Re: [RCU] kernel hangs in wait_rcu_gp during suspend path

From: Paul E. McKenney
Date: Thu Dec 18 2014 - 15:05:24 EST

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In reply to: Arun KS: "Re: [RCU] kernel hangs in wait_rcu_gp during suspend path"
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On Thu, Dec 18, 2014 at 09:52:28PM +0530, Arun KS wrote:
> Hi Paul,
>
> On Thu, Dec 18, 2014 at 12:54 AM, Paul E. McKenney
> <paulmck@xxxxxxxxxxxxxxxxxx> wrote:
> > On Tue, Dec 16, 2014 at 11:00:20PM +0530, Arun KS wrote:
> >> Hello,
> >>
> >> Adding some more info.
> >>
> >> Below is the rcu_data data structure corresponding to cpu4.
> >
> > This shows that RCU is idle. What was the state of the system at the
> > time you collected this data?
>
> System initiated a suspend sequence and currently at disable_nonboot_cpus().
> It has hotplugged 0, 1 and 2 successfully. And even successful in hot
> plugging cpu3.
> But while calling the CPU_POST_DEAD notifier for cpu3, another driver tried to
> unregister an atomic notifier. Which eventually calls syncronize_rcu()
> which hangs the suspend task.
>
> bt as follows,
> PID: 202 TASK: edcd2a00 CPU: 4 COMMAND: "kworker/u16:4"
> #0 [<c0a1f8c0>] (__schedule) from [<c0a1d054>]
> #1 [<c0a1d054>] (schedule_timeout) from [<c0a1f018>]
> #2 [<c0a1f018>] (wait_for_common) from [<c013c570>]
> #3 [<c013c570>] (wait_rcu_gp) from [<c014407c>]
> #4 [<c014407c>] (atomic_notifier_chain_unregister) from [<c06be62c>]
> #5 [<c06be62c>] (cpufreq_interactive_disable_sched_input) from [<c06bee1c>]
> #6 [<c06bee1c>] (cpufreq_governor_interactive) from [<c06b7724>]
> #7 [<c06b7724>] (__cpufreq_governor) from [<c06b9f74>]
> #8 [<c06b9f74>] (__cpufreq_remove_dev_finish) from [<c06ba3a4>]
> #9 [<c06ba3a4>] (cpufreq_cpu_callback) from [<c0a22674>]
> #10 [<c0a22674>] (notifier_call_chain) from [<c012284c>]
> #11 [<c012284c>] (__cpu_notify) from [<c01229dc>]
> #12 [<c01229dc>] (cpu_notify_nofail) from [<c0a0dd1c>]
> #13 [<c0a0dd1c>] (_cpu_down) from [<c0122b48>]
> #14 [<c0122b48>] (disable_nonboot_cpus) from [<c0168cd8>]
> #15 [<c0168cd8>] (suspend_devices_and_enter) from [<c0169018>]
> #16 [<c0169018>] (pm_suspend) from [<c01691e0>]
> #17 [<c01691e0>] (try_to_suspend) from [<c01396f0>]
> #18 [<c01396f0>] (process_one_work) from [<c0139db0>]
> #19 [<c0139db0>] (worker_thread) from [<c013efa4>]
> #20 [<c013efa4>] (kthread) from [<c01061f8>]
>
> But the other cores 4-7 are active. I can see them going to idle tasks
> coming out from idle because of interrupts, scheduling kworkers etc.
> So when I took the data, all the online cores(4-7) were in idle as
> shown below from runq data structures.
>
> ------start--------------
> crash> runq
> CPU 0 [OFFLINE]
>
> CPU 1 [OFFLINE]
>
> CPU 2 [OFFLINE]
>
> CPU 3 [OFFLINE]
>
> CPU 4 RUNQUEUE: c5439040
> CURRENT: PID: 0 TASK: f0c9d400 COMMAND: "swapper/4"
> RT PRIO_ARRAY: c5439130
> [no tasks queued]
> CFS RB_ROOT: c54390c0
> [no tasks queued]
>
> CPU 5 RUNQUEUE: c5447040
> CURRENT: PID: 0 TASK: f0c9aa00 COMMAND: "swapper/5"
> RT PRIO_ARRAY: c5447130
> [no tasks queued]
> CFS RB_ROOT: c54470c0
> [no tasks queued]
>
> CPU 6 RUNQUEUE: c5455040
> CURRENT: PID: 0 TASK: f0c9ce00 COMMAND: "swapper/6"
> RT PRIO_ARRAY: c5455130
> [no tasks queued]
> CFS RB_ROOT: c54550c0
> [no tasks queued]
>
> CPU 7 RUNQUEUE: c5463040
> CURRENT: PID: 0 TASK: f0c9b000 COMMAND: "swapper/7"
> RT PRIO_ARRAY: c5463130
> [no tasks queued]
> CFS RB_ROOT: c54630c0
> [no tasks queued]
> ------end--------------
>
> but one strange thing i can see is that rcu_read_lock_nesting for idle
> tasks running on cpu 5 and cpu 6 are set to 1.
