Re: BUG: rcu_sched detected stalls on CPUs

[Paul E. McKenney]

On Tue, May 09, 2017 at 10:53:25AM +0300, mitko@xxxxxxxxxx wrote:
> On 2017-05-08 16:24, Paul E. McKenney wrote:
> >On Mon, May 08, 2017 at 09:43:15AM +0300, mitko@xxxxxxxxxx wrote:
> >>On 2017-01-20 17:19, Steven Rostedt wrote:
> >>>On Fri, 20 Jan 2017 10:43:50 +0200
> >>>mitko@xxxxxxxxxx wrote:
> >>>
> >>>>[1.] One line summary of the problem:
> >>>>
> >>>>rcu_sched detected stalls on CPUs and few minutes server not respond.
> >>>
> >>>Is this reproducible? Or was this a one time ordeal?
> >>>
> >>>>
> >>>>[2.] Full description of the problem/report:
> >>>>
> >>>>Load of my server (postgres database) isnt big less then 0.50 and when
> >>>>error occured rcu_sched detected stalls on CPUs
> >>>>server freeze and nothing is work for 3-5 minute.
> >>>>No network, no video signal, no keyboard, no mouse. Nothing is worked.
> >>>>After these few minutes everything continue normal.
> >>>>This usual is happend once per day. When I check in google find a lots
> >>>>of ppl complain of this error, but no solution.
> >>>>Do any one know can help me to resolve it ? I spoke with few
> >>>>friends and
> >>>>they trying to convince me the problem is in CPU.
> >>>>I did not believe after a 3 years working CPU suddenly stop working
> >>>>correctly, but I might be wrong.
> >>>>
> >>>>[3.] Keywords (i.e., modules, networking, kernel):
> >>>>
> >>>>kernel
> >>>>
> >>>>[4.] Kernel information
> >>>>[4.1.] Kernel version (from /proc/version):
> >>>>
> >>>>Linux version 4.4.38 (root@hive64) (gcc version 5.4.0 (GCC) ) #2
> >>>>SMP Sun
> >>>>Dec 11 16:11:02 CST 2016
> >>>>
> >>>
> >>>Have you tried a newer version of the kernel?
> >>>
> >>>-- Steve
> >>
> >>
> >>Hello,
> >>yesterday I change to new kernel: 4.9.26 and still no effect.
> >>
> >>I trying to figure out what I need to buy because I read on google a
> >>lots of posts about that problem,
> >>some ppl suggest is BIOS firmware bug, some ppl tell that when they
> >>swap CPU problem is resolved.
> >>May be problem was started when I first time boot 4.x kernel and
> >>there have cpu microcode updates.
> >>Im 3.x kernels this feature was not in kernel, but I don't know,
> >>only guess.
> >>
> >>Can some one point me clearly: You need to change this one and
> >>problem will be solved ?
> >
> >Looking back at your earlier email, I see the following:
> >
> >[Wed Jan  4 10:19:12 2017] rcu_sched kthread starved for 60004
> >jiffies! g61967937 c61967936 f0x0 s3 ->state=0x1
> >
> >That indicates that the task "rcu_sched" isn't being allowed to run.
> >The "->state=0x1" indicates that this task is currently asleep and the
> >"s3" indicates that it is looking to start a grace period, but has not
> >progressed through this task.  My guess is that your system get very
> >busy, and that rcu_sched's normal scheduling priority is not sufficient
> >for it to be allowed to run.
> >
> >I therefore suggest that you try raising the rcu_sched task's priority.
> >
> >You can find this task like this:
> >
> >	ps -ef | grep rcu_sched
> >
> >On my laptop, I get this:
> >
> >	$ ps -ef | grep rcu_sched
> >	root         7     2  0 Apr11 ?        00:19:19 [rcu_sched]
> >	paulmck  18307 22926  0 06:11 pts/35   00:00:00 grep --color=auto
> >rcu_sche
> >
> >You can use the chrt command to set the priority.  For example,
> >given that
> >on my laptop, rcu_sched is PID 7:
> >
> >	sudo chrt -f -p 1 7
> >
> >You can double-check as follows:
> >
> >	$ chrt -p 7
> >	pid 7's current scheduling policy: SCHED_FIFO
> >	pid 7's current scheduling priority: 1
> >
> >Does that help?
> >
> >							Thanx, Paul
> >
> 
> 
> Hi,
> interesting ... I change priority as you suggest and will keep you
> in touch
> if the problem happens again because I cant reproduce it. Replay on
> your next email, I don't have any
> virtual servers / guest os on the server. It's server with only one
> process - redis server
> and in this time when error it's happened actually one of other
> servers start loading data
> into redis sever. Data is small 3-4 mil. keys every key contain
> around 150 symbols.
> I have that problem on two servers, next server is database server
> with postgresql
> and that problem happened more often, usual once per day or for few
> days.
> I never play before with changing priority of processes. When I check
> iLO log I saw logged error: power lost but server does not lost the
> power actually,
> it's just stop respond for 2-3 minutes and then continue normal
> operation with
> uptime more then 100 days.

Does redis keep any useful log?  If so, it would be worth looking into
what it thought that it was doing.

