From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: Re: [PATCH RFC 06/26] ipc: Replace spin_unlock_wait() with lock/unlock pair Date: Sat, 1 Jul 2017 20:16:24 -0700 Message-ID: <20170702031624.GS2393@linux.vnet.ibm.com> References: <20170629235918.GA6445@linux.vnet.ibm.com> <1498780894-8253-6-git-send-email-paulmck@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-kernel@vger.kernel.org, netfilter-devel@vger.kernel.org, netdev@vger.kernel.org, oleg@redhat.com, akpm@linux-foundation.org, mingo@redhat.com, dave@stgolabs.net, 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 To: Manfred Spraul Return-path: Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:36824 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752374AbdGBDQb (ORCPT ); Sat, 1 Jul 2017 23:16:31 -0400 Received: from pps.filterd (m0098409.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v623Dcec140634 for ; Sat, 1 Jul 2017 23:16:30 -0400 Received: from e14.ny.us.ibm.com (e14.ny.us.ibm.com [129.33.205.204]) by mx0a-001b2d01.pphosted.com with ESMTP id 2ber5jguxv-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Sat, 01 Jul 2017 23:16:30 -0400 Received: from localhost by e14.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Sat, 1 Jul 2017 23:16:29 -0400 Content-Disposition: inline In-Reply-To: Sender: netfilter-devel-owner@vger.kernel.org List-ID: On Sat, Jul 01, 2017 at 09:23:03PM +0200, Manfred Spraul wrote: > On 06/30/2017 02:01 AM, Paul E. McKenney wrote: > >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: Manfred Spraul > >Cc: Will Deacon > >Cc: Peter Zijlstra > >Cc: Alan Stern > >Cc: Andrea Parri > >Cc: Linus Torvalds > Acked-by: Manfred Spraul Applied, thank you! Thanx, Paul > >--- > > 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; > > } > >