>
> PID: 0 TASK: f0c9d400 CPU: 4 COMMAND: "swapper/4"
> rcu_read_lock_nesting = 0,
>
> PID: 0 TASK: f0c9aa00 CPU: 5 COMMAND: "swapper/5"
> rcu_read_lock_nesting = 1,
>
> PID: 0 TASK: f0c9ce00 CPU: 6 COMMAND: "swapper/6"
> rcu_read_lock_nesting = 1,
>
> PID: 0 TASK: f0c9b000 CPU: 7 COMMAND: "swapper/7"
> rcu_read_lock_nesting = 0,
>
> Does this means that the current grace period(suspend thread is
> waiting on) is getting extended infinitely?

Indeed it does, good catch! Looks like someone entered an RCU read-side
critical section, then forgot to exit it, which would prevent grace
periods from ever completing. CONFIG_PROVE_RCU=y might be
helpful in tracking this down.

> Also attaching the per_cpu rcu_data for online and offline cores.

But these still look like there is no grace period in progress.

Still, it would be good to try CONFIG_PROVE_RCU=y and see what it
shows you.

Also, I am not seeing similar complaints about 3.10, so it is quite
possible that a recent change in the ARM-specific idle-loop code is
doing this to you. It might be well worth looking through recent
changes in this area, particularly if some older version works well
for you.

Thanx, Paul

> Thanks,
> Arun
>
> >
> > Thanx, Paul
> >
> >> struct rcu_data {
> >> completed = 5877,
> >> gpnum = 5877,
> >> passed_quiesce = true,
> >> qs_pending = false,
> >> beenonline = true,
> >> preemptible = true,
> >> mynode = 0xc117f340 <rcu_preempt_state>,
> >> grpmask = 16,
> >> nxtlist = 0xedaaec00,
> >> nxttail = {0xc54366c4, 0xe84d350c, 0xe84d350c, 0xe84d350c},
> >> nxtcompleted = {4294967035, 5878, 5878, 5878},
> >> qlen_lazy = 105,
> >> qlen = 415,
> >> qlen_last_fqs_check = 0,
> >> n_cbs_invoked = 86323,
> >> n_nocbs_invoked = 0,
> >> n_cbs_orphaned = 0,
> >> n_cbs_adopted = 139,
> >> n_force_qs_snap = 0,
> >> blimit = 10,
> >> dynticks = 0xc5436758,
> >> dynticks_snap = 7582140,
> >> dynticks_fqs = 41,
> >> offline_fqs = 0,
> >> n_rcu_pending = 59404,
> >> n_rp_qs_pending = 5,
> >> n_rp_report_qs = 4633,
> >> n_rp_cb_ready = 32,
> >> n_rp_cpu_needs_gp = 41088,
> >> n_rp_gp_completed = 2844,
> >> n_rp_gp_started = 1150,
> >> n_rp_need_nothing = 9657,
> >> barrier_head = {
> >> next = 0x0,
> >> func = 0x0
> >> },
> >> oom_head = {
> >> next = 0x0,
> >> func = 0x0
> >> },
> >> cpu = 4,
> >> rsp = 0xc117f340 <rcu_preempt_state>
> >> }
> >>
> >>
> >>
> >> Also pasting complete rcu_preempt_state.
> >>
> >>
> >>
> >> rcu_preempt_state = $9 = {
> >> node = {{
> >> lock = {
> >> raw_lock = {
> >> {
> >> slock = 3129850509,
> >> tickets = {
> >> owner = 47757,
> >> next = 47757
> >> }
> >> }
> >> },
> >> magic = 3735899821,
> >> owner_cpu = 4294967295,
> >> owner = 0xffffffff
> >> },
> >> gpnum = 5877,
> >> completed = 5877,
> >> qsmask = 0,
> >> expmask = 0,
> >> qsmaskinit = 240,
> >> grpmask = 0,
> >> grplo = 0,
> >> grphi = 7,
> >> grpnum = 0 '\000',
> >> level = 0 '\000',
> >> parent = 0x0,
> >> blkd_tasks = {
> >> next = 0xc117f378 <rcu_preempt_state+56>,
> >> prev = 0xc117f378 <rcu_preempt_state+56>
> >> },
> >> gp_tasks = 0x0,
> >> exp_tasks = 0x0,
> >> need_future_gp = {1, 0},
> >> fqslock = {
> >> raw_lock = {
> >> {
> >> slock = 0,
> >> tickets = {
> >> owner = 0,
> >> next = 0
> >> }
> >> }
> >> },
> >> magic = 3735899821,
> >> owner_cpu = 4294967295,
> >> owner = 0xffffffff
> >> }
> >> }},
> >> level = {0xc117f340 <rcu_preempt_state>},
> >> levelcnt = {1, 0, 0, 0, 0},
> >> levelspread = "\b",
> >> rda = 0xc115e6b0 <rcu_preempt_data>,
> >> call = 0xc01975ac <call_rcu>,
