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Date: Mon, 11 Aug 2014 16:09:31 -0400
From: Dave Jones <davej@redhat.com>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
        Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: nohz fail (was: perf related boot hang.)
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On Thu, Aug 07, 2014 at 03:16:49PM +0200, Frederic Weisbecker wrote:
 
 > > >   <<EOE>>  <IRQ>  [<ffffffff8a0ccd2f>] lock_acquired+0xaf/0x450
 > > >   [<ffffffff8a0f74c5>] ? lock_hrtimer_base.isra.20+0x25/0x50
 > > >   [<ffffffff8a7fc678>] _raw_spin_lock_irqsave+0x78/0x90
 > > >   [<ffffffff8a0f74c5>] ? lock_hrtimer_base.isra.20+0x25/0x50
 > > >   [<ffffffff8a0f74c5>] lock_hrtimer_base.isra.20+0x25/0x50
 > > >   [<ffffffff8a0f7723>] hrtimer_try_to_cancel+0x33/0x1e0
 > > >   [<ffffffff8a0f78ea>] hrtimer_cancel+0x1a/0x30
 > > >   [<ffffffff8a109237>] tick_nohz_restart+0x17/0x90
 > > >   [<ffffffff8a10a213>] __tick_nohz_full_check+0xc3/0x100
 > > >   [<ffffffff8a10a25e>] nohz_full_kick_work_func+0xe/0x10
 > > >   [<ffffffff8a17c884>] irq_work_run_list+0x44/0x70
 > > >   [<ffffffff8a17c8da>] irq_work_run+0x2a/0x50
 > > >   [<ffffffff8a0f700b>] update_process_times+0x5b/0x70
 > > >   [<ffffffff8a109005>] tick_sched_handle.isra.21+0x25/0x60
 > > >   [<ffffffff8a109b81>] tick_sched_timer+0x41/0x60
 > > >   [<ffffffff8a0f7aa2>] __run_hrtimer+0x72/0x470
 > > >   [<ffffffff8a109b40>] ? tick_sched_do_timer+0xb0/0xb0
 > > >   [<ffffffff8a0f8707>] hrtimer_interrupt+0x117/0x270
 > > >   [<ffffffff8a034357>] local_apic_timer_interrupt+0x37/0x60
 > > >   [<ffffffff8a80010f>] smp_apic_timer_interrupt+0x3f/0x50
 > > >   [<ffffffff8a7fe52f>] apic_timer_interrupt+0x6f/0x80
 > > 
 > > And that looks like someone trying to cancel a timer from a timer, I
 > > guess that won't work, seeing how cancel will wait for the timer handler
 > > completion etc.
 > > 
 > > This is because of the fallback irq_work_run() in the tick
 > > (update_process_times).
 > > 
 > 
 > Indeed, I saw that too but very rarely.

FWIW, I'm now seeing this quite often (several times a day) when I run
trinity on current git master.

	Dave