Re: rcu_preempt self-detected stall on CPU from 4.5-rc3, since 3.17

From: Paul E. McKenney
Date: Wed Mar 23 2016 - 14:21:15 EST

On Wed, Mar 23, 2016 at 05:15:11PM +0000, Chatre, Reinette wrote:
> Hi Paul,
>
> On 2016-03-22, Paul E. McKenney wrote:
> > On Tue, Mar 22, 2016 at 09:04:47PM +0000, Chatre, Reinette wrote:
> >> On 2016-03-22, Paul E. McKenney wrote:
> >>> You set CONFIG_RCU_CPU_STALL_TIMEOUT=60, which matches the 60004
> >>> jiffies above. Is that value due to a distro setting or something?
> >>> Mainline uses CONFIG_RCU_CPU_STALL_TIMEOUT=21.
> >>
> >> Indeed ... this value originated from a Fedora configuration.
> >
> > OK. Setting it shorter might (or might not) make it reproduce more
> > quickly. This can be set at boot time via rcupdate.rcu_cpu_stall_timeout.
> > Or at compile time via CONFIG_RCU_CPU_STALL_TIMEOUT.
>
> I kept the original configuration and seem to be able to reproduce with that.
>
>
> >>> If dumping manually shortly after the stall is at all non-trivial
> >>> (for example, if your reproduction time is many minute or hours),
> >>> I can supply some patches that automate this. Or you can pick
> >>> them up from -rcu:
> >>
> >> ... could you please point me to the patches you refer to? Or would you like
> > me to try with the entire kernel from rcu/dev?
> >
> > 2dc92e2a86b9 (rcu: Awaken grace-period kthread if too long since FQS)
> > c3fd2095d015 (rcu: Dump ftrace buffer when kicking grace-period kthread)
> >
> > There might be other dependencies, but these are the two that you need.
>
> I did not look closely at the patches when I applied them and because
> of that missed that they need a kernel parameter to be activated. After
> leaving the system idle overnight with these patches the stalls occurred
> but without the parameter I did not capture the data you need. I will
> try again tonight. Below are the traces from last night just in case
> they have value to you.

I know that feeling!

Please boot with the following parameters:

rcu_tree.rcu_kick_kthreads ftrace trace_event=sched_waking,sched_wakeup,sched_wake_idle_without_ipi

Or was this run with tracing? If so, less than three hours isn't too bad.

> [10154.635318] INFO: rcu_preempt detected stalls on CPUs/tasks:
> [10154.639218] 1-...: (0 ticks this GP) idle=c4e/0/0 softirq=99936/99936 fqs=0
> [10154.643497] (detected by 0, t=60005 jiffies, g=24190, c=24189, q=79)
> [10154.647596] Task dump for CPU 1:
> [10154.650818] swapper/1 R running task 0 0 1 0x00200000
> [10154.655052] 00002656bf74de5e ffff8801785cfed0 ffffffff818af34c ffff880100000000
> [10154.659349] 0000000600000003 ffff8801785d0000 ffff880072f0bc00 ffffffff822dcf80
> [10154.663636] ffff8801785cc000 ffff8801785cc000 ffff8801785cfee0 ffffffff818af597
> [10154.667916] Call Trace:
> [10154.670845] [<ffffffff818af34c>] ? cpuidle_enter_state+0xfc/0x310
> [10154.674802] [<ffffffff818af597>] ? cpuidle_enter+0x17/0x20
> [10154.678564] [<ffffffff811515ba>] ? call_cpuidle+0x2a/0x40
> [10154.682295] [<ffffffff8115198d>] ? cpu_startup_entry+0x28d/0x360
> [10154.686187] [<ffffffff8108c864>] ? start_secondary+0x114/0x140
> [10154.690040] rcu_preempt kthread starved for 60005 jiffies! g24190 c24189 f0x0 RCU_GP_WAIT_FQS(3) ->state=0x1

Still the same type of failure, which is reassuring.

