Message-ID: <20160323182055.GG4287@linux.vnet.ibm.com>
Date:	Wed, 23 Mar 2016 11:20:55 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	"Chatre, Reinette" <reinette.chatre@...el.com>
Cc:	Jacob Pan <jacob.jun.pan@...ux.intel.com>,
	Josh Triplett <josh@...htriplett.org>,
	Ross Green <rgkernel@...il.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	John Stultz <john.stultz@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	"dipankar@...ibm.com" <dipankar@...ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	rostedt <rostedt@...dmis.org>,
	David Howells <dhowells@...hat.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Darren Hart <dvhart@...ux.intel.com>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	Oleg Nesterov <oleg@...hat.com>,
	pranith kumar <bobby.prani@...il.com>
Subject: Re: rcu_preempt self-detected stall on CPU from 4.5-rc3, since 3.17

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
> 
> 

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