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Date: Tue, 31 Oct 2017 11:31:34 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: syzbot 
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Subject: Re: WARNING in get_pi_state
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On Tue, Oct 31, 2017 at 11:18:53AM +0100, Peter Zijlstra wrote:
> On Tue, Oct 31, 2017 at 09:36:44AM +0100, Peter Zijlstra wrote:
> > On Mon, Oct 30, 2017 at 12:44:00PM -0700, syzbot wrote:
> > > WARNING: CPU: 1 PID: 24353 at kernel/futex.c:818 get_pi_state+0x15b/0x190
> > > kernel/futex.c:818
> > 
> > >  exit_pi_state_list+0x556/0x7a0 kernel/futex.c:932
> > >  mm_release+0x46d/0x590 kernel/fork.c:1191
> > >  exit_mm kernel/exit.c:499 [inline]
> > >  do_exit+0x481/0x1b00 kernel/exit.c:852
> > >  SYSC_exit kernel/exit.c:937 [inline]
> > >  SyS_exit+0x22/0x30 kernel/exit.c:935
> > >  entry_SYSCALL_64_fastpath+0x1f/0xbe
> > 
> > 
> > Argh, I definitely messed that up. Let me have a prod..
> 
> The below appears to cure the problem, I could (fairly quickly)
> reproduce the issue one I hacked up the repro.c to not bother with
> tunnels.
> 
> With the below patch, the reproducer has been running for a fairly long
> time now without issue.

And of course, now it went *splat*, lemme continue staring..