Thanx, Paul

> [10154.694944] rcu_preempt S ffff8801785b7d68 0 7 2 0x00000000
> [10154.699062] ffff8801785b7d68 ffff88017dc8cc80 ffff8801785c3b80 ffff8801785abb80
> [10154.703275] ffff8801785b8000 ffff8801785b7da0 ffff88017dc8cc80 ffff88017dc8cc80
> [10154.707481] 0000000000000003 ffff8801785b7d80 ffffffff81ab03df 00000001027e21aa
> [10154.711692] Call Trace:
> [10154.714548] [<ffffffff81ab03df>] schedule+0x3f/0xa0
> [10154.718075] [<ffffffff81ab4397>] schedule_timeout+0x127/0x270
> [10154.721832] [<ffffffff81171a00>] ? detach_if_pending+0x120/0x120
> [10154.725659] [<ffffffff8116d983>] rcu_gp_kthread+0x6d3/0xa40
> [10154.729379] [<ffffffff811513a0>] ? wake_atomic_t_function+0x70/0x70
> [10154.733235] [<ffffffff8116d2b0>] ? force_qs_rnp+0x1b0/0x1b0
> [10154.736854] [<ffffffff8112f856>] kthread+0xe6/0x100
> [10154.740267] [<ffffffff8112f770>] ? kthread_worker_fn+0x190/0x190
> [10154.743980] [<ffffffff81ab5ccf>] ret_from_fork+0x3f/0x70
> [10154.747511] [<ffffffff8112f770>] ? kthread_worker_fn+0x190/0x190
> [11348.912706] INFO: rcu_preempt detected stalls on CPUs/tasks:
> [11348.916346] 2-...: (0 ticks this GP) idle=586/0/0 softirq=133504/133504 fqs=0
> [11348.920407] (detected by 3, t=60002 jiffies, g=26799, c=26798, q=72)
> [11348.924244] Task dump for CPU 2:
> [11348.927205] swapper/2 R running task 0 0 1 0x00200000
> [11348.931178] 00002adc83427a76 ffff8801785d3ed0 ffffffff818af34c ffff880100000000
> [11348.935217] 0000000600000003 ffff8801785d4000 ffff880177d01e00 ffffffff822dcf80
> [11348.939237] ffff8801785d0000 ffff8801785d0000 ffff8801785d3ee0 ffffffff818af597
> [11348.943252] Call Trace:
> [11348.945921] [<ffffffff818af34c>] ? cpuidle_enter_state+0xfc/0x310
> [11348.949615] [<ffffffff818af597>] ? cpuidle_enter+0x17/0x20
> [11348.953115] [<ffffffff811515ba>] ? call_cpuidle+0x2a/0x40
> [11348.956584] [<ffffffff8115198d>] ? cpu_startup_entry+0x28d/0x360
> [11348.960215] [<ffffffff8108c864>] ? start_secondary+0x114/0x140
> [11348.963808] rcu_preempt kthread starved for 60002 jiffies! g26799 c26798 f0x0 RCU_GP_WAIT_FQS(3) ->state=0x1
> [11348.968452] rcu_preempt S ffff8801785b7d68 0 7 2 0x00000000
> [11348.972309] ffff8801785b7d68 ffff88017dd0cc80 ffff8801785c5940 ffff8801785abb80
> [11348.976266] ffff8801785b8000 ffff8801785b7da0 ffff88017dd0cc80 ffff88017dd0cc80
> [11348.980207] 0000000000000003 ffff8801785b7d80 ffffffff81ab03df 0000000102c9d45e
> [11348.984142] Call Trace:
> [11348.986714] [<ffffffff81ab03df>] schedule+0x3f/0xa0
> [11348.989974] [<ffffffff81ab4397>] schedule_timeout+0x127/0x270
> [11348.993453] [<ffffffff81171a00>] ? detach_if_pending+0x120/0x120
> [11348.997000] [<ffffffff8116d983>] rcu_gp_kthread+0x6d3/0xa40
> [11349.000431] [<ffffffff811513a0>] ? wake_atomic_t_function+0x70/0x70
> [11349.004040] [<ffffffff8116d2b0>] ? force_qs_rnp+0x1b0/0x1b0
> [11349.007449] [<ffffffff8112f856>] kthread+0xe6/0x100
> [11349.010676] [<ffffffff8112f770>] ? kthread_worker_fn+0x190/0x190
> [11349.014216] [<ffffffff81ab5ccf>] ret_from_fork+0x3f/0x70
> [11349.017568] [<ffffffff8112f770>] ? kthread_worker_fn+0x190/0x190
