From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: [PATCH RFC 02/26] task_work: Replace spin_unlock_wait() with lock/unlock pair Date: Thu, 29 Jun 2017 17:01:10 -0700 Message-ID: <1498780894-8253-2-git-send-email-paulmck@linux.vnet.ibm.com> References: <20170629235918.GA6445@linux.vnet.ibm.com> Return-path: In-Reply-To: <20170629235918.GA6445@linux.vnet.ibm.com> Sender: linux-kernel-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 task_work_run() with spin_lock() followed immediately by spin_unlock(). This should be safe from a performance perspective because calls to the other side of the race, task_work_cancel(), should be rare. Signed-off-by: Paul E. McKenney Cc: Oleg Nesterov Cc: Andrew Morton Cc: Will Deacon Cc: Peter Zijlstra Cc: Alan Stern Cc: Andrea Parri Cc: Linus Torvalds --- kernel/task_work.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/task_work.c b/kernel/task_work.c index d513051fcca2..b9b428832229 100644 --- a/kernel/task_work.c +++ b/kernel/task_work.c @@ -109,7 +109,8 @@ void task_work_run(void) * the first entry == work, cmpxchg(task_works) should * fail, but it can play with *work and other entries. */ - raw_spin_unlock_wait(&task->pi_lock); + raw_spin_lock(&task->pi_lock); + raw_spin_unlock(&task->pi_lock); do { next = work->next; -- 2.5.2 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:36301 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751722AbdF3ABn (ORCPT ); Thu, 29 Jun 2017 20:01:43 -0400 Received: from pps.filterd (m0098413.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v5TNxBQE055148 for ; Thu, 29 Jun 2017 20:01:43 -0400 Received: from e19.ny.us.ibm.com (e19.ny.us.ibm.com [129.33.205.209]) by mx0b-001b2d01.pphosted.com with ESMTP id 2bcyr8yf72-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Thu, 29 Jun 2017 20:01:42 -0400 Received: from localhost by e19.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 29 Jun 2017 20:01:42 -0400 From: "Paul E. McKenney" Subject: [PATCH RFC 02/26] task_work: Replace spin_unlock_wait() with lock/unlock pair Date: Thu, 29 Jun 2017 17:01:10 -0700 In-Reply-To: <20170629235918.GA6445@linux.vnet.ibm.com> References: <20170629235918.GA6445@linux.vnet.ibm.com> Message-ID: <1498780894-8253-2-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: <20170630000110.qcOpgH_ddKrlJrtlwxTupI1pTA11ZEZ7kxSvUZf1AVY@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 task_work_run() with spin_lock() followed immediately by spin_unlock(). This should be safe from a performance perspective because calls to the other side of the race, task_work_cancel(), should be rare. Signed-off-by: Paul E. McKenney Cc: Oleg Nesterov Cc: Andrew Morton Cc: Will Deacon Cc: Peter Zijlstra Cc: Alan Stern Cc: Andrea Parri Cc: Linus Torvalds --- kernel/task_work.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/task_work.c b/kernel/task_work.c index d513051fcca2..b9b428832229 100644 --- a/kernel/task_work.c +++ b/kernel/task_work.c @@ -109,7 +109,8 @@ void task_work_run(void) * the first entry == work, cmpxchg(task_works) should * fail, but it can play with *work and other entries. */ - raw_spin_unlock_wait(&task->pi_lock); + raw_spin_lock(&task->pi_lock); + raw_spin_unlock(&task->pi_lock); do { next = work->next; -- 2.5.2