From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752046AbdGaW7F (ORCPT ); Mon, 31 Jul 2017 18:59:05 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:48471 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751970AbdGaW6X (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" , Davidlohr Bueso , Will Deacon , Alan Stern , Andrea Parri , Linus Torvalds Subject: [PATCH v2 tip/core/rcu 07/10] ipc: Replace spin_unlock_wait() with lock/unlock pair Date: Mon, 31 Jul 2017 15:58:14 -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: 17073122-0024-0000-0000-000002B890EA X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00007461; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000214; SDB=6.00895722; UDB=6.00448017; IPR=6.00675909; 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 22:58:21 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17073122-0025-0000-0000-000044F18D9E Message-Id: <1501541897-5225-7-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 no agreed-upon definition of spin_unlock_wait()'s semantics, and it appears that all callers could do just as well with a lock/unlock pair. This commit therefore replaces the spin_unlock_wait() call in exit_sem() with spin_lock() followed immediately by spin_unlock(). This should be safe from a performance perspective because exit_sem() is rarely invoked in production. Signed-off-by: Paul E. McKenney Cc: Andrew Morton Cc: Davidlohr Bueso Cc: Will Deacon Cc: Peter Zijlstra Cc: Alan Stern Cc: Andrea Parri Cc: Linus Torvalds Acked-by: Manfred Spraul --- ipc/sem.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/ipc/sem.c b/ipc/sem.c index 9e70cd7a17da..2570830e29fc 100644 --- a/ipc/sem.c +++ b/ipc/sem.c @@ -2091,7 +2091,8 @@ void exit_sem(struct task_struct *tsk) * possibility where we exit while freeary() didn't * finish unlocking sem_undo_list. */ - spin_unlock_wait(&ulp->lock); + spin_lock(&ulp->lock); + spin_unlock(&ulp->lock); rcu_read_unlock(); break; } -- 2.5.2