> [11790.539207] INFO: rcu_preempt detected stalls on CPUs/tasks:
> [11790.542652] 2-...: (0 ticks this GP) idle=944/0/0 softirq=133668/133668 fqs=0
> [11790.546505] (detected by 3, t=60003 jiffies, g=27589, c=27588, q=72)
> [11790.550124] Task dump for CPU 2:
> [11790.552871] swapper/2 R running task 0 0 1 0x00200000
> [11790.556678] 00002c8422fed65e ffff8801785d3ed0 ffffffff818af34c ffff880100000000
> [11790.560580] 0000000600000003 ffff8801785d4000 ffff880177d01e00 ffffffff822dcf80
> [11790.564485] ffff8801785d0000 ffff8801785d0000 ffff8801785d3ee0 ffffffff818af597
> [11790.568389] Call Trace:
> [11790.570942] [<ffffffff818af34c>] ? cpuidle_enter_state+0xfc/0x310
> [11790.574525] [<ffffffff818af597>] ? cpuidle_enter+0x17/0x20
> [11790.577934] [<ffffffff811515ba>] ? call_cpuidle+0x2a/0x40
> [11790.581311] [<ffffffff8115198d>] ? cpu_startup_entry+0x28d/0x360
> [11790.584853] [<ffffffff8108c864>] ? start_secondary+0x114/0x140
> [11790.588350] rcu_preempt kthread starved for 60003 jiffies! g27589 c27588 f0x0 RCU_GP_WAIT_FQS(3) ->state=0x1
> [11790.592945] rcu_preempt S ffff8801785b7d68 0 7 2 0x00000000
> [11790.596808] ffff8801785b7d68 ffff88017dd0cc80 ffff8801785c5940 ffff8801785abb80
> [11790.600751] ffff8801785b8000 ffff8801785b7da0 ffff88017dd0cc80 ffff88017dd0cc80
> [11790.604688] 0000000000000003 ffff8801785b7d80 ffffffff81ab03df 0000000102e5d253
> [11790.608635] Call Trace:
> [11790.611220] [<ffffffff81ab03df>] schedule+0x3f/0xa0
> [11790.614480] [<ffffffff81ab4397>] schedule_timeout+0x127/0x270
> [11790.617971] [<ffffffff81171a00>] ? detach_if_pending+0x120/0x120
> [11790.621530] [<ffffffff8116d983>] rcu_gp_kthread+0x6d3/0xa40
> [11790.624972] [<ffffffff811513a0>] ? wake_atomic_t_function+0x70/0x70
> [11790.628558] [<ffffffff8116d2b0>] ? force_qs_rnp+0x1b0/0x1b0
> [11790.631904] [<ffffffff8112f856>] kthread+0xe6/0x100
> [11790.635043] [<ffffffff8112f770>] ? kthread_worker_fn+0x190/0x190
> [11790.638485] [<ffffffff81ab5ccf>] ret_from_fork+0x3f/0x70
> [11790.641745] [<ffffffff8112f770>] ? kthread_worker_fn+0x190/0x190
> [11820.319166] INFO: rcu_preempt detected stalls on CPUs/tasks:
> [11820.322523] 2-...: (0 ticks this GP) idle=9b4/0/0 softirq=133674/133674 fqs=0
> [11820.326301] (detected by 3, t=60002 jiffies, g=27620, c=27619, q=64)
> [11820.329856] Task dump for CPU 2:
> [11820.332536] swapper/2 R running task 0 0 1 0x00200000
> [11820.336228] 00002ca4dc6b2bb1 ffff8801785d3ed0 ffffffff818af34c ffff880100000000
> [11820.339990] 0000000600000003 ffff8801785d4000 ffff880177d01e00 ffffffff822dcf80
> [11820.343749] ffff8801785d0000 ffff8801785d0000 ffff8801785d3ee0 ffffffff818af597
> [11820.347483] Call Trace:
> [11820.349852] [<ffffffff818af34c>] ? cpuidle_enter_state+0xfc/0x310
> [11820.353250] [<ffffffff818af597>] ? cpuidle_enter+0x17/0x20
> [11820.356463] [<ffffffff811515ba>] ? call_cpuidle+0x2a/0x40
> [11820.359637] [<ffffffff8115198d>] ? cpu_startup_entry+0x28d/0x360
> [11820.362973] [<ffffffff8108c864>] ? start_secondary+0x114/0x140
> [11820.366264] rcu_preempt kthread starved for 60002 jiffies! g27620 c27619 f0x0 RCU_GP_WAIT_FQS(3) ->state=0x1
