From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757737AbZF3LOu (ORCPT ); Tue, 30 Jun 2009 07:14:50 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752758AbZF3LOo (ORCPT ); Tue, 30 Jun 2009 07:14:44 -0400 Received: from gw1.cosmosbay.com ([212.99.114.194]:35349 "EHLO gw1.cosmosbay.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752134AbZF3LOn (ORCPT ); Tue, 30 Jun 2009 07:14:43 -0400 Message-ID: <4A49F38C.80104@gmail.com> Date: Tue, 30 Jun 2009 13:14:20 +0200 From: Eric Dumazet User-Agent: Thunderbird 2.0.0.22 (Windows/20090605) MIME-Version: 1.0 To: Jiri Olsa 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, eric.dumazet@gmail.com Subject: Re: [PATCHv2 2/2] memory barrier: adding smp_mb__after_lock References: <20090630103642.GB9657@jolsa.lab.eng.brq.redhat.com> <20090630104106.GD9657@jolsa.lab.eng.brq.redhat.com> In-Reply-To: <20090630104106.GD9657@jolsa.lab.eng.brq.redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-1.6 (gw1.cosmosbay.com [0.0.0.0]); Tue, 30 Jun 2009 13:14:30 +0200 (CEST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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())