From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e35.co.us.ibm.com (e35.co.us.ibm.com [32.97.110.153]) (using TLSv1.2 with cipher CAMELLIA256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3rPdD667pQzDq5m for ; Wed, 8 Jun 2016 16:03:48 +1000 (AEST) Received: from localhost by e35.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 8 Jun 2016 00:03:46 -0600 Subject: Re: [PATCH 2/2] workqueue:Fix affinity of an unbound worker of a node with 1 online CPU To: "Gautham R. Shenoy" , Peter Zijlstra , Thomas Gleixner , Tejun Heo , Michael Ellerman , Aneesh Kumar References: <5756BE20.3040208@linux.vnet.ibm.com> Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org From: Abdul Haleem Message-ID: <5757B538.1010806@linux.vnet.ibm.com> Date: Wed, 8 Jun 2016 11:33:36 +0530 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252; format=flowed List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hi Gautham, Thanks a lot for the fix. With your patches applied, 4.7.0-rc2 builds fine on ppc64le bare metal. Boot was successful with No call traces. Thanks for all your support ! Regard's Abdul On Tuesday 07 June 2016 08:44 PM, Gautham R. Shenoy wrote: > With commit e9d867a67fd03ccc ("sched: Allow per-cpu kernel threads to > run on online && !active"), __set_cpus_allowed_ptr() expects that only > strict per-cpu kernel threads can have affinity to an online CPU which > is not yet active. > > This assumption is currently broken in the CPU_ONLINE notification > handler for the workqueues where restore_unbound_workers_cpumask() > calls set_cpus_allowed_ptr() when the first cpu in the unbound > worker's pool->attr->cpumask comes online. Since > set_cpus_allowed_ptr() is called with pool->attr->cpumask in which > only one CPU is online which is not yet active, we get the following > WARN_ON during an CPU online operation. > > ------------[ cut here ]------------ > WARNING: CPU: 40 PID: 248 at kernel/sched/core.c:1166 > __set_cpus_allowed_ptr+0x228/0x2e0 > Modules linked in: > CPU: 40 PID: 248 Comm: cpuhp/40 Not tainted 4.6.0-autotest+ #4 > <..snip..> > Call Trace: > [c000000f273ff920] [c00000000010493c] __set_cpus_allowed_ptr+0x2cc/0x2e0 (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 > ---[ end trace 00f1456578b2a3b2 ]--- > > This patch sets the affinity of the worker to > a) the only online CPU in the cpumask of the worker pool when it comes > online. > b) the cpumask of the worker pool when the second CPU in the pool's > cpumask comes online. > > Reported-by: Abdul Haleem > Cc: Peter Zijlstra > Cc: Thomas Gleixner > Cc: Tejun Heo > Cc: Michael Ellerman > Signed-off-by: Gautham R. Shenoy > ---