Re: 4.2-rc5 rcu stalls.

[Dave Jones]

On Tue, Aug 04, 2015 at 12:54:35AM -0400, Sasha Levin wrote:
 > On 08/03/2015 06:03 PM, Paul E. McKenney wrote:
 > >> > Ugh, that doesn't revert cleanly.  Got something handy ?
 > > I do not, but perhaps either Sasha or Frederic do.
 > 
 > I've attached a revert courtesy of Peter.

Thanks.  At first I thought this was doing the trick, but then I hit this again.


[23643.545873] INFO: rcu_preempt detected stalls on CPUs/tasks:
[23643.546031] 	Tasks blocked on level-0 rcu_node (CPUs 0-3): P31722
[23643.546173] 	(detected by 3, t=65002 jiffies, g=2256887, c=2256886, q=0)
[23643.546326] trinity-watchdo R  running task    14336 31722  31721 0x00080000
[23643.546488]  ffff8804fcfe7cc8 000000000000ded0 0000000000000002 ffff8804f58bb680
[23643.546661]  ffff8800ce4951c0 ffff8804fcfe7cb8 ffff8804fcfe8000 ffff8804f6552608
[23643.546830]  0000000000000009 ffff8804fcfe7e88 0000000000000009 ffff8804fcfe7ce8
[23643.547001] Call Trace:
[23643.547058]  [<ffffffff887fa2b2>] preempt_schedule_common+0x22/0x40
[23643.547201]  [<ffffffff887fa2ef>] preempt_schedule+0x1f/0x30
[23643.547329]  [<ffffffff88001058>] ___preempt_schedule+0x12/0x14
[23643.547465]  [<ffffffff8808b76d>] ? do_send_sig_info+0x5d/0x80
[23643.547599]  [<ffffffff887fff32>] ? _raw_spin_unlock_irqrestore+0x42/0x70
[23643.547753]  [<ffffffff887fff50>] ? _raw_spin_unlock_irqrestore+0x60/0x70
[23643.547910]  [<ffffffff8808b76d>] do_send_sig_info+0x5d/0x80
[23643.548039]  [<ffffffff8808be62>] group_send_sig_info+0xb2/0x120
[23643.548175]  [<ffffffff8808bdb5>] ? group_send_sig_info+0x5/0x120
[23643.548314]  [<ffffffff880ea62f>] ? rcu_read_lock_held+0x4f/0x60
[23643.548451]  [<ffffffff8808c05f>] kill_pid_info+0x7f/0x150
[23643.548576]  [<ffffffff8808c000>] ? kill_pid_info+0x20/0x150
[23643.548705]  [<ffffffff8808c244>] SYSC_kill+0xf4/0x2b0
[23643.548821]  [<ffffffff8808c1ed>] ? SYSC_kill+0x9d/0x2b0
[23643.548942]  [<ffffffff880d35cb>] ? trace_hardirqs_on_caller+0x14b/0x1e0
[23643.549097]  [<ffffffff880d366d>] ? trace_hardirqs_on+0xd/0x10
[23643.549231]  [<ffffffff88192f63>] ? context_tracking_user_exit+0x13/0x20
[23643.549387]  [<ffffffff88012c47>] ? syscall_trace_enter_phase1+0xf7/0x150
[23643.549540]  [<ffffffff88001017>] ? trace_hardirqs_on_thunk+0x17/0x19
[23643.549687]  [<ffffffff8808e64e>] SyS_kill+0xe/0x10
[23643.549799]  [<ffffffff88800997>] entry_SYSCALL_64_fastpath+0x12/0x6f
[23643.549946] trinity-watchdo R  running task    14336 31722  31721 0x00080000
[23643.550106]  ffff8804fcfe7cc8 000000000000ded0 0000000000000002 ffff8804f58bb680
[23643.550276]  ffff8800ce4951c0 ffff8804fcfe7cb8 ffff8804fcfe8000 ffff8804f6552608
[23643.550446]  0000000000000009 ffff8804fcfe7e88 0000000000000009 ffff8804fcfe7ce8
[23643.550615] Call Trace:
[23643.550668]  [<ffffffff887fa2b2>] preempt_schedule_common+0x22/0x40
[23643.550809]  [<ffffffff887fa2ef>] preempt_schedule+0x1f/0x30
[23643.550935]  [<ffffffff88001058>] ___preempt_schedule+0x12/0x14
[23643.551072]  [<ffffffff8808b76d>] ? do_send_sig_info+0x5d/0x80
[23643.551204]  [<ffffffff887fff32>] ? _raw_spin_unlock_irqrestore+0x42/0x70
[23643.551358]  [<ffffffff887fff50>] ? _raw_spin_unlock_irqrestore+0x60/0x70
[23643.551515]  [<ffffffff8808b76d>] do_send_sig_info+0x5d/0x80
[23643.551642]  [<ffffffff8808be62>] group_send_sig_info+0xb2/0x120
[23643.551779]  [<ffffffff8808bdb5>] ? group_send_sig_info+0x5/0x120
[23643.551915]  [<ffffffff880ea62f>] ? rcu_read_lock_held+0x4f/0x60
[23643.557757]  [<ffffffff8808c05f>] kill_pid_info+0x7f/0x150
[23643.563613]  [<ffffffff8808c000>] ? kill_pid_info+0x20/0x150
[23643.569450]  [<ffffffff8808c244>] SYSC_kill+0xf4/0x2b0
[23643.575270]  [<ffffffff8808c1ed>] ? SYSC_kill+0x9d/0x2b0
[23643.581025]  [<ffffffff880d35cb>] ? trace_hardirqs_on_caller+0x14b/0x1e0
[23643.586867]  [<ffffffff880d366d>] ? trace_hardirqs_on+0xd/0x10
[23643.592620]  [<ffffffff88192f63>] ? context_tracking_user_exit+0x13/0x20
[23643.598317]  [<ffffffff88012c47>] ? syscall_trace_enter_phase1+0xf7/0x150
[23643.603903]  [<ffffffff88001017>] ? trace_hardirqs_on_thunk+0x17/0x19
[23643.609404]  [<ffffffff8808e64e>] SyS_kill+0xe/0x10
[23643.614788]  [<ffffffff88800997>] entry_SYSCALL_64_fastpath+0x12/0x6f

	Dave

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