> >> fqs_state = 0 '\000',
> >> boost = 0 '\000',
> >> gpnum = 5877,
> >> completed = 5877,
> >> gp_kthread = 0xf0c9e600,
> >> gp_wq = {
> >> lock = {
> >> {
> >> rlock = {
> >> raw_lock = {
> >> {
> >> slock = 2160230594,
> >> tickets = {
> >> owner = 32962,
> >> next = 32962
> >> }
> >> }
> >> },
> >> magic = 3735899821,
> >> owner_cpu = 4294967295,
> >> owner = 0xffffffff
> >> }
> >> }
> >> },
> >> task_list = {
> >> next = 0xf0cd1f20,
> >> prev = 0xf0cd1f20
> >> }
> >> },
> >> gp_flags = 1,
> >> orphan_lock = {
> >> raw_lock = {
> >> {
> >> slock = 327685,
> >> tickets = {
> >> owner = 5,
> >> next = 5
> >> }
> >> }
> >> },
> >> magic = 3735899821,
> >> owner_cpu = 4294967295,
> >> owner = 0xffffffff
> >> },
> >> orphan_nxtlist = 0x0,
> >> orphan_nxttail = 0xc117f490 <rcu_preempt_state+336>,
> >> orphan_donelist = 0x0,
> >> orphan_donetail = 0xc117f498 <rcu_preempt_state+344>,
> >> qlen_lazy = 0,
> >> qlen = 0,
> >> onoff_mutex = {
> >> count = {
> >> counter = 1
> >> },
> >> wait_lock = {
> >> {
> >> rlock = {
> >> raw_lock = {
> >> {
> >> slock = 811479134,
> >> tickets = {
> >> owner = 12382,
> >> next = 12382
> >> }
> >> }
> >> },
> >> magic = 3735899821,
> >> owner_cpu = 4294967295,
> >> owner = 0xffffffff
> >> }
> >> }
> >> },
> >> wait_list = {
> >> next = 0xc117f4bc <rcu_preempt_state+380>,
> >> prev = 0xc117f4bc <rcu_preempt_state+380>
> >> },
> >> owner = 0x0,
> >> name = 0x0,
> >> magic = 0xc117f4a8 <rcu_preempt_state+360>
> >> },
> >> barrier_mutex = {
> >> count = {
> >> counter = 1
> >> },
> >> wait_lock = {
> >> {
> >> rlock = {
> >> raw_lock = {
> >> {
> >> slock = 0,
> >> tickets = {
> >> owner = 0,
> >> next = 0
> >> }
> >> }
> >> },
> >> magic = 3735899821,
> >> owner_cpu = 4294967295,
> >> owner = 0xffffffff
> >> }
> >> }
> >> },
> >> wait_list = {
> >> next = 0xc117f4e4 <rcu_preempt_state+420>,
> >> prev = 0xc117f4e4 <rcu_preempt_state+420>
> >> },
> >> owner = 0x0,
> >> name = 0x0,
> >> magic = 0xc117f4d0 <rcu_preempt_state+400>
> >> },
> >> barrier_cpu_count = {
> >> counter = 0
> >> },
> >> barrier_completion = {
> >> done = 0,
> >> wait = {
> >> lock = {
> >> {
> >> rlock = {
> >> raw_lock = {
> >> {
> >> slock = 0,
> >> tickets = {
> >> owner = 0,
> >> next = 0
> >> }
> >> }
> >> },
> >> magic = 0,
> >> owner_cpu = 0,
> >> owner = 0x0
> >> }
> >> }
> >> },
> >> task_list = {
> >> next = 0x0,
> >> prev = 0x0
> >> }
> >> }
> >> },
> >> n_barrier_done = 0,
> >> expedited_start = {
> >> counter = 0
> >> },
> >> expedited_done = {
> >> counter = 0
> >> },
> >> expedited_wrap = {
> >> counter = 0
> >> },
> >> expedited_tryfail = {
> >> counter = 0
> >> },
> >> expedited_workdone1 = {
> >> counter = 0
> >> },
> >> expedited_workdone2 = {
> >> counter = 0
> >> },
> >> expedited_normal = {
> >> counter = 0
> >> },
> >> expedited_stoppedcpus = {
> >> counter = 0
> >> },
> >> expedited_done_tries = {
> >> counter = 0
> >> },
> >> expedited_done_lost = {
> >> counter = 0
> >> },
> >> expedited_done_exit = {
> >> counter = 0
> >> },
> >> jiffies_force_qs = 4294963917,
> >> n_force_qs = 4028,
> >> n_force_qs_lh = 0,
> >> n_force_qs_ngp = 0,
> >> gp_start = 4294963911,
> >> jiffies_stall = 4294966011,
> >> gp_max = 17,
> >> name = 0xc0d833ab "rcu_preempt",
> >> abbr = 112 'p',
> >> flavors = {
> >> next = 0xc117f2ec <rcu_bh_state+556>,
> >> prev = 0xc117f300 <rcu_struct_flavors>
> >> },
> >> wakeup_work = {
> >> flags = 3,
> >> llnode = {
> >> next = 0x0
> >> },
> >> func = 0xc0195aa8 <rsp_wakeup>
> >> }
> >> }
> >>
> >> Hope this helps.
