From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [PATCHv5 2/2] memory barrier: adding smp_mb__after_lock
Date: Tue, 07 Jul 2009 17:50:15 +0200
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Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>,
	Jiri Olsa <jolsa@redhat.com>, Ingo Molnar <mingo@elte.hu>,
	Eric Dumazet <eric.dumazet@gmail.com>, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org, fbl@redhat.com, nhorman@redhat.com,
	davem@redhat.com, htejun@gmail.com, jarkao2@gmail.com,
	davidel@xmailserver.org
To: Oleg Nesterov <oleg@redhat.com>
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On Tue, 2009-07-07 at 17:44 +0200, Oleg Nesterov wrote:
> On 07/07, Mathieu Desnoyers wrote:
> >
> > Actually, thinking about it more, to appropriately support x86, as well
> > as powerpc, arm and mips, we would need something like:
> >
> > read_lock_smp_mb()
> >
> > Which would be a read_lock with an included memory barrier.
> 
> Then we need read_lock_irq_smp_mb, read_lock_irqsave__smp_mb, write_lock_xxx,
> otherwise it is not clear why only read_lock() has _smp_mb() version.
> 
> The same for spin_lock_xxx...

At which time the smp_mb__{before,after}_{un,}lock become attractive
again.