From: Peter Zijlstra <peterz@infradead.org>
To: Gautham R Shenoy <ego@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Tejun Heo <htejun@gmail.com>,
Michael Ellerman <mpe@ellerman.id.au>,
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: Wed, 15 Jun 2016 13:32:49 +0200 [thread overview]
Message-ID: <20160615113249.GH30909@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20160615101936.GA31671@in.ibm.com>
On Wed, Jun 15, 2016 at 03:49:36PM +0530, Gautham R Shenoy wrote:
> Also, with the first patch in the series (which ensures that
> restore_unbound_workers are called *after* the new workers for the
> newly onlined CPUs are created) and without this one, you can
> reproduce this WARN_ON on both x86 and PPC by offlining all the CPUs
> of a node and bringing just one of them online.
Ah good.
> I am not sure about that. The workqueue creates unbound workers for a
> node via wq_update_unbound_numa() whenever the first CPU of every node
> comes online. So that seems legitimate. It then tries to affine these
> workers to the cpumask of that node. Again this seems right. As an
> optimization, it does this only when the first CPU of the node comes
> online. Since this online CPU is not yet active, and since
> nr_cpus_allowed > 1, we will hit the WARN_ON().
So I had another look and isn't the below a much simpler solution?
It seems to work on my x86 with:
for i in /sys/devices/system/cpu/cpu*/online ; do echo 0 > $i ; done
for i in /sys/devices/system/cpu/cpu*/online ; do echo 1 > $i ; done
without complaint.
---
kernel/workqueue.c | 14 +++++---------
1 file changed, 5 insertions(+), 9 deletions(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index e1c0e99..09c9160 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -4600,15 +4600,11 @@ static void restore_unbound_workers_cpumask(struct worker_pool *pool, int cpu)
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);
}
/*
@@ -4638,6 +4634,10 @@ static int workqueue_cpu_up_callback(struct notifier_block *nfb,
case CPU_ONLINE:
mutex_lock(&wq_pool_mutex);
+ /* update NUMA affinity of unbound workqueues */
+ list_for_each_entry(wq, &workqueues, list)
+ wq_update_unbound_numa(wq, cpu, true);
+
for_each_pool(pool, pi) {
mutex_lock(&pool->attach_mutex);
@@ -4649,10 +4649,6 @@ static int workqueue_cpu_up_callback(struct notifier_block *nfb,
mutex_unlock(&pool->attach_mutex);
}
- /* update NUMA affinity of unbound workqueues */
- list_for_each_entry(wq, &workqueues, list)
- wq_update_unbound_numa(wq, cpu, true);
-
mutex_unlock(&wq_pool_mutex);
break;
}
next prev parent reply other threads:[~2016-06-15 11:33 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 [this message]
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
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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