From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932604AbdGXWN4 (ORCPT ); Mon, 24 Jul 2017 18:13:56 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:49786 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932221AbdGXWNQ (ORCPT ); Mon, 24 Jul 2017 18:13:16 -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 tip/core/rcu 6/9] ipc: Replace spin_unlock_wait() with lock/unlock pair Date: Mon, 24 Jul 2017 15:13:06 -0700 X-Mailer: git-send-email 2.5.2 In-Reply-To: <20170724221252.GA14238@linux.vnet.ibm.com> References: <20170724221252.GA14238@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 17072422-0056-0000-0000-000003AC0ACF X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00007419; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000214; SDB=6.00892382; UDB=6.00446027; IPR=6.00672546; BA=6.00005489; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00016356; XFM=3.00000015; UTC=2017-07-24 22:13:13 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17072422-0057-0000-0000-000007E227D8 Message-Id: <1500934389-14942-6-git-send-email-paulmck@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-07-24_14:,, 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-1707240340 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