Date:	Thu, 8 Oct 2015 18:56:52 +0200
From:	Christoph Biedl <linux-kernel.bfrz@...chmal.in-ulm.de>
To:	Eric Dumazet <edumazet@...gle.com>
Cc:	Holger Hoffstätte 
	<holger.hoffstaette@...glemail.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	LKML <linux-kernel@...r.kernel.org>, stable@...r.kernel.org
Subject: Re: Soft lockup issue in Linux 4.1.9

Eric Dumazet wrote...

[ commit 83fccfc3940c4a2db90fd7e7079f5b465cd8c6af ]

> It definitely should help !

Yesterday, I've experienced issues somewhat similar to this, but I'm
not entirely sure:

Four of five systems running 4.1.9 stopped working. No reaction on
network, keyboard, serial console. In one case, the stack trace as
below made it to the loghost.

Two things are quite different. First, the systems had a reasonable
uptime, about a week.

And second, the scary part: All incidents happened within a rather
short time span of three minutes the most, beginning after 16:41:28 and
before 16:41:54 UTC. So I assumed a brownout first - until I realized
the systems faded away at slightly different times, and one is at a
different location. While other systems using different kernel versions
continued to operate on both sites.

So, I'd be glad for answers for

- Is this the same issue or should I be even more afraid?
- What might be the reason for this temporal coincidence? I have no
  plausible idea.

