From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752082AbdGaW7J (ORCPT ); Mon, 31 Jul 2017 18:59:09 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:53578 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751968AbdGaW6X (ORCPT ); Mon, 31 Jul 2017 18:58:23 -0400 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, "Paul E. McKenney" Subject: [PATCH v2 tip/core/rcu 01/10] atomics: Revert addition of comment header to spin_unlock_wait() Date: Mon, 31 Jul 2017 15:58:08 -0700 X-Mailer: git-send-email 2.5.2 In-Reply-To: <20170731225754.GB2674@linux.vnet.ibm.com> References: <20170731225754.GB2674@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 17073122-0036-0000-0000-000002519C3B X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00007461; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000214; SDB=6.00895723; UDB=6.00448017; IPR=6.00675910; BA=6.00005503; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00016472; XFM=3.00000015; UTC=2017-07-31 22:58:20 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17073122-0037-0000-0000-00004148ED35 Message-Id: <1501541897-5225-1-git-send-email-paulmck@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-07-31_09:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=1 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1706020000 definitions=main-1707310380 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org There is still considerable confusion as to the semantics of spin_unlock_wait(), but there seems to be universal agreement that it is not that of a lock/unlock pair. This commit therefore removes the comment added by 6016ffc3874d ("atomics: Add header comment so spin_unlock_wait()") in order to prevent at least that flavor of confusion. Signed-off-by: Paul E. McKenney --- include/linux/spinlock.h | 20 -------------------- 1 file changed, 20 deletions(-) diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h index d9510e8522d4..59248dcc6ef3 100644 --- a/include/linux/spinlock.h +++ b/include/linux/spinlock.h @@ -369,26 +369,6 @@ static __always_inline int spin_trylock_irq(spinlock_t *lock) raw_spin_trylock_irqsave(spinlock_check(lock), flags); \ }) -/** - * spin_unlock_wait - Interpose between successive critical sections - * @lock: the spinlock whose critical sections are to be interposed. - * - * Semantically this is equivalent to a spin_lock() immediately - * followed by a spin_unlock(). However, most architectures have - * more efficient implementations in which the spin_unlock_wait() - * cannot block concurrent lock acquisition, and in some cases - * where spin_unlock_wait() does not write to the lock variable. - * Nevertheless, spin_unlock_wait() can have high overhead, so if - * you feel the need to use it, please check to see if there is - * a better way to get your job done. - * - * The ordering guarantees provided by spin_unlock_wait() are: - * - * 1. All accesses preceding the spin_unlock_wait() happen before - * any accesses in later critical sections for this same lock. - * 2. All accesses following the spin_unlock_wait() happen after - * any accesses in earlier critical sections for this same lock. - */ static __always_inline void spin_unlock_wait(spinlock_t *lock) { raw_spin_unlock_wait(&lock->rlock); -- 2.5.2