> >>
> >> Thanks,
> >> Arun
> >>
> >>
> >> On Tue, Dec 16, 2014 at 11:59 AM, Arun KS <arunks.linux@xxxxxxxxx> wrote:
> >> > Hello,
> >> >
> >> > I dig little deeper to understand the situation.
> >> > All other cpus are in idle thread already.
> >> > As per my understanding, for the grace period to end, at-least one of
> >> > the following should happen on all online cpus,
> >> >
> >> > 1. a context switch.
> >> > 2. user space switch.
> >> > 3. switch to idle thread.
> >> >
> >> > In this situation, since all the other cores are already in idle, non
> >> > of the above are meet on all online cores.
> >> > So grace period is getting extended and never finishes. Below is the
> >> > state of runqueue when the hang happens.
> >> > --------------start------------------------------------
> >> > crash> runq
> >> > CPU 0 [OFFLINE]
> >> >
> >> > CPU 1 [OFFLINE]
> >> >
> >> > CPU 2 [OFFLINE]
> >> >
> >> > CPU 3 [OFFLINE]
> >> >
> >> > CPU 4 RUNQUEUE: c3192e40
> >> > CURRENT: PID: 0 TASK: f0874440 COMMAND: "swapper/4"
> >> > RT PRIO_ARRAY: c3192f20
> >> > [no tasks queued]
> >> > CFS RB_ROOT: c3192eb0
> >> > [no tasks queued]
> >> >
> >> > CPU 5 RUNQUEUE: c31a0e40
> >> > CURRENT: PID: 0 TASK: f0874980 COMMAND: "swapper/5"
> >> > RT PRIO_ARRAY: c31a0f20
> >> > [no tasks queued]
> >> > CFS RB_ROOT: c31a0eb0
> >> > [no tasks queued]
> >> >
> >> > CPU 6 RUNQUEUE: c31aee40
> >> > CURRENT: PID: 0 TASK: f0874ec0 COMMAND: "swapper/6"
> >> > RT PRIO_ARRAY: c31aef20
> >> > [no tasks queued]
> >> > CFS RB_ROOT: c31aeeb0
> >> > [no tasks queued]
> >> >
> >> > CPU 7 RUNQUEUE: c31bce40
> >> > CURRENT: PID: 0 TASK: f0875400 COMMAND: "swapper/7"
> >> > RT PRIO_ARRAY: c31bcf20
> >> > [no tasks queued]
> >> > CFS RB_ROOT: c31bceb0
> >> > [no tasks queued]
> >> > --------------end------------------------------------
> >> >
> >> > If my understanding is correct the below patch should help, because it
> >> > will expedite grace periods during suspend,
> >> > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=d1d74d14e98a6be740a6f12456c7d9ad47be9c9c
> >> >
> >> > But I wonder why it was not taken to stable trees. Can we take it?
> >> > Appreciate your help.
> >> >
> >> > Thanks,
> >> > Arun
> >> >
> >> > On Mon, Dec 15, 2014 at 10:34 PM, Arun KS <arunks.linux@xxxxxxxxx> wrote:
> >> >> Hi,
> >> >>
> >> >> Here is the backtrace of the process hanging in wait_rcu_gp,
> >> >>
> >> >> PID: 247 TASK: e16e7380 CPU: 4 COMMAND: "kworker/u16:5"
> >> >> #0 [<c09fead0>] (__schedule) from [<c09fcab0>]
> >> >> #1 [<c09fcab0>] (schedule_timeout) from [<c09fe050>]
> >> >> #2 [<c09fe050>] (wait_for_common) from [<c013b2b4>]
> >> >> #3 [<c013b2b4>] (wait_rcu_gp) from [<c0142f50>]
> >> >> #4 [<c0142f50>] (atomic_notifier_chain_unregister) from [<c06b2ab8>]
> >> >> #5 [<c06b2ab8>] (cpufreq_interactive_disable_sched_input) from [<c06b32a8>]
> >> >> #6 [<c06b32a8>] (cpufreq_governor_interactive) from [<c06abbf8>]
> >> >> #7 [<c06abbf8>] (__cpufreq_governor) from [<c06ae474>]
> >> >> #8 [<c06ae474>] (__cpufreq_remove_dev_finish) from [<c06ae8c0>]
> >> >> #9 [<c06ae8c0>] (cpufreq_cpu_callback) from [<c0a0185c>]
> >> >> #10 [<c0a0185c>] (notifier_call_chain) from [<c0121888>]
> >> >> #11 [<c0121888>] (__cpu_notify) from [<c0121a04>]
> >> >> #12 [<c0121a04>] (cpu_notify_nofail) from [<c09ee7f0>]
> >> >> #13 [<c09ee7f0>] (_cpu_down) from [<c0121b70>]
> >> >> #14 [<c0121b70>] (disable_nonboot_cpus) from [<c016788c>]
> >> >> #15 [<c016788c>] (suspend_devices_and_enter) from [<c0167bcc>]
> >> >> #16 [<c0167bcc>] (pm_suspend) from [<c0167d94>]
> >> >> #17 [<c0167d94>] (try_to_suspend) from [<c0138460>]
> >> >> #18 [<c0138460>] (process_one_work) from [<c0138b18>]
> >> >> #19 [<c0138b18>] (worker_thread) from [<c013dc58>]
> >> >> #20 [<c013dc58>] (kthread) from [<c01061b8>]
> >> >>
> >> >> Will this patch helps here,
> >> >> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=d1d74d14e98a6be740a6f12456c7d9ad47be9c9c
> >> >>
> >> >> I couldn't really understand why it got struck in synchronize_rcu().
