From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: [PATCH v3 6/9] ipc: Replace spin_unlock_wait() with lock/unlock pair Date: Fri, 7 Jul 2017 12:28:23 -0700 Message-ID: <1499455706-9398-6-git-send-email-paulmck@linux.vnet.ibm.com> References: <20170707192704.GA6144@linux.vnet.ibm.com> Return-path: In-Reply-To: <20170707192704.GA6144@linux.vnet.ibm.com> Sender: netdev-owner@vger.kernel.org To: linux-kernel@vger.kernel.org Cc: netfilter-devel@vger.kernel.org, netdev@vger.kernel.org, oleg@redhat.com, akpm@linux-foundation.org, mingo@redhat.com, dave@stgolabs.net, manfred@colorfullife.com, tj@kernel.org, arnd@arndb.de, linux-arch@vger.kernel.org, will.deacon@arm.com, peterz@infradead.org, stern@rowland.harvard.edu, parri.andrea@gmail.com, torvalds@linux-foundation.org, "Paul E. McKenney" List-Id: linux-arch.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 947dc2348271..e88d0749a929 100644 --- a/ipc/sem.c +++ b/ipc/sem.c @@ -2096,7 +2096,8 @@ 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 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:54320 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752688AbdGGT3L (ORCPT ); Fri, 7 Jul 2017 15:29:11 -0400 Received: from pps.filterd (m0098404.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v67JSwED033082 for ; Fri, 7 Jul 2017 15:29:01 -0400 Received: from e18.ny.us.ibm.com (e18.ny.us.ibm.com [129.33.205.208]) by mx0a-001b2d01.pphosted.com with ESMTP id 2bjf19ty4p-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Fri, 07 Jul 2017 15:28:59 -0400 Received: from localhost by e18.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 7 Jul 2017 15:28:32 -0400 From: "Paul E. McKenney" Subject: [PATCH v3 6/9] ipc: Replace spin_unlock_wait() with lock/unlock pair Date: Fri, 7 Jul 2017 12:28:23 -0700 In-Reply-To: <20170707192704.GA6144@linux.vnet.ibm.com> References: <20170707192704.GA6144@linux.vnet.ibm.com> Message-ID: <1499455706-9398-6-git-send-email-paulmck@linux.vnet.ibm.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: linux-kernel@vger.kernel.org Cc: netfilter-devel@vger.kernel.org, netdev@vger.kernel.org, oleg@redhat.com, akpm@linux-foundation.org, mingo@redhat.com, dave@stgolabs.net, manfred@colorfullife.com, tj@kernel.org, arnd@arndb.de, linux-arch@vger.kernel.org, will.deacon@arm.com, peterz@infradead.org, stern@rowland.harvard.edu, parri.andrea@gmail.com, torvalds@linux-foundation.org, "Paul E. McKenney" Message-ID: <20170707192823.fHW2WfuTPiOWqH1EDAh2ZBbbIVAcnenlTZ4s86q_NZ0@z> 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 947dc2348271..e88d0749a929 100644 --- a/ipc/sem.c +++ b/ipc/sem.c @@ -2096,7 +2096,8 @@ 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