> [11820.370643] rcu_preempt S ffff8801785b7d68 0 7 2 0x00000000
> [11820.374276] ffff8801785b7d68 ffff88017dd0cc80 ffff8801785c5940 ffff8801785abb80
> [11820.378026] ffff8801785b8000 ffff8801785b7da0 ffff88017dd0cc80 ffff88017dd0cc80
> [11820.381775] 0000000000000003 ffff8801785b7d80 ffffffff81ab03df 0000000102e7b58c
> [11820.385537] Call Trace:
> [11820.387940] [<ffffffff81ab03df>] schedule+0x3f/0xa0
> [11820.391005] [<ffffffff81ab4397>] schedule_timeout+0x127/0x270
> [11820.394286] [<ffffffff81171a00>] ? detach_if_pending+0x120/0x120
> [11820.397626] [<ffffffff8116d983>] rcu_gp_kthread+0x6d3/0xa40
> [11820.400853] [<ffffffff811513a0>] ? wake_atomic_t_function+0x70/0x70
> [11820.404269] [<ffffffff8116d2b0>] ? force_qs_rnp+0x1b0/0x1b0
> [11820.407478] [<ffffffff8112f856>] kthread+0xe6/0x100
> [11820.410493] [<ffffffff8112f770>] ? kthread_worker_fn+0x190/0x190
> [11820.413824] [<ffffffff81ab5ccf>] ret_from_fork+0x3f/0x70
> [11820.416966] [<ffffffff8112f770>] ? kthread_worker_fn+0x190/0x190
> [11903.292474] INFO: rcu_preempt detected stalls on CPUs/tasks:
> [11903.295736] 2-...: (0 ticks this GP) idle=bd2/0/0 softirq=133700/133700 fqs=0
> [11903.299427] (detected by 3, t=60003 jiffies, g=27759, c=27758, q=277)
> [11903.302921] Task dump for CPU 2:
> [11903.305513] swapper/2 R running task 0 0 1 0x00200000
> [11903.309164] 00002cf65a063204 ffff8801785d3ed0 ffffffff818af34c ffff880100000000
> [11903.312931] 0000000600000003 ffff8801785d4000 ffff880177d01e00 ffffffff822dcf80
> [11903.316685] ffff8801785d0000 ffff8801785d0000 ffff8801785d3ee0 ffffffff818af597
> [11903.320426] Call Trace:
> [11903.322802] [<ffffffff818af34c>] ? cpuidle_enter_state+0xfc/0x310
> [11903.326199] [<ffffffff818af597>] ? cpuidle_enter+0x17/0x20
> [11903.329416] [<ffffffff811515ba>] ? call_cpuidle+0x2a/0x40
> [11903.332591] [<ffffffff8115198d>] ? cpu_startup_entry+0x28d/0x360
> [11903.335931] [<ffffffff8108c864>] ? start_secondary+0x114/0x140
> [11903.339226] rcu_preempt kthread starved for 60003 jiffies! g27759 c27758 f0x0 RCU_GP_WAIT_FQS(3) ->state=0x1
> [11903.343607] rcu_preempt S ffff8801785b7d68 0 7 2 0x00000000
> [11903.347246] ffff8801785b7d68 ffff88017dd0cc80 ffff8801785c5940 ffff8801785abb80
> [11903.350999] ffff8801785b8000 ffff8801785b7da0 ffff88017dd0cc80 ffff88017dd0cc80
> [11903.354750] 0000000000000003 ffff8801785b7d80 ffffffff81ab03df 0000000102ecf7e4
> [11903.358508] Call Trace:
> [11903.360909] [<ffffffff81ab03df>] schedule+0x3f/0xa0
> [11903.363979] [<ffffffff81ab4397>] schedule_timeout+0x127/0x270
> [11903.367259] [<ffffffff81171a00>] ? detach_if_pending+0x120/0x120
> [11903.370601] [<ffffffff8116d983>] rcu_gp_kthread+0x6d3/0xa40
> [11903.373829] [<ffffffff811513a0>] ? wake_atomic_t_function+0x70/0x70
> [11903.377243] [<ffffffff8116d2b0>] ? force_qs_rnp+0x1b0/0x1b0
> [11903.380455] [<ffffffff8112f856>] kthread+0xe6/0x100
> [11903.383473] [<ffffffff8112f770>] ? kthread_worker_fn+0x190/0x190
> [11903.386804] [<ffffffff81ab5ccf>] ret_from_fork+0x3f/0x70
> [11903.389942] [<ffffffff8112f770>] ? kthread_worker_fn+0x190/0x190