> >> >> Please give some pointers to debug this further.
> >> >>
> >> >> Below are the configs enable related to RCU.
> >> >>
> >> >> CONFIG_TREE_PREEMPT_RCU=y
> >> >> CONFIG_PREEMPT_RCU=y
> >> >> CONFIG_RCU_STALL_COMMON=y
> >> >> CONFIG_RCU_FANOUT=32
> >> >> CONFIG_RCU_FANOUT_LEAF=16
> >> >> CONFIG_RCU_FAST_NO_HZ=y
> >> >> CONFIG_RCU_CPU_STALL_TIMEOUT=21
> >> >> CONFIG_RCU_CPU_STALL_VERBOSE=y
> >> >>
> >> >> Kernel version is 3.10.28
> >> >> Architecture is ARM
> >> >>
> >> >> Thanks,
> >> >> Arun
> >>
> >

> crash> struct rcu_data C54286B0
> struct rcu_data {
> completed = 2833,
> gpnum = 2833,
> passed_quiesce = false,
> qs_pending = false,
> beenonline = true,
> preemptible = true,
> mynode = 0xc117f340 <rcu_preempt_state>,
> grpmask = 8,
> nxtlist = 0x0,
> nxttail = {0xc54286c4, 0xc54286c4, 0xc54286c4, 0x0},
> nxtcompleted = {0, 4294967136, 4294967137, 4294967137},
> qlen_lazy = 0,
> qlen = 0,
> qlen_last_fqs_check = 0,
> n_cbs_invoked = 609,
> n_nocbs_invoked = 0,
> n_cbs_orphaned = 13,
> n_cbs_adopted = 0,
> n_force_qs_snap = 1428,
> blimit = 10,
> dynticks = 0xc5428758,
> dynticks_snap = 13206053,
> dynticks_fqs = 16,
> offline_fqs = 0,
> n_rcu_pending = 181,
> n_rp_qs_pending = 1,
> n_rp_report_qs = 21,
> n_rp_cb_ready = 0,
> n_rp_cpu_needs_gp = 0,
> n_rp_gp_completed = 22,
> n_rp_gp_started = 8,
> n_rp_need_nothing = 130,
> barrier_head = {
> next = 0x0,
> func = 0x0
> },
> oom_head = {
> next = 0x0,
> func = 0x0
> },
> cpu = 3,
> rsp = 0xc117f340 <rcu_preempt_state>
> }
>
> crash> struct rcu_data C541A6B0
> struct rcu_data {
> completed = 5877,
> gpnum = 5877,
> passed_quiesce = true,
> qs_pending = false,
> beenonline = true,
> preemptible = true,
> mynode = 0xc117f340 <rcu_preempt_state>,
> grpmask = 4,
> nxtlist = 0x0,
> nxttail = {0xc541a6c4, 0xc541a6c4, 0xc541a6c4, 0x0},
> nxtcompleted = {0, 5877, 5878, 5878},
> qlen_lazy = 0,
> qlen = 0,
> qlen_last_fqs_check = 0,
> n_cbs_invoked = 61565,
> n_nocbs_invoked = 0,
> n_cbs_orphaned = 139,
> n_cbs_adopted = 100,
> n_force_qs_snap = 0,
> blimit = 10,
> dynticks = 0xc541a758,
> dynticks_snap = 13901017,
> dynticks_fqs = 75,
> offline_fqs = 0,
> n_rcu_pending = 16546,
> n_rp_qs_pending = 3,
> n_rp_report_qs = 4539,
> n_rp_cb_ready = 69,
> n_rp_cpu_needs_gp = 782,
> n_rp_gp_completed = 4196,
> n_rp_gp_started = 1739,
> n_rp_need_nothing = 5221,
> barrier_head = {
> next = 0x0,
> func = 0x0
> },
> oom_head = {
> next = 0x0,
> func = 0x0
> },
> cpu = 2,
> rsp = 0xc117f340 <rcu_preempt_state>
> }
>
> crash> struct rcu_data C540C6B0
> struct rcu_data {
> completed = 5877,
> gpnum = 5877,
> passed_quiesce = true,
> qs_pending = false,
> beenonline = true,
> preemptible = true,
> mynode = 0xc117f340 <rcu_preempt_state>,
> grpmask = 2,
> nxtlist = 0x0,
> nxttail = {0xc540c6c4, 0xc540c6c4, 0xc540c6c4, 0x0},
> nxtcompleted = {4294967030, 5878, 5878, 5878},
> qlen_lazy = 0,
> qlen = 0,
> qlen_last_fqs_check = 0,
> n_cbs_invoked = 74292,
> n_nocbs_invoked = 0,
> n_cbs_orphaned = 100,
> n_cbs_adopted = 65,
> n_force_qs_snap = 0,
> blimit = 10,
> dynticks = 0xc540c758,
> dynticks_snap = 10753433,
