Re: [PATCH 1/2] workqueue: Move wq_update_unbound_numa() to the beginning of CPU_ONLINE

From	Tejun Heo <htejun@gmail.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH 1/2] workqueue: Move wq_update_unbound_numa() to the beginning of CPU_ONLINE
Date	2016-06-21 17:40 +0200
Message-ID	<rMvWq-7DO-3@gated-at.bofh.it> (permalink)
References	(1 earlier) <rHqXo-4lt-39@gated-at.bofh.it> <rKlou-4sY-35@gated-at.bofh.it> <rKoFI-6BZ-13@gated-at.bofh.it> <rKLiV-3Wz-7@gated-at.bofh.it> <rMuH0-6Vn-41@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Tue, Jun 21, 2016 at 07:42:31PM +0530, Gautham R Shenoy wrote:
> > Subject: [PATCH] sched: allow kthreads to fallback to online && !active cpus
> > 
> > During CPU hotplug, CPU_ONLINE callbacks are run while the CPU is
> > online but not active.  A CPU_ONLINE callback may create or bind a
> > kthread so that its cpus_allowed mask only allows the CPU which is
> > being brought online.  The kthread may start executing before the CPU
> > is made active and can end up in select_fallback_rq().
> > 
> > In such cases, the expected behavior is selecting the CPU which is
> > coming online; however, because select_fallback_rq() only chooses from
> > active CPUs, it determines that the task doesn't have any viable CPU
> > in its allowed mask and ends up overriding it to cpu_possible_mask.
> > 
> > CPU_ONLINE callbacks should be able to put kthreads on the CPU which
> > is coming online.  Update select_fallback_rq() so that it follows
> > cpu_online() rather than cpu_active() for kthreads.
> > 
> > Signed-off-by: Tejun Heo <tj@kernel.org>
> > Reported-by: Gautham R Shenoy <ego@linux.vnet.ibm.com>
> 
> Hi Tejun,
> 
> This patch fixes the issue on POWER. I am able to see the worker
> threads of the unbound workqueues of the newly onlined node with this.
> 
> Tested-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>

Peter?

-- 
tejun

Thread

Re: [PATCH 1/2] workqueue: Move wq_update_unbound_numa() to the  beginning of CPU_ONLINE Tejun Heo <htejun@gmail.com> - 2016-06-15 18:00 +0200
  Re: [PATCH 1/2] workqueue: Move wq_update_unbound_numa() to the  beginning of CPU_ONLINE Gautham R Shenoy <ego@linux.vnet.ibm.com> - 2016-06-15 21:30 +0200
    Re: [PATCH 1/2] workqueue: Move wq_update_unbound_numa() to the  beginning of CPU_ONLINE Tejun Heo <htejun@gmail.com> - 2016-06-16 21:40 +0200
      Re: [PATCH 1/2] workqueue: Move wq_update_unbound_numa() to the  beginning of CPU_ONLINE Gautham R Shenoy <ego@linux.vnet.ibm.com> - 2016-06-21 16:20 +0200
        Re: [PATCH 1/2] workqueue: Move wq_update_unbound_numa() to the  beginning of CPU_ONLINE Tejun Heo <htejun@gmail.com> - 2016-06-21 17:40 +0200
          Re: [PATCH 1/2] workqueue: Move wq_update_unbound_numa() to the  beginning of CPU_ONLINE Tejun Heo <htejun@gmail.com> - 2016-06-21 21:50 +0200
            Re: [PATCH 1/2] workqueue: Move wq_update_unbound_numa() to the  beginning of CPU_ONLINE Peter Zijlstra <peterz@infradead.org> - 2016-06-21 21:50 +0200
              Re: [PATCH 1/2] workqueue: Move wq_update_unbound_numa() to the  beginning of CPU_ONLINE Gautham R Shenoy <ego@linux.vnet.ibm.com> - 2016-06-22 07:20 +0200
          Re: [PATCH 1/2] workqueue: Move wq_update_unbound_numa() to the  beginning of CPU_ONLINE Peter Zijlstra <peterz@infradead.org> - 2016-06-21 22:50 +0200

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