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Re: namespace: deadlock in dec_pid_namespaces

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On 20.01.2017 20:05, Eric W. Biederman wrote:
> Nikolay Borisov <n.borisov.lkml@gmail.com> writes:
> 
>> On 20.01.2017 15:07, Dmitry Vyukov wrote:
>>> Hello,
>>>
>>> I've got the following deadlock report while running syzkaller fuzzer
>>> on eec0d3d065bfcdf9cd5f56dd2a36b94d12d32297 of linux-next (on odroid
>>> device if it matters):
> 
> I am puzzled I thought we had fixed this with:
>   add7c65ca426 ("pid: fix lockdep deadlock warning due to ucount_lock")
> But apparently not.  We  just moved it from hardirq to softirq context.  Bah.
> 
> Thank you very much for the report.
> 
> Nikolay can you make your change use spinlock_irq?  And have put_ucounts
> do spin_lock_irqsave?  That way we just don't care where we call this.

Like the one attached? I haven't really taken careful look as to whether
the function where _irq versions do fiddle with irq state, since this
might cause a problem if we unconditionally enable them.

> 
> I a tired of being clever.
> 
> Eric
> 
> 

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namespace: deadlock in dec_pid_namespaces Dmitry Vyukov <dvyukov@google.com> - 2017-01-20 14:10 +0100
  Re: namespace: deadlock in dec_pid_namespaces Nikolay Borisov <n.borisov.lkml@gmail.com> - 2017-01-20 14:30 +0100
    Re: namespace: deadlock in dec_pid_namespaces ebiederm@xmission.com (Eric W. Biederman) - 2017-01-20 19:20 +0100
      Re: namespace: deadlock in dec_pid_namespaces Nikolay Borisov <n.borisov.lkml@gmail.com> - 2017-01-20 23:50 +0100
        Re: namespace: deadlock in dec_pid_namespaces ebiederm@xmission.com (Eric W. Biederman) - 2017-01-21 01:40 +0100
          Re: namespace: deadlock in dec_pid_namespaces Dmitry Vyukov <dvyukov@google.com> - 2017-01-23 10:40 +0100

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