> dynticks_fqs = 69,
> offline_fqs = 0,
> n_rcu_pending = 18350,
> n_rp_qs_pending = 6,
> n_rp_report_qs = 5009,
> n_rp_cb_ready = 50,
> n_rp_cpu_needs_gp = 915,
> n_rp_gp_completed = 4423,
> n_rp_gp_started = 1826,
> n_rp_need_nothing = 6127,
> barrier_head = {
> next = 0x0,
> func = 0x0
> },
> oom_head = {
> next = 0x0,
> func = 0x0
> },
> cpu = 1,
> rsp = 0xc117f340 <rcu_preempt_state>
> }
> crash> struct rcu_data C53FE6B0
> struct rcu_data {
> completed = 5877,
> gpnum = 5877,
> passed_quiesce = true,
> qs_pending = false,
> beenonline = true,
> preemptible = true,
> mynode = 0xc117f340 <rcu_preempt_state>,
> grpmask = 1,
> nxtlist = 0x0,
> nxttail = {0xc53fe6c4, 0xc53fe6c4, 0xc53fe6c4, 0x0},
> nxtcompleted = {4294966997, 5875, 5876, 5876},
> qlen_lazy = 0,
> qlen = 0,
> qlen_last_fqs_check = 0,
> n_cbs_invoked = 123175,
> n_nocbs_invoked = 0,
> n_cbs_orphaned = 52,
> n_cbs_adopted = 0,
> n_force_qs_snap = 0,
> blimit = 10,
> dynticks = 0xc53fe758,
> dynticks_snap = 6330446,
> dynticks_fqs = 46,
> offline_fqs = 0,
> n_rcu_pending = 22529,
> n_rp_qs_pending = 3,
> n_rp_report_qs = 5290,
> n_rp_cb_ready = 279,
> n_rp_cpu_needs_gp = 740,
> n_rp_gp_completed = 2707,
> n_rp_gp_started = 1208,
> n_rp_need_nothing = 12305,
> barrier_head = {
> next = 0x0,
> func = 0x0
> },
> oom_head = {
> next = 0x0,
> func = 0x0
> },
> cpu = 0,
> rsp = 0xc117f340 <rcu_preempt_state>
> }
>

> crash> struct rcu_data c54366b0
> struct rcu_data {
> completed = 5877,
> gpnum = 5877,
> passed_quiesce = true,
> qs_pending = false,
> beenonline = true,
> preemptible = true,
> mynode = 0xc117f340 <rcu_preempt_state>,
> grpmask = 16,
> nxtlist = 0xedaaec00,
> nxttail = {0xc54366c4, 0xe84d350c, 0xe84d350c, 0xe84d350c},
> nxtcompleted = {4294967035, 5878, 5878, 5878},
> qlen_lazy = 105,
> qlen = 415,
> qlen_last_fqs_check = 0,
> n_cbs_invoked = 86323,
> n_nocbs_invoked = 0,
> n_cbs_orphaned = 0,
> n_cbs_adopted = 139,
> n_force_qs_snap = 0,
> blimit = 10,
> dynticks = 0xc5436758,
> dynticks_snap = 7582140,
> dynticks_fqs = 41,
> offline_fqs = 0,
> n_rcu_pending = 59404,
> n_rp_qs_pending = 5,
> n_rp_report_qs = 4633,
> n_rp_cb_ready = 32,
> n_rp_cpu_needs_gp = 41088,
> n_rp_gp_completed = 2844,
> n_rp_gp_started = 1150,
> n_rp_need_nothing = 9657,
> barrier_head = {
> next = 0x0,
> func = 0x0
> },
> oom_head = {
> next = 0x0,
> func = 0x0
> },
> cpu = 4,
> rsp = 0xc117f340 <rcu_preempt_state>
> }
>
> crash> struct rcu_data c54446b0
> struct rcu_data {
> completed = 5877,
> gpnum = 5877,
> passed_quiesce = true,
> qs_pending = false,
> beenonline = true,
> preemptible = true,
> mynode = 0xc117f340 <rcu_preempt_state>,
> grpmask = 32,
> nxtlist = 0xcf9e856c,
> nxttail = {0xc54446c4, 0xcfb3050c, 0xcfb3050c, 0xcfb3050c},
> nxtcompleted = {0, 5878, 5878, 5878},
> qlen_lazy = 0,
> qlen = 117,
> qlen_last_fqs_check = 0,
> n_cbs_invoked = 36951,
> n_nocbs_invoked = 0,
> n_cbs_orphaned = 0,
> n_cbs_adopted = 0,
> n_force_qs_snap = 1428,
> blimit = 10,
> dynticks = 0xc5444758,
> dynticks_snap = 86034,
> dynticks_fqs = 46,
> offline_fqs = 0,
> n_rcu_pending = 49104,
> n_rp_qs_pending = 3,
