Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753067AbZGBGzO (ORCPT ); Thu, 2 Jul 2009 02:55:14 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751906AbZGBGy7 (ORCPT ); Thu, 2 Jul 2009 02:54:59 -0400 Received: from gw1.cosmosbay.com ([212.99.114.194]:53732 "EHLO gw1.cosmosbay.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750881AbZGBGy6 (ORCPT ); Thu, 2 Jul 2009 02:54:58 -0400 Message-ID: <4A4C5983.7000501@gmail.com> Date: Thu, 02 Jul 2009 08:53:55 +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: [PATCHv4 2/2] memory barrier: adding smp_mb__after_lock References: <20090702063259.GA3429@jolsa.lab.eng.brq.redhat.com> <20090702063624.GC3429@jolsa.lab.eng.brq.redhat.com> In-Reply-To: <20090702063624.GC3429@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]); Thu, 02 Jul 2009 08:53:59 +0200 (CEST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2423 Lines: 80 Jiri Olsa a ?crit : > 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 Maybe we should remind that sk_has_helper() is always called right after a call to read_lock() as in : read_lock(&sk->sk_callback_lock); if (sk_has_sleeper(sk)) wake_up_interruptible_all(sk->sk_sleep); Signed-off-by: Eric Dumazet Thanks Jiri > > --- > 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 4eb8409..b3e96a4 100644 > --- a/include/net/sock.h > +++ b/include/net/sock.h > @@ -1280,7 +1280,7 @@ static inline int sk_has_sleeper(struct sock *sk) > * > * This memory barrier is paired in the sock_poll_wait. > */ > - smp_mb(); > + smp_mb__after_lock(); > return sk->sk_sleep && waitqueue_active(sk->sk_sleep); > } > > -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/