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Re: [PATCH v2] cgroup: disable irqs while holding css_set_lock

From Daniel Bristot de Oliveira <daolivei@redhat.com>
Newsgroups linux.kernel
Subject Re: [PATCH v2] cgroup: disable irqs while holding css_set_lock
Date 2016-06-17 02:20 +0200
Message-ID <rKPFU-7pF-9@gated-at.bofh.it> (permalink)
References (1 earlier) <rHv0Z-6Mo-15@gated-at.bofh.it> <rHvDI-7fg-23@gated-at.bofh.it> <rKNkL-5aq-63@gated-at.bofh.it> <rKNE6-5vQ-5@gated-at.bofh.it> <rKNNL-5z3-1@gated-at.bofh.it>
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On 06/16/2016 07:14 PM, Tejun Heo wrote:
> Except that the patch seems to use irqsave/restore instead of plain
> irq ones in places.  Care to update those?

Hi Tejun,

The use of the irq spin_(un)lock_irq() assumes that the code is always
called with IRQs enabled. But that is not always true in this case, as
we call cgroup_free() in the hard IRQ context, and unconditionally
enable IRQ in this context is a problem. So we need to use irqsave/restore.

Discussing with rostedt, we figured that this needs to be IRQ safe
(using irqsave/restore) in the PREEMPT RT too, so I need to code a v3 of
this patch using raw_spin_*() functions to avoid this problem in the -rt
kernel as well.

Do you see any problems on this?

Thanks! -- Daniel

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Thread

Re: [PATCH v2] cgroup: disable irqs while holding css_set_lock Daniel Bristot de Oliveira <daolivei@redhat.com> - 2016-06-16 23:50 +0200
  Re: [PATCH v2] cgroup: disable irqs while holding css_set_lock Tejun Heo <tj@kernel.org> - 2016-06-17 00:10 +0200
    Re: [PATCH v2] cgroup: disable irqs while holding css_set_lock Tejun Heo <tj@kernel.org> - 2016-06-17 00:20 +0200
      Re: [PATCH v2] cgroup: disable irqs while holding css_set_lock Daniel Bristot de Oliveira <daolivei@redhat.com> - 2016-06-17 02:20 +0200
        Re: [PATCH v2] cgroup: disable irqs while holding css_set_lock Tejun Heo <tj@kernel.org> - 2016-06-17 07:40 +0200
          Re: [PATCH v2] cgroup: disable irqs while holding css_set_lock Daniel Bristot de Oliveira <daolivei@redhat.com> - 2016-06-17 22:00 +0200
            Re: [PATCH v2] cgroup: disable irqs while holding css_set_lock Daniel Bristot de Oliveira <daolivei@redhat.com> - 2016-06-22 22:10 +0200

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