> n_rp_report_qs = 2360,
> n_rp_cb_ready = 18,
> n_rp_cpu_needs_gp = 40106,
> n_rp_gp_completed = 1334,
> n_rp_gp_started = 791,
> n_rp_need_nothing = 4495,
> barrier_head = {
> next = 0x0,
> func = 0x0
> },
> oom_head = {
> next = 0x0,
> func = 0x0
> },
> cpu = 5,
> rsp = 0xc117f340 <rcu_preempt_state>
> }
>
> crash> struct rcu_data c54526b0
> struct rcu_data {
> completed = 5877,
> gpnum = 5877,
> passed_quiesce = true,
> qs_pending = false,
> beenonline = true,
> preemptible = true,
> mynode = 0xc117f340 <rcu_preempt_state>,
> grpmask = 64,
> nxtlist = 0xe613d200,
> nxttail = {0xc54526c4, 0xe6fc9d0c, 0xe6fc9d0c, 0xe6fc9d0c},
> nxtcompleted = {0, 5878, 5878, 5878},
> qlen_lazy = 2,
> qlen = 35,
> qlen_last_fqs_check = 0,
> n_cbs_invoked = 34459,
> n_nocbs_invoked = 0,
> n_cbs_orphaned = 0,
> n_cbs_adopted = 0,
> n_force_qs_snap = 1428,
> blimit = 10,
> dynticks = 0xc5452758,
> dynticks_snap = 116840,
> dynticks_fqs = 47,
> offline_fqs = 0,
> n_rcu_pending = 48486,
> n_rp_qs_pending = 3,
> n_rp_report_qs = 2223,
> n_rp_cb_ready = 24,
> n_rp_cpu_needs_gp = 40101,
> n_rp_gp_completed = 1226,
> n_rp_gp_started = 789,
> n_rp_need_nothing = 4123,
> barrier_head = {
> next = 0x0,
> func = 0x0
> },
> oom_head = {
> next = 0x0,
> func = 0x0
> },
> cpu = 6,
> rsp = 0xc117f340 <rcu_preempt_state>
> }
>
> crash> struct rcu_data c54606b0
> struct rcu_data {
> completed = 5877,
> gpnum = 5877,
> passed_quiesce = true,
> qs_pending = false,
> beenonline = true,
> preemptible = true,
> mynode = 0xc117f340 <rcu_preempt_state>,
> grpmask = 128,
> nxtlist = 0xdec32a6c,
> nxttail = {0xc54606c4, 0xe6fcf10c, 0xe6fcf10c, 0xe6fcf10c},
> nxtcompleted = {0, 5878, 5878, 5878},
> qlen_lazy = 1,
> qlen = 30,
> qlen_last_fqs_check = 0,
> n_cbs_invoked = 31998,
> n_nocbs_invoked = 0,
> n_cbs_orphaned = 0,
> n_cbs_adopted = 0,
> n_force_qs_snap = 1428,
> blimit = 10,
> dynticks = 0xc5460758,
> dynticks_snap = 57846,
> dynticks_fqs = 54,
> offline_fqs = 0,
> n_rcu_pending = 47502,
> n_rp_qs_pending = 2,
> n_rp_report_qs = 2142,
> n_rp_cb_ready = 37,
> n_rp_cpu_needs_gp = 40049,
> n_rp_gp_completed = 1223,
> n_rp_gp_started = 661,
> n_rp_need_nothing = 3390,
> barrier_head = {
> next = 0x0,
> func = 0x0
> },
> oom_head = {
> next = 0x0,
> func = 0x0
> },
> cpu = 7,
> rsp = 0xc117f340 <rcu_preempt_state>
> }

>
> rcu_preempt_state = $9 = {
> node = {{
> lock = {
> raw_lock = {
> {
> slock = 3129850509,
> tickets = {
> owner = 47757,
> next = 47757
> }
> }
> },
> magic = 3735899821,
> owner_cpu = 4294967295,
> owner = 0xffffffff
> },
> gpnum = 5877,
> completed = 5877,
> qsmask = 0,
> expmask = 0,
> qsmaskinit = 240,
> grpmask = 0,
> grplo = 0,
> grphi = 7,
> grpnum = 0 '\000',
> level = 0 '\000',
> parent = 0x0,
> blkd_tasks = {
> next = 0xc117f378 <rcu_preempt_state+56>,
> prev = 0xc117f378 <rcu_preempt_state+56>
> },
> gp_tasks = 0x0,
> exp_tasks = 0x0,
> need_future_gp = {1, 0},
> fqslock = {
> raw_lock = {
> {
> slock = 0,
> tickets = {
> owner = 0,
> next = 0
> }
> }
> },
> magic = 3735899821,
> owner_cpu = 4294967295,
> owner = 0xffffffff
> }
> }},
> level = {0xc117f340 <rcu_preempt_state>},
