Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758670AbZGHTuk (ORCPT ); Wed, 8 Jul 2009 15:50:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755152AbZGHTud (ORCPT ); Wed, 8 Jul 2009 15:50:33 -0400 Received: from mx2.redhat.com ([66.187.237.31]:42583 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754850AbZGHTuc (ORCPT ); Wed, 8 Jul 2009 15:50:32 -0400 Date: Wed, 8 Jul 2009 21:50:04 +0200 From: Jiri Olsa To: netdev@vger.kernel.org Cc: eric.dumazet@gmail.com, mathieu.desnoyers@polymtl.ca, mingo@elte.hu, a.p.zijlstra@chello.nl, linux-kernel@vger.kernel.org, fbl@redhat.com, nhorman@redhat.com, htejun@gmail.com, jarkao2@gmail.com, oleg@redhat.com, davidel@xmailserver.org, davem@davemloft.net Subject: [PATCH 2/2] [PATCHv6 2/2] memory barrier: adding smp_mb__after_lock Message-ID: <20090708195004.GC3196@jolsa.lab.eng.brq.redhat.com> References: <20090708194726.GA3196@jolsa.lab.eng.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090708194726.GA3196@jolsa.lab.eng.brq.redhat.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 Content-Length: 2524 Lines: 77 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 | 4 ++++ include/linux/spinlock.h | 5 +++++ include/net/sock.h | 5 ++++- 3 files changed, 13 insertions(+), 1 deletions(-) diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h index b7e5db8..4e77853 100644 --- a/arch/x86/include/asm/spinlock.h +++ b/arch/x86/include/asm/spinlock.h @@ -302,4 +302,8 @@ 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. */ +static inline void smp_mb__after_lock(void) { } +#define ARCH_HAS_SMP_MB_AFTER_LOCK + #endif /* _ASM_X86_SPINLOCK_H */ diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h index 252b245..4be57ab 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 ARCH_HAS_SMP_MB_AFTER_LOCK +static inline void smp_mb__after_lock(void) { 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..2c0da92 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -1271,6 +1271,9 @@ static inline int sk_has_allocations(const struct sock *sk) * in its cache, and so does the tp->rcv_nxt update on CPU2 side. The CPU1 * could then endup calling schedule and sleep forever if there are no more * data on the socket. + * + * The sk_has_sleeper is always called right after a call to read_lock, so we + * can use smp_mb__after_lock barrier. */ static inline int sk_has_sleeper(struct sock *sk) { @@ -1280,7 +1283,7 @@ 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); } -- 1.6.2.5 -- 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/