From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752072AbdHKEzB (ORCPT ); Fri, 11 Aug 2017 00:55:01 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:49620 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751233AbdHKEy7 (ORCPT ); Fri, 11 Aug 2017 00:54:59 -0400 Date: Thu, 10 Aug 2017 21:54:53 -0700 From: "Paul E. McKenney" To: Stephen Rothwell Cc: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Peter Zijlstra , Linux-Next Mailing List , Linux Kernel Mailing List Subject: Re: linux-next: build failure after merge of the rcu tree Reply-To: paulmck@linux.vnet.ibm.com References: <20170811144352.585085e2@canb.auug.org.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170811144352.585085e2@canb.auug.org.au> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 17081104-0052-0000-0000-0000024E2FC2 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00007523; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000219; SDB=6.00900611; UDB=6.00450902; IPR=6.00680813; BA=6.00005522; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00016640; XFM=3.00000015; UTC=2017-08-11 04:54:57 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17081104-0053-0000-0000-000051A24C06 Message-Id: <20170811045453.GB3730@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-08-11_03:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1706020000 definitions=main-1708110080 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 11, 2017 at 02:43:52PM +1000, Stephen Rothwell wrote: > Hi Paul, > > After merging the rcu tree, today's linux-next build (arm > multi_v7_defconfig) failed like this: > > kernel/sched/core.c: In function 'do_task_dead': > kernel/sched/core.c:3385:2: error: implicit declaration of function 'smp_mb__before_spinlock' [-Werror=implicit-function-declaration] > smp_mb__before_spinlock(); > ^ > cc1: some warnings being treated as errors > > Caused by commit > > 4a6fc6107e90 ("sched: Replace spin_unlock_wait() with lock/unlock pair") > > Interacting with commit > > a9668cd6ee28 ("locking: Remove smp_mb__before_spinlock()") > > from the tip tree. > > I applied this patch for now, but I assume something better is required. Looks like I need to rebase my patch on top of a9668cd6ee28, and than put an smp_mb__after_spinlock() between the lock and the unlock. Peter, any objections to that approach? Other suggestions? Thanx, Paul > From: Stephen Rothwell > Date: Fri, 11 Aug 2017 14:32:10 +1000 > Subject: [PATCH] sched: temporary hack for locking: Remove smp_mb__before_spinlock() > > Signed-off-by: Stephen Rothwell > --- > kernel/sched/core.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 2bd00feaea15..a4f4ba2e3be6 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -3382,7 +3382,7 @@ void __noreturn do_task_dead(void) > * To avoid it, we have to wait for releasing tsk->pi_lock which > * is held by try_to_wake_up() > */ > - smp_mb__before_spinlock(); > + smp_mb(); > raw_spin_lock_irq(¤t->pi_lock); > raw_spin_unlock_irq(¤t->pi_lock); > > -- > Cheers, > Stephen Rothwell >