> levelcnt = {1, 0, 0, 0, 0},
> levelspread = "\b",
> rda = 0xc115e6b0 <rcu_preempt_data>,
> call = 0xc01975ac <call_rcu>,
> fqs_state = 0 '\000',
> boost = 0 '\000',
> gpnum = 5877,
> completed = 5877,
> gp_kthread = 0xf0c9e600,
> gp_wq = {
> lock = {
> {
> rlock = {
> raw_lock = {
> {
> slock = 2160230594,
> tickets = {
> owner = 32962,
> next = 32962
> }
> }
> },
> magic = 3735899821,
> owner_cpu = 4294967295,
> owner = 0xffffffff
> }
> }
> },
> task_list = {
> next = 0xf0cd1f20,
> prev = 0xf0cd1f20
> }
> },
> gp_flags = 1,
> orphan_lock = {
> raw_lock = {
> {
> slock = 327685,
> tickets = {
> owner = 5,
> next = 5
> }
> }
> },
> magic = 3735899821,
> owner_cpu = 4294967295,
> owner = 0xffffffff
> },
> orphan_nxtlist = 0x0,
> orphan_nxttail = 0xc117f490 <rcu_preempt_state+336>,
> orphan_donelist = 0x0,
> orphan_donetail = 0xc117f498 <rcu_preempt_state+344>,
> qlen_lazy = 0,
> qlen = 0,
> onoff_mutex = {
> count = {
> counter = 1
> },
> wait_lock = {
> {
> rlock = {
> raw_lock = {
> {
> slock = 811479134,
> tickets = {
> owner = 12382,
> next = 12382
> }
> }
> },
> magic = 3735899821,
> owner_cpu = 4294967295,
> owner = 0xffffffff
> }
> }
> },
> wait_list = {
> next = 0xc117f4bc <rcu_preempt_state+380>,
> prev = 0xc117f4bc <rcu_preempt_state+380>
> },
> owner = 0x0,
> name = 0x0,
> magic = 0xc117f4a8 <rcu_preempt_state+360>
> },
> barrier_mutex = {
> count = {
> counter = 1
> },
> wait_lock = {
> {
> rlock = {
> raw_lock = {
> {
> slock = 0,
> tickets = {
> owner = 0,
> next = 0
> }
> }
> },
> magic = 3735899821,
> owner_cpu = 4294967295,
> owner = 0xffffffff
> }
> }
> },
> wait_list = {
> next = 0xc117f4e4 <rcu_preempt_state+420>,
> prev = 0xc117f4e4 <rcu_preempt_state+420>
> },
> owner = 0x0,
> name = 0x0,
> magic = 0xc117f4d0 <rcu_preempt_state+400>
> },
> barrier_cpu_count = {
> counter = 0
> },
> barrier_completion = {
> done = 0,
> wait = {
> lock = {
> {
> rlock = {
> raw_lock = {
> {
> slock = 0,
> tickets = {
> owner = 0,
> next = 0
> }
> }
> },
> magic = 0,
> owner_cpu = 0,
> owner = 0x0
> }
> }
> },
> task_list = {
> next = 0x0,
> prev = 0x0
> }
> }
> },
> n_barrier_done = 0,
> expedited_start = {
> counter = 0
> },
> expedited_done = {
> counter = 0
> },
> expedited_wrap = {
> counter = 0
> },
> expedited_tryfail = {
> counter = 0
> },
> expedited_workdone1 = {
> counter = 0
> },
> expedited_workdone2 = {
> counter = 0
> },
> expedited_normal = {
> counter = 0
> },
> expedited_stoppedcpus = {
> counter = 0
> },
> expedited_done_tries = {
> counter = 0
> },
> expedited_done_lost = {
> counter = 0
> },
> expedited_done_exit = {
> counter = 0
> },
> jiffies_force_qs = 4294963917,
> n_force_qs = 4028,
> n_force_qs_lh = 0,
> n_force_qs_ngp = 0,
> gp_start = 4294963911,
> jiffies_stall = 4294966011,
> gp_max = 17,
> name = 0xc0d833ab "rcu_preempt",
> abbr = 112 'p',
> flavors = {
> next = 0xc117f2ec <rcu_bh_state+556>,
> prev = 0xc117f300 <rcu_struct_flavors>
> },
> wakeup_work = {
> flags = 3,
> llnode = {
> next = 0x0
> },
> func = 0xc0195aa8 <rsp_wakeup>
> }
>
>

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