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Date: Tue, 17 Nov 2015 20:15:06 +0100 (CET)
From: Thomas Gleixner <tglx@linutronix.de>
To: Stefan Priebe - Profihost AG <s.priebe@profihost.ag>
cc: linux-netdev@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: Asterisk deadlocks since Kernel 4.1
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On Tue, 17 Nov 2015, Stefan Priebe - Profihost AG wrote:
> since Upgrading our Asterisk System from Kernel 3.18.17 to 4.1.13 it
> deadlocks every few hours (kill -9 is the only thing working). Booting
> with 3.18 again let it run smooth again.
> 
> An strace shows asterisk is looping like this:
> 
> [pid  6068] timerfd_gettime(8, , {it_interval={0, 20000000},
> it_value={0, 140592906050976}}) = 0
> [pid  6068] read(8, "\1\0\0\0\0\0\0\0", 8) = 8
> [pid  6068] poll([{fd=9, events=POLLIN}, {fd=8, events=POLLIN|POLLPRI}],
> 2, 1000) = 1 ([{fd=8, revents=POLLIN}])
> [pid  6068] timerfd_gettime(8, , {it_interval={0, 20000000},
> it_value={0, 140592906050976}}) = 0
> [pid  6068] read(8, "\1\0\0\0\0\0\0\0", 8) = 8
> 
> fd 8 is:
> 
> lrwx------ 1 root root 64 Nov 17 15:27 /proc/6025/fd/8 ->
> anon_inode:[timerfd]
> 
> 
> # cat /proc/6025/stack
> [<ffffffff941d60e9>] poll_schedule_timeout+0x49/0x70
> [<ffffffff941d76c7>] do_sys_poll+0x3d7/0x590
> [<ffffffff941d78bc>] do_restart_poll+0x3c/0x70
> [<ffffffff9408e7ff>] sys_restart_syscall+0x1f/0x30
> [<ffffffff9463f1ee>] system_call_fastpath+0x12/0x71
> [<ffffffffffffffff>] 0xffffffffffffffff
> 
> Any ideas how to debug this?

fd 8 is probably not really interesting. That looks like a interval
timer firing periodically. So it probably waits for fd 9 ...

Thanks,

	tglx