04-16 9:43 ` David Howells
2009-04-16 14:15 ` Oleg Nesterov [this message]
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