> [12101.322638] INFO: rcu_preempt detected stalls on CPUs/tasks:
> [12101.325902] 2-...: (19 GPs behind) idle=880/0/0 softirq=133768/133768 fqs=1
> [12101.329542] (detected by 1, t=60004 jiffies, g=28170, c=28169, q=41)
> [12101.333009] Task dump for CPU 2:
> [12101.335599] swapper/2 R running task 0 0 1 0x00200000
> [12101.339248] 00002db4171b61e1 ffff8801785d3ed0 ffffffff818af34c ffff880100000000
> [12101.343008] 0000000600000003 ffff8801785d4000 ffff880177d01e00 ffffffff822dcf80
> [12101.346763] ffff8801785d0000 ffff8801785d0000 ffff8801785d3ee0 ffffffff818af597
> [12101.350501] Call Trace:
> [12101.352868] [<ffffffff818af34c>] ? cpuidle_enter_state+0xfc/0x310
> [12101.356262] [<ffffffff818af597>] ? cpuidle_enter+0x17/0x20
> [12101.359475] [<ffffffff811515ba>] ? call_cpuidle+0x2a/0x40
> [12101.362645] [<ffffffff8115198d>] ? cpu_startup_entry+0x28d/0x360
> [12101.365980] [<ffffffff8108c864>] ? start_secondary+0x114/0x140
> [12101.369270] rcu_preempt kthread starved for 60000 jiffies! g28170 c28169 f0x0 RCU_GP_WAIT_FQS(3) ->state=0x1
> [12101.373646] rcu_preempt S ffff8801785b7d68 0 7 2 0x00000000
> [12101.377281] ffff8801785b7d68 ffff88017dd0cc80 ffff8801785c5940 ffff8801785abb80
> [12101.381030] ffff8801785b8000 ffff8801785b7da0 ffff88017dd0cc80 ffff88017dd0cc80
> [12101.384778] 0000000000000003 ffff8801785b7d80 ffffffff81ab03df 0000000102f98533
> [12101.388532] Call Trace:
> [12101.390927] [<ffffffff81ab03df>] schedule+0x3f/0xa0
> [12101.393991] [<ffffffff81ab4397>] schedule_timeout+0x127/0x270
> [12101.397266] [<ffffffff81171a00>] ? detach_if_pending+0x120/0x120
> [12101.400602] [<ffffffff8116d983>] rcu_gp_kthread+0x6d3/0xa40
> [12101.403825] [<ffffffff811513a0>] ? wake_atomic_t_function+0x70/0x70
> [12101.407240] [<ffffffff8116d2b0>] ? force_qs_rnp+0x1b0/0x1b0
> [12101.410450] [<ffffffff8112f856>] kthread+0xe6/0x100
> [12101.413465] [<ffffffff8112f770>] ? kthread_worker_fn+0x190/0x190
> [12101.416793] [<ffffffff81ab5ccf>] ret_from_fork+0x3f/0x70
> [12101.419930] [<ffffffff8112f770>] ? kthread_worker_fn+0x190/0x190
> [12269.411058] INFO: rcu_preempt detected stalls on CPUs/tasks:
> [12269.414316] 2-...: (27 GPs behind) idle=daa/0/0 softirq=133902/133902 fqs=1
> [12269.417947] (detected by 0, t=60003 jiffies, g=28504, c=28503, q=347)
> [12269.421426] Task dump for CPU 2:
> [12269.424012] swapper/2 R running task 0 0 1 0x00200000
> [12269.427656] 00002e58b5f8d033 ffff8801785d3ed0 ffffffff818af34c ffff880100000000
> [12269.431405] 0000000600000003 ffff8801785d4000 ffff880177d01e00 ffffffff822dcf80
> [12269.435153] ffff8801785d0000 ffff8801785d0000 ffff8801785d3ee0 ffffffff818af597
> [12269.438886] Call Trace:
> [12269.441252] [<ffffffff818af34c>] ? cpuidle_enter_state+0xfc/0x310
> [12269.444638] [<ffffffff818af597>] ? cpuidle_enter+0x17/0x20
> [12269.447850] [<ffffffff811515ba>] ? call_cpuidle+0x2a/0x40
> [12269.451014] [<ffffffff8115198d>] ? cpu_startup_entry+0x28d/0x360
> [12269.454348] [<ffffffff8108c864>] ? start_secondary+0x114/0x140
> [12269.457634] rcu_preempt kthread starved for 59872 jiffies! g28504 c28503 f0x0 RCU_GP_WAIT_FQS(3) ->state=0x1
