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Message-ID: <CAKZGPAND7TPZKbTqG-zL_Vx=E_k3kio=onwppTJqVcVSmjOR6w@mail.gmail.com>
Date: Tue, 16 Dec 2014 23:00:20 +0530
From: Arun KS <arunks.linux@...il.com>
To: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc: Paul McKenney <paulmck@...ux.vnet.ibm.com>, josh@...htriplett.org,
rostedt@...dmis.org,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
laijs@...fujitsu.com
Subject: Re: [RCU] kernel hangs in wait_rcu_gp during suspend path
Hello,
Adding some more info.
Below is the rcu_data data structure corresponding to cpu4.
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@...il.com> 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@...il.com> 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
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