							Thanx, Paul

> Thanks for your suggestion.
> Regards,
> Mitko
> 
> 
> 
> 
> >>[239940.067938] clocksource: timekeeping watchdog on CPU26: Marking
> >>clocksource 'tsc' as unstable because the skew is too large:
> >>[239940.067943] clocksource:                       'hpet' wd_now:
> >>ecb521ce wd_last: ca45912d mask: ffffffff
> >>[239940.067946] clocksource:                       'tsc' cs_now:
> >>2d12df5f88d08 cs_last: 29fffbe2d36d6 mask: ffffffffffffffff
> >>[239940.068357] clocksource: Switched to clocksource hpet
> >>[240000.066457] INFO: rcu_sched detected stalls on CPUs/tasks:
> >>[240000.066488]         2-...: (38 GPs behind) idle=f1a/0/0
> >>softirq=2417028/2417028 fqs=0
> >>[240000.066491]         3-...: (27 GPs behind) idle=0bc/0/0
> >>softirq=3076046/3076047 fqs=0
> >>[240000.066494]         4-...: (1006 GPs behind) idle=308/0/0
> >>softirq=1474922/1474922 fqs=0
> >>[240000.066497]         5-...: (8034 GPs behind) idle=7b4/0/0
> >>softirq=69165/69166 fqs=0
> >>[240000.066499]         6-...: (1665 GPs behind) idle=716/0/0
> >>softirq=16465/16465 fqs=0
> >>[240000.066502]         7-...: (8034 GPs behind) idle=bd0/0/0
> >>softirq=15923/15924 fqs=0
> >>[240000.066505]         8-...: (1665 GPs behind) idle=a62/0/0
> >>softirq=93861/93861 fqs=0
> >>[240000.066507]         9-...: (1258 GPs behind) idle=a8c/0/0
> >>softirq=21608/21608 fqs=0
> >>[240000.066510]         11-...: (1665 GPs behind) idle=8e6/0/0
> >>softirq=18844/18844 fqs=0
> >>[240000.066512]         13-...: (1665 GPs behind) idle=ab8/0/0
> >>softirq=21278/21278 fqs=0
> >>[240000.066515]         14-...: (4854 GPs behind) idle=578/0/0
> >>softirq=25624/25626 fqs=0
> >>[240000.066517]         15-...: (8034 GPs behind) idle=f5e/0/0
> >>softirq=18114/18115 fqs=0
> >>[240000.066520]         16-...: (1665 GPs behind) idle=b66/0/0
> >>softirq=19511/19511 fqs=0
> >>[240000.066528]         17-...: (0 ticks this GP) idle=e18/0/0
> >>softirq=16163/16163 fqs=0
> >>[240000.066531]         18-...: (1665 GPs behind) idle=a18/0/0
> >>softirq=16424/16424 fqs=0
> >>[240000.066533]         19-...: (1665 GPs behind) idle=944/0/0
> >>softirq=17920/17920 fqs=0
> >>[240000.066549]         20-...: (20991 GPs behind) idle=750/0/0
> >>softirq=17549/17552 fqs=0
> >>[240000.066552]         21-...: (0 ticks this GP) idle=9e0/0/0
> >>softirq=18937/18937 fqs=0
> >>[240000.066555]         22-...: (14519 GPs behind) idle=95e/0/0
> >>softirq=16122/16124 fqs=0
> >>[240000.066557]         23-...: (1665 GPs behind) idle=bbc/0/0
> >>softirq=16316/16316 fqs=0
> >>[240000.066560]         24-...: (0 ticks this GP) idle=c56/0/0
> >>softirq=20070/20070 fqs=0
> >>[240000.066563]         27-...: (8034 GPs behind) idle=bdc/0/0
> >>softirq=18291/18292 fqs=0
> >>[240000.066566]         28-...: (8034 GPs behind) idle=4f8/0/0
> >>softirq=22313/22314 fqs=0
> >>[240000.066568]         29-...: (3443 GPs behind) idle=22a/0/0
> >>softirq=24975/24976 fqs=0
> >>[240000.066571]         30-...: (1665 GPs behind) idle=940/0/0
> >>softirq=89382/89382 fqs=0
> >>[240000.066572]         (detected by 10, t=60002 jiffies, g=4843721,
> >>c=4843720, q=659)
> >>[240000.066578] Task dump for CPU 2:
> >>[240000.066581] swapper/2       R  running task        0     0
> >>1 0x00200000
> >>[240000.066588]  0000000000000083 ffffffffa5cecd79 ffff8aca3eea1e00
> >>ffffffffa64cab40
> >>[240000.066593]  0000000000000005 ffffffffa64cad38 ffffa96c80073eb0
> >>ffffffffa5ba9d93
> >>[240000.066597]  ffff8aca3eea1e00 000000000e94fec6 ffff8aca38535940
> >>0000000000000002
> >>[240000.066601] Call Trace:
> >>[240000.066617]  [<ffffffffa5cecd79>] ? intel_idle+0x109/0x110
> >>[240000.066625]  [<ffffffffa5ba9d93>] ?
> >>cpuidle_enter_state+0x103/0x2b0
> >>[240000.066629]  [<ffffffffa5ba9f77>] ? cpuidle_enter+0x17/0x20
> >>[240000.066638]  [<ffffffffa50d5d73>] ? call_cpuidle+0x23/0x40
> >>[240000.066641]  [<ffffffffa50d5fd7>] ? cpu_startup_entry+0x147/0x220
> >>[240000.066647]  [<ffffffffa503ecfd>] ? start_secondary+0x12d/0x140
> >>[240000.066650] Task dump for CPU 3:
> >>[240000.066651] swapper/3       R  running task        0     0
> >>1 0x00200000
> >>
> >>Regards,
> >>Mitko
> >>
>