> [12269.462008] rcu_preempt S ffff8801785b7d68 0 7 2 0x00000000
> [12269.465636] ffff8801785b7d68 ffff88017dd0cc80 ffff8801785c5940 ffff8801785abb80
> [12269.469380] ffff8801785b8000 ffff8801785b7da0 ffff88017dd0cc80 ffff88017dd0cc80
> [12269.473121] 0000000000000003 ffff8801785b7d80 ffffffff81ab03df 0000000103042d26
> [12269.476868] Call Trace:
> [12269.479262] [<ffffffff81ab03df>] schedule+0x3f/0xa0
> [12269.482321] [<ffffffff81ab4397>] schedule_timeout+0x127/0x270
> [12269.485592] [<ffffffff81171a00>] ? detach_if_pending+0x120/0x120
> [12269.488926] [<ffffffff8116d983>] rcu_gp_kthread+0x6d3/0xa40
> [12269.492144] [<ffffffff811513a0>] ? wake_atomic_t_function+0x70/0x70
> [12269.495554] [<ffffffff8116d2b0>] ? force_qs_rnp+0x1b0/0x1b0
> [12269.498756] [<ffffffff8112f856>] kthread+0xe6/0x100
> [12269.501764] [<ffffffff8112f770>] ? kthread_worker_fn+0x190/0x190
> [12269.505090] [<ffffffff81ab5ccf>] ret_from_fork+0x3f/0x70
> [12269.508224] [<ffffffff8112f770>] ? kthread_worker_fn+0x190/0x190
> [12426.587923] INFO: rcu_preempt detected stalls on CPUs/tasks:
> [12426.591181] 2-...: (17 GPs behind) idle=15c/0/0 softirq=134033/134034 fqs=1
> [12426.594815] (detected by 0, t=60002 jiffies, g=28804, c=28803, q=396)
> [12426.598296] Task dump for CPU 2:
> [12426.600881] swapper/2 R running task 0 0 1 0x00200000
> [12426.604528] 00002eed4414d5d4 ffff8801785d3ed0 ffffffff818af34c ffff880100000000
> [12426.608284] 0000000600000003 ffff8801785d4000 ffff880177d01e00 ffffffff822dcf80
> [12426.612030] ffff8801785d0000 ffff8801785d0000 ffff8801785d3ee0 ffffffff818af597
> [12426.615762] Call Trace:
> [12426.618131] [<ffffffff818af34c>] ? cpuidle_enter_state+0xfc/0x310
> [12426.621522] [<ffffffff818af597>] ? cpuidle_enter+0x17/0x20
> [12426.624733] [<ffffffff811515ba>] ? call_cpuidle+0x2a/0x40
> [12426.627903] [<ffffffff8115198d>] ? cpu_startup_entry+0x28d/0x360
> [12426.631238] [<ffffffff8108c864>] ? start_secondary+0x114/0x140
> [12426.634527] rcu_preempt kthread starved for 59998 jiffies! g28804 c28803 f0x0 RCU_GP_WAIT_FQS(3) ->state=0x1
> [12426.638900] rcu_preempt S ffff8801785b7d68 0 7 2 0x00000000
> [12426.642535] ffff8801785b7d68 ffff88017dd0cc80 ffff8801785c5940 ffff8801785abb80
> [12426.646285] ffff8801785b8000 ffff8801785b7da0 ffff88017dd0cc80 ffff88017dd0cc80
> [12426.650031] 0000000000000003 ffff8801785b7d80 ffffffff81ab03df 00000001030e230e
> [12426.653787] Call Trace:
> [12426.656186] [<ffffffff81ab03df>] schedule+0x3f/0xa0
> [12426.659251] [<ffffffff81ab4397>] schedule_timeout+0x127/0x270
> [12426.662528] [<ffffffff81171a00>] ? detach_if_pending+0x120/0x120
> [12426.665868] [<ffffffff8116d983>] rcu_gp_kthread+0x6d3/0xa40
> [12426.669091] [<ffffffff811513a0>] ? wake_atomic_t_function+0x70/0x70
> [12426.672502] [<ffffffff8116d2b0>] ? force_qs_rnp+0x1b0/0x1b0
> [12426.675710] [<ffffffff8112f856>] kthread+0xe6/0x100
> [12426.678724] [<ffffffff8112f770>] ? kthread_worker_fn+0x190/0x190
> [12426.682052] [<ffffffff81ab5ccf>] ret_from_fork+0x3f/0x70
> [12426.685188] [<ffffffff8112f770>] ? kthread_worker_fn+0x190/0x190
>
>