From: Peter Zijlstra <peterz@infradead.org>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: Tejun Heo <htejun@gmail.com>,
Gautham R Shenoy <ego@linux.vnet.ibm.com>,
Thomas Gleixner <tglx@linutronix.de>,
Abdul Haleem <abdhalee@linux.vnet.ibm.com>,
Aneesh Kumar <aneesh.kumar@linux.vnet.ibm.com>,
linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] workqueue:Fix affinity of an unbound worker of a node with 1 online CPU
Date: Thu, 16 Jun 2016 14:45:48 +0200 [thread overview]
Message-ID: <20160616124548.GE30921@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <1466079084.19127.2.camel@ellerman.id.au>
On Thu, Jun 16, 2016 at 10:11:24PM +1000, Michael Ellerman wrote:
> Peterz do you want to send a SOB'ed patch, or can we take what you posted and
> add your SOB?
So I took Ego's first patch, so as to not steal his credits take that
one and then see below.
---
Subject: workqueue: Fix setting affinity of unbound worker threads
From: Peter Zijlstra <peterz@infradead.org>
Date: Thu Jun 16 14:38:42 CEST 2016
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 fixes this by limiting the mask to the intersection of
the pool affinity and online CPUs.
Changelog-cribbed-from: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Reported-by: Abdul Haleem <abdhalee@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
kernel/workqueue.c | 6 +-----
1 file changed, 1 insertion(+), 5 deletions(-)
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -4600,15 +4600,11 @@ static void restore_unbound_workers_cpum
if (!cpumask_test_cpu(cpu, pool->attrs->cpumask))
return;
- /* is @cpu the only online CPU? */
cpumask_and(&cpumask, pool->attrs->cpumask, cpu_online_mask);
- if (cpumask_weight(&cpumask) != 1)
- return;
/* as we're called from CPU_ONLINE, the following shouldn't fail */
for_each_pool_worker(worker, pool)
- WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task,
- pool->attrs->cpumask) < 0);
+ WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, &cpumask) < 0);
}
/*
next prev parent reply other threads:[~2016-06-16 12:46 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <573D9C2D.4020609@linux.vnet.ibm.com>
[not found] ` <20160526151137.GA26508@in.ibm.com>
2016-06-07 12:29 ` WARNING at kernel/sched/core.c:1166 while booting 4.6.0 mainline on ppc64le bare metal Abdul Haleem
2016-06-07 15:14 ` [PATCH 0/2] Fix CPU Online handling for unbounded worker threads Gautham R. Shenoy
2016-06-07 15:14 ` [PATCH 1/2] workqueue: Move wq_update_unbound_numa() to the beginning of CPU_ONLINE Gautham R. Shenoy
2016-06-15 15:53 ` Tejun Heo
2016-06-15 19:28 ` Gautham R Shenoy
2016-06-16 19:35 ` Tejun Heo
2016-06-21 14:12 ` Gautham R Shenoy
2016-06-21 15:36 ` Tejun Heo
2016-06-21 19:37 ` Peter Zijlstra
2016-06-21 19:43 ` Tejun Heo
2016-06-21 19:47 ` Peter Zijlstra
2016-06-22 5:15 ` Gautham R Shenoy
2016-06-24 9:00 ` [tip:sched/urgent] sched/core: Allow kthreads to fall back to online && !active cpus tip-bot for Tejun Heo
2016-06-07 15:14 ` [PATCH 2/2] workqueue:Fix affinity of an unbound worker of a node with 1 online CPU Gautham R. Shenoy
2016-06-08 6:03 ` Abdul Haleem
2016-06-14 11:22 ` Peter Zijlstra
2016-06-15 10:19 ` Gautham R Shenoy
2016-06-15 11:32 ` Peter Zijlstra
2016-06-15 12:50 ` Gautham R Shenoy
2016-06-15 13:14 ` Peter Zijlstra
2016-06-15 16:01 ` Tejun Heo
2016-06-16 12:11 ` Michael Ellerman
2016-06-16 12:45 ` Peter Zijlstra [this message]
2016-06-16 19:39 ` Tejun Heo
2016-06-17 1:49 ` Michael Ellerman
2016-07-15 5:27 ` Gautham R Shenoy
[not found] ` <57887507.911f240a.687de.08c5SMTPIN_ADDED_BROKEN@mx.google.com>
2016-07-15 12:10 ` Tejun Heo
2016-06-13 5:44 ` [PATCH 0/2] Fix CPU Online handling for unbounded worker threads Gautham R Shenoy
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