Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759674AbZCWU6L (ORCPT ); Mon, 23 Mar 2009 16:58:11 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759107AbZCWU5V (ORCPT ); Mon, 23 Mar 2009 16:57:21 -0400 Received: from hera.kernel.org ([140.211.167.34]:49081 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758830AbZCWU5U (ORCPT ); Mon, 23 Mar 2009 16:57:20 -0400 Date: Mon, 23 Mar 2009 20:56:49 GMT From: Eric Paris To: linux-tip-commits@vger.kernel.org Cc: linux-kernel@vger.kernel.org, paulus@samba.org, hpa@zytor.com, mingo@redhat.com, a.p.zijlstra@chello.nl, eparis@redhat.com, tglx@linutronix.de, mingo@elte.hu Reply-To: mingo@redhat.com, hpa@zytor.com, paulus@samba.org, linux-kernel@vger.kernel.org, eparis@redhat.com, a.p.zijlstra@chello.nl, tglx@linutronix.de, mingo@elte.hu In-Reply-To: <20090323172417.410913479@chello.nl> References: <20090323172417.410913479@chello.nl> Subject: [tip:perfcounters/core] mutex: add atomic_dec_and_mutex_lock() Message-ID: Git-Commit-ID: 3a2d367d9aabac486ac4444c6c7ec7a1dab16267 X-Mailer: tip-git-log-daemon MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.0 (hera.kernel.org [127.0.0.1]); Mon, 23 Mar 2009 20:56:51 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2113 Lines: 61 Commit-ID: 3a2d367d9aabac486ac4444c6c7ec7a1dab16267 Gitweb: http://git.kernel.org/tip/3a2d367d9aabac486ac4444c6c7ec7a1dab16267 Author: Eric Paris AuthorDate: Mon, 23 Mar 2009 18:22:09 +0100 Committer: Ingo Molnar CommitDate: Mon, 23 Mar 2009 21:45:10 +0100 mutex: add atomic_dec_and_mutex_lock() Much like the atomic_dec_and_lock() function in which we take an hold a spin_lock if we drop the atomic to 0 this function takes and holds the mutex if we dec the atomic to 0. Signed-off-by: Eric Paris Signed-off-by: Peter Zijlstra Cc: Paul Mackerras LKML-Reference: <20090323172417.410913479@chello.nl> Signed-off-by: Ingo Molnar --- include/linux/mutex.h | 23 +++++++++++++++++++++++ 1 files changed, 23 insertions(+), 0 deletions(-) diff --git a/include/linux/mutex.h b/include/linux/mutex.h index 3069ec7..93054fc 100644 --- a/include/linux/mutex.h +++ b/include/linux/mutex.h @@ -151,4 +151,27 @@ extern int __must_check mutex_lock_killable(struct mutex *lock); extern int mutex_trylock(struct mutex *lock); extern void mutex_unlock(struct mutex *lock); +/** + * atomic_dec_and_mutex_lock - return holding mutex if we dec to 0 + * @cnt: the atomic which we are to dec + * @lock: the mutex to return holding if we dec to 0 + * + * return true and hold lock if we dec to 0, return false otherwise + */ +static inline int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock) +{ + /* dec if we can't possibly hit 0 */ + if (atomic_add_unless(cnt, -1, 1)) + return 0; + /* we might hit 0, so take the lock */ + mutex_lock(lock); + if (!atomic_dec_and_test(cnt)) { + /* when we actually did the dec, we didn't hit 0 */ + mutex_unlock(lock); + return 0; + } + /* we hit 0, and we hold the lock */ + return 1; +} + #endif -- 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/