From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756397AbZF3MN0 (ORCPT ); Tue, 30 Jun 2009 08:13:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753046AbZF3MNV (ORCPT ); Tue, 30 Jun 2009 08:13:21 -0400 Received: from mx2.redhat.com ([66.187.237.31]:37184 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752974AbZF3MNU (ORCPT ); Tue, 30 Jun 2009 08:13:20 -0400 Date: Tue, 30 Jun 2009 14:13:18 +0200 From: Jiri Olsa To: Eric Dumazet Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, fbl@redhat.com, nhorman@redhat.com, davem@redhat.com, htejun@gmail.com, jarkao2@gmail.com, oleg@redhat.com, davidel@xmailserver.org Subject: Re: [PATCHv2 2/2] memory barrier: adding smp_mb__after_lock Message-ID: <20090630121318.GA4406@jolsa.lab.eng.brq.redhat.com> References: <20090630103642.GB9657@jolsa.lab.eng.brq.redhat.com> <20090630104106.GD9657@jolsa.lab.eng.brq.redhat.com> <4A49F38C.80104@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <4A49F38C.80104@gmail.com> User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jun 30, 2009 at 01:14:20PM +0200, Eric Dumazet wrote: > Jiri Olsa a écrit : > > Adding smp_mb__after_lock define to be used as a smp_mb call after > > a lock. > > > > Making it nop for x86, since {read|write|spin}_lock() on x86 are > > full memory barriers. > > > > wbr, > > jirka > > > > > > Signed-off-by: Jiri Olsa > > > > --- > > arch/x86/include/asm/spinlock.h | 3 +++ > > include/linux/spinlock.h | 5 +++++ > > include/net/sock.h | 2 +- > > 3 files changed, 9 insertions(+), 1 deletions(-) > > > > diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h > > index b7e5db8..39ecc5f 100644 > > --- a/arch/x86/include/asm/spinlock.h > > +++ b/arch/x86/include/asm/spinlock.h > > @@ -302,4 +302,7 @@ static inline void __raw_write_unlock(raw_rwlock_t *rw) > > #define _raw_read_relax(lock) cpu_relax() > > #define _raw_write_relax(lock) cpu_relax() > > > > +/* The {read|write|spin}_lock() on x86 are full memory barriers. */ > > +#define smp_mb__after_lock() do { } while (0) > > + > > #endif /* _ASM_X86_SPINLOCK_H */ > > diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h > > index 252b245..ae053bd 100644 > > --- a/include/linux/spinlock.h > > +++ b/include/linux/spinlock.h > > @@ -132,6 +132,11 @@ do { \ > > #endif /*__raw_spin_is_contended*/ > > #endif > > > > +/* The lock does not imply full memory barrier. */ > > +#ifndef smp_mb__after_lock > > +#define smp_mb__after_lock() smp_mb() > > +#endif > > + > > /** > > * spin_unlock_wait - wait until the spinlock gets unlocked > > * @lock: the spinlock in question. > > diff --git a/include/net/sock.h b/include/net/sock.h > > index a12df10..0d57e83 100644 > > --- a/include/net/sock.h > > +++ b/include/net/sock.h > > @@ -1277,7 +1277,7 @@ static inline void sock_poll_wait(struct file *filp, > > * > > * This memory barrier is paired in the sk_has_sleeper. > > */ > > - smp_mb(); > > + smp_mb__after_lock(); > > } > > } > > I believe you took wrong point to use this new thing :) > > It was meant to be used in sk_has_sleeper() only (as sk_has_sleeper() > follows a read_lock()) > shoot, you're right.. I'll resend 2/2, thanks jirka