From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: [PATCH RFC 05/26] exit: Replace spin_unlock_wait() with lock/unlock pair Date: Thu, 29 Jun 2017 17:01:13 -0700 Message-ID: <1498780894-8253-5-git-send-email-paulmck@linux.vnet.ibm.com> References: <20170629235918.GA6445@linux.vnet.ibm.com> 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" , Ingo Molnar To: linux-kernel@vger.kernel.org Return-path: Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:59742 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751899AbdF3ABo (ORCPT ); Thu, 29 Jun 2017 20:01:44 -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 v5TNx63q012372 for ; Thu, 29 Jun 2017 20:01:43 -0400 Received: from e11.ny.us.ibm.com (e11.ny.us.ibm.com [129.33.205.201]) by mx0a-001b2d01.pphosted.com with ESMTP id 2bd34cdew1-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Thu, 29 Jun 2017 20:01:43 -0400 Received: from localhost by e11.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 In-Reply-To: <20170629235918.GA6445@linux.vnet.ibm.com> Sender: netfilter-devel-owner@vger.kernel.org List-ID: 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 do_exit() with spin_lock() followed immediately by spin_unlock(). This should be safe from a performance perspective because the lock is a per-task lock, and this is happening only at task-exit time. Signed-off-by: Paul E. McKenney Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Will Deacon Cc: Alan Stern Cc: Andrea Parri Cc: Linus Torvalds --- kernel/exit.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/exit.c b/kernel/exit.c index 516acdb0e0ec..1a976e47ddd1 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -832,7 +832,8 @@ void __noreturn do_exit(long code) * Ensure that we must observe the pi_state in exit_mm() -> * mm_release() -> exit_pi_state_list(). */ - raw_spin_unlock_wait(&tsk->pi_lock); + raw_spin_lock(&tsk->pi_lock); + raw_spin_unlock(&tsk->pi_lock); if (unlikely(in_atomic())) { pr_info("note: %s[%d] exited with preempt_count %d\n", -- 2.5.2