From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933549AbcFMFoR (ORCPT ); Mon, 13 Jun 2016 01:44:17 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:47425 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750803AbcFMFoQ (ORCPT ); Mon, 13 Jun 2016 01:44:16 -0400 X-IBM-Helo: d03dlp03.boulder.ibm.com X-IBM-MailFrom: ego@linux.vnet.ibm.com X-IBM-RcptTo: mpe@ellerman.id.au;htejun@gmail.com;peterz@infradead.org;tglx@linutronix.de;linuxppc-dev@lists.ozlabs.org;linux-kernel@vger.kernel.org Date: Mon, 13 Jun 2016 11:14:04 +0530 From: Gautham R Shenoy To: "Gautham R. Shenoy" Cc: Peter Zijlstra , Thomas Gleixner , Tejun Heo , Michael Ellerman , Abdul Haleem , Aneesh Kumar , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/2] Fix CPU Online handling for unbounded worker threads Reply-To: ego@linux.vnet.ibm.com References: <5756BE20.3040208@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) X-TM-AS-GCONF: 00 X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16061305-0016-0000-0000-000003EC723B X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 16061305-0017-0000-0000-00003023197F Message-Id: <20160613054404.GA18423@in.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-06-13_02:,, 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=8.0.1-1604210000 definitions=main-1606130063 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Peter, Thomas, On Tue, Jun 07, 2016 at 08:44:01PM +0530, Gautham R. Shenoy wrote: > Hi, > > This patchset fixes a couple of issues in the CPU_ONLINE notification > handling for the workqueues with respect to unbounded worker threads. Any thoughts on these patches ? They fix a race which was causing WARN_ON() to be consistently reproduced on POWER machines since 4.6. Could you please review these patches ? -- Thanks and Regard gautham. > > Patch 1 ensures that the affinity of a unbound worker thread > associated with a node whose very first CPU has come online is set > correctly. In the existing code path we will never call > set_cpus_allowed_ptr() for unbound worker threads that have been > created on a CPU Online operation after boot. > > Patch 2 fixes the following WARN_ON() reported by Abdul when > set_cpus_allowed_ptr() for an unbound worker thread is invoked when > only one of the CPUs in its cpumask is online but not yet active. > > ------------[ cut here ]------------ > WARNING: CPU: 40 PID: 248 at kernel/sched/core.c:1166 __set_cpus_allowed_ptr+0x21c/0x290 > Modules linked in: > CPU: 40 PID: 248 Comm: cpuhp/40 Not tainted 4.6.0-autotest #1 > task: c000000f27284200 ti: c000000f273fc000 task.ti: c000000f273fc000 > NIP: c00000000010488c LR: c000000000104874 CTR: 0000000000000000 > REGS: c000000f273ff7d0 TRAP: 0700 Not tainted (4.6.0-autotest) > MSR: 9000000100029033 CR: 28002804 XER: 20000000 > CFAR: c0000000005b0888 SOFTE: 0 > GPR00: c00000000010478c c000000f273ffa50 c0000000013ce400 0000000000000000 > GPR04: c00000000140ed98 0000000000000800 c0000007f64d9408 0000000000000000 > GPR08: 0000000000000000 0000000000000028 c00000000140ee90 0000000000000020 > GPR12: 0000000000002200 c00000000fb96800 c0000000000f44a8 c0000007fa158480 > GPR16: c0000007fc621a70 c000000f2721f800 0000000000000000 0000000000000001 > GPR20: c000000001571ef0 0000000000000000 c00000000134879f c0000000012bc510 > GPR24: 0000010000000000 0000000000000000 c00000000140ea98 c0000007f64d9408 > GPR28: c0000007fbc21c00 ffffffffffffffea 0000000000000000 c000000f27280000 > NIP [c00000000010488c] __set_cpus_allowed_ptr+0x21c/0x290 > LR [c000000000104874] __set_cpus_allowed_ptr+0x204/0x290 > Call Trace: > [c000000f273ffa50] [c00000000010478c] __set_cpus_allowed_ptr+0x11c/0x290 (unreliable) > [c000000f273ffac0] [c0000000000ed4b0] workqueue_cpu_up_callback+0x2c0/0x470 > [c000000f273ffb70] [c0000000000f5c58] notifier_call_chain+0x98/0x100 > [c000000f273ffbc0] [c0000000000c5ed0] __cpu_notify+0x70/0xe0 > [c000000f273ffc00] [c0000000000c6028] notify_online+0x38/0x50 > [c000000f273ffc30] [c0000000000c5214] cpuhp_invoke_callback+0x84/0x250 > [c000000f273ffc90] [c0000000000c562c] cpuhp_up_callbacks+0x5c/0x120 > [c000000f273ffce0] [c0000000000c64d4] cpuhp_thread_fun+0x184/0x1c0 > [c000000f273ffd20] [c0000000000fa050] smpboot_thread_fn+0x290/0x2a0 > [c000000f273ffd80] [c0000000000f45b0] kthread+0x110/0x130 > [c000000f273ffe30] [c000000000009570] ret_from_kernel_thread+0x5c/0x6c > Instruction dump: > 419eff3c 3d420004 38a00800 388a0998 7f63db78 484abfa1 60000000 2fa30000 > 409eff1c 813f0378 2f890001 419eff10 <0fe00000> 4bffff08 60000000 60000000 > ---[ end trace cbc1c5cfbc9591d0 ]--- > > The patches are based on 4.7-rc2. I have tested the patches on a > multi-node x86_64 and a ppc64 > > Gautham R. Shenoy (2): > workqueue: Move wq_update_unbound_numa() to the beginning of > CPU_ONLINE > workqueue:Fix affinity of an unbound worker of a node with 1 online > CPU > > kernel/workqueue.c | 27 +++++++++++++++++++-------- > 1 file changed, 19 insertions(+), 8 deletions(-) > > -- > 1.9.3 >