Confused,
    Christoph


 INFO: rcu_sched self-detected stall on CPU { 3}  (t=6000 jiffies g=8932806 c=8932805 q=58491)
 rcu_sched kthread starved for 5999 jiffies!
 Task dump for CPU 3:
 swapper/3       R  running task        0     0      1 0x00000008
  ffffffff81e396c0 ffff88042dcc3b20 ffffffff810807da 0000000000000003
  ffffffff81e396c0 ffff88042dcc3b40 ffffffff81083b78 ffff88042dcc3b80
  0000000000000003 ffff88042dcc3b70 ffffffff810a945c ffff88042dcd5740
 Call Trace:
  <IRQ>  [<ffffffff810807da>] sched_show_task+0xaa/0x110
  [<ffffffff81083b78>] dump_cpu_task+0x38/0x40
  [<ffffffff810a945c>] rcu_dump_cpu_stacks+0x8c/0xc0
  [<ffffffff810abf31>] rcu_check_callbacks+0x3b1/0x680
  [<ffffffff810e7bb7>] ? acct_account_cputime+0x17/0x20
  [<ffffffff8108484e>] ? account_system_time+0x8e/0x180
  [<ffffffff810ae4d3>] update_process_times+0x33/0x60
  [<ffffffff810bcae0>] tick_sched_handle.isra.14+0x30/0x40
  [<ffffffff810bcbd3>] tick_sched_timer+0x43/0x80
  [<ffffffff810aea2a>] __run_hrtimer.isra.32+0x4a/0xd0
  [<ffffffff810af225>] hrtimer_interrupt+0xd5/0x1f0
  [<ffffffff81034d84>] local_apic_timer_interrupt+0x34/0x60
 INFO: rcu_sched self-detected stall on CPU { 3}  (t=6000 jiffies g=8932806 c=8932805 q=58491)
 rcu_sched kthread starved for 5999 jiffies!
 Task dump for CPU 3:
 swapper/3       R  running task        0     0      1 0x00000008
  ffffffff81e396c0 ffff88042dcc3b20 ffffffff810807da 0000000000000003
  ffffffff81e396c0 ffff88042dcc3b40 ffffffff81083b78 ffff88042dcc3b80
  0000000000000003 ffff88042dcc3b70 ffffffff810a945c ffff88042dcd5740
 Call Trace:
  <IRQ>  [<ffffffff810807da>] sched_show_task+0xaa/0x110
  [<ffffffff81083b78>] dump_cpu_task+0x38/0x40
  [<ffffffff8103516c>] smp_apic_timer_interrupt+0x3c/0x60
  [<ffffffff8190db7b>] apic_timer_interrupt+0x6b/0x70
  [<ffffffff8190c8a9>] ? _raw_spin_unlock_irqrestore+0x9/0x10
  [<ffffffff810ade58>] try_to_del_timer_sync+0x48/0x60
  [<ffffffff810adeb2>] ? del_timer_sync+0x42/0x60
  [<ffffffff810adeba>] del_timer_sync+0x4a/0x60
  [<ffffffff8178b7da>] inet_csk_reqsk_queue_drop+0x7a/0x1f0
  [<ffffffff8178ba7f>] reqsk_timer_handler+0x12f/0x290
  [<ffffffff8178b950>] ? inet_csk_reqsk_queue_drop+0x1f0/0x1f0
  [<ffffffff810ad9e6>] call_timer_fn.isra.26+0x26/0x80
  [<ffffffff810a945c>] rcu_dump_cpu_stacks+0x8c/0xc0
  [<ffffffff810abf31>] rcu_check_callbacks+0x3b1/0x680
  [<ffffffff810e7bb7>] ? acct_account_cputime+0x17/0x20
  [<ffffffff8108484e>] ? account_system_time+0x8e/0x180
  [<ffffffff810ae4d3>] update_process_times+0x33/0x60
  [<ffffffff810bcae0>] tick_sched_handle.isra.14+0x30/0x40
  [<ffffffff810bcbd3>] tick_sched_timer+0x43/0x80
  [<ffffffff810aea2a>] __run_hrtimer.isra.32+0x4a/0xd0
  [<ffffffff810af225>] hrtimer_interrupt+0xd5/0x1f0
  [<ffffffff81034d84>] local_apic_timer_interrupt+0x34/0x60
  [<ffffffff810ae1ae>] run_timer_softirq+0x18e/0x220
  [<ffffffff81060b1a>] __do_softirq+0xda/0x1f0
  [<ffffffff81060e16>] irq_exit+0x76/0xa0
  [<ffffffff81035175>] smp_apic_timer_interrupt+0x45/0x60
  [<ffffffff8190db7b>] apic_timer_interrupt+0x6b/0x70
  <EOI>  [<ffffffff810844be>] ? sched_clock_cpu+0x9e/0xb0
  [<ffffffff8100bc15>] ? amd_e400_idle+0x35/0xd0
  [<ffffffff8100bc13>] ? amd_e400_idle+0x33/0xd0
  [<ffffffff8100c42a>] arch_cpu_idle+0xa/0x10
  [<ffffffff810929e3>] cpu_startup_entry+0x2c3/0x330
  [<ffffffff8103516c>] smp_apic_timer_interrupt+0x3c/0x60
  [<ffffffff8190db7b>] apic_timer_interrupt+0x6b/0x70
  [<ffffffff8190c8a9>] ? _raw_spin_unlock_irqrestore+0x9/0x10
  [<ffffffff810ade58>] try_to_del_timer_sync+0x48/0x60
  [<ffffffff810adeb2>] ? del_timer_sync+0x42/0x60
  [<ffffffff810adeba>] del_timer_sync+0x4a/0x60
  [<ffffffff8178b7da>] inet_csk_reqsk_queue_drop+0x7a/0x1f0
  [<ffffffff8178ba7f>] reqsk_timer_handler+0x12f/0x290
  [<ffffffff8178b950>] ? inet_csk_reqsk_queue_drop+0x1f0/0x1f0
  [<ffffffff810ad9e6>] call_timer_fn.isra.26+0x26/0x80
  [<ffffffff810332dc>] start_secondary+0x17c/0x1a0
  [<ffffffff810ae1ae>] run_timer_softirq+0x18e/0x220
  [<ffffffff81060b1a>] __do_softirq+0xda/0x1f0
  [<ffffffff81060e16>] irq_exit+0x76/0xa0
  [<ffffffff81035175>] smp_apic_timer_interrupt+0x45/0x60
  [<ffffffff8190db7b>] apic_timer_interrupt+0x6b/0x70
  <EOI>  [<ffffffff810844be>] ? sched_clock_cpu+0x9e/0xb0
  [<ffffffff8100bc15>] ? amd_e400_idle+0x35/0xd0
  [<ffffffff8100bc13>] ? amd_e400_idle+0x33/0xd0
  [<ffffffff8100c42a>] arch_cpu_idle+0xa/0x10
  [<ffffffff810929e3>] cpu_startup_entry+0x2c3/0x330
  [<ffffffff810332dc>] start_secondary+0x17c/0x1a0

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