# rcu_sched detected stalls on CPU/tasks

## BlueFusion

Hello,

I am running gentoo-sources-4.10.3 on multiple machines but on my NAS box, I got the following stack dump from rcu_sched.  I've never seen this before.  It appears multiple times in dmesg on this server from the weekend while I was away.

Doing some research on rcu_sched and stalls, it seems the CPU was "stuck" in a state, too long during some process.  As far as my feable mind can tell, it was stuck on the "swapper" idle process.  This is a fairly idle server, so maybe is it a false positive?

Below the dmesg dump is system info.

```
[422737.116158] INFO: rcu_sched detected stalls on CPUs/tasks:

[422737.116165]         9-...: (95 GPs behind) idle=b3a/0/0 softirq=37283/37283 fqs=0 

[422737.116168]         10-...: (168 GPs behind) idle=d52/0/0 softirq=34914/34915 fqs=0 

[422737.116170]         11-...: (504 GPs behind) idle=e02/0/0 softirq=33227/33227 fqs=0 

[422737.116172]         12-...: (0 ticks this GP) idle=5ea/0/0 softirq=143335/143335 fqs=0 

[422737.116174]         13-...: (270 GPs behind) idle=184/0/0 softirq=191637/191638 fqs=0 

[422737.116177]         18-...: (0 ticks this GP) idle=c76/0/0 softirq=34101/34101 fqs=0 

[422737.116179]         19-...: (95 GPs behind) idle=132/0/0 softirq=35621/35621 fqs=0 

[422737.116181]         20-...: (0 ticks this GP) idle=a24/0/0 softirq=37196/37196 fqs=0 

[422737.116183]         21-...: (95 GPs behind) idle=e00/0/0 softirq=36790/36790 fqs=0 

[422737.116185]         22-...: (0 ticks this GP) idle=10a/0/0 softirq=32949/32949 fqs=0 

[422737.116186]         (detected by 23, t=60002 jiffies, g=1053391, c=1053390, q=1470)

[422737.116189] Task dump for CPU 9:

[422737.116191] swapper/9       R  running task        0     0      1 0x00200000

[422737.116194] Call Trace:

[422737.116205]  ? cpuidle_enter_state+0xe3/0x1b0

[422737.116212]  ? do_idle+0x167/0x1c0

[422737.116214]  ? cpu_startup_entry+0x68/0x70

[422737.116219]  ? start_secondary+0x138/0x160

[422737.116221]  ? start_cpu+0x14/0x14

[422737.116222] Task dump for CPU 10:

[422737.116223] swapper/10      R  running task        0     0      1 0x00200000

[422737.116225] Call Trace:

[422737.116228]  ? cpuidle_enter_state+0xe3/0x1b0

[422737.116230]  ? do_idle+0x167/0x1c0

[422737.116232]  ? cpu_startup_entry+0x68/0x70

[422737.116234]  ? start_secondary+0x138/0x160

[422737.116235]  ? start_cpu+0x14/0x14

[422737.116236] Task dump for CPU 11:

[422737.116237] swapper/11      R  running task        0     0      1 0x00200000

[422737.116239] Call Trace:

[422737.116241]  ? cpuidle_enter_state+0xe3/0x1b0

[422737.116243]  ? do_idle+0x167/0x1c0

[422737.116245]  ? cpu_startup_entry+0x68/0x70

[422737.116247]  ? start_secondary+0x138/0x160

[422737.116248]  ? start_cpu+0x14/0x14

[422737.116249] Task dump for CPU 12:

[422737.116250] swapper/12      R  running task        0     0      1 0x00200000

[422737.116252] Call Trace:

[422737.116254]  ? cpuidle_enter_state+0xe3/0x1b0

[422737.116256]  ? do_idle+0x167/0x1c0

[422737.116258]  ? cpu_startup_entry+0x68/0x70

[422737.116260]  ? start_secondary+0x138/0x160

[422737.116261]  ? start_cpu+0x14/0x14

[422737.116262] Task dump for CPU 13:

[422737.116263] swapper/13      R  running task        0     0      1 0x00200000

[422737.116265] Call Trace:

[422737.116267]  ? cpuidle_enter_state+0xe3/0x1b0

[422737.116269]  ? do_idle+0x167/0x1c0

[422737.116271]  ? cpu_startup_entry+0x68/0x70

[422737.116273]  ? start_secondary+0x138/0x160

[422737.116277]  ? start_cpu+0x14/0x14

[422737.116278] Task dump for CPU 18:

[422737.116279] swapper/18      R  running task        0     0      1 0x00200000

[422737.116280] Call Trace:

[422737.116281]  ? cpuidle_enter_state+0xe3/0x1b0

[422737.116283]  ? do_idle+0x167/0x1c0

[422737.116284]  ? cpu_startup_entry+0x68/0x70

[422737.116285]  ? start_secondary+0x138/0x160

[422737.116286]  ? start_cpu+0x14/0x14

[422737.116287] Task dump for CPU 19:

[422737.116287] swapper/19      R  running task        0     0      1 0x00200000

[422737.116288] Call Trace:

[422737.116290]  ? cpuidle_enter_state+0xe3/0x1b0

[422737.116291]  ? do_idle+0x167/0x1c0

[422737.116293]  ? cpu_startup_entry+0x68/0x70

[422737.116294]  ? start_secondary+0x138/0x160

[422737.116295]  ? start_cpu+0x14/0x14

[422737.116295] Task dump for CPU 20:

[422737.116296] swapper/20      R  running task        0     0      1 0x00200000

[422737.116297] Call Trace:

[422737.116298]  ? cpuidle_enter_state+0xe3/0x1b0

[422737.116300]  ? do_idle+0x167/0x1c0

[422737.116301]  ? cpu_startup_entry+0x68/0x70

[422737.116302]  ? start_secondary+0x138/0x160

[422737.116303]  ? start_cpu+0x14/0x14

[422737.116304] Task dump for CPU 21:

[422737.116304] swapper/21      R  running task        0     0      1 0x00200000

[422737.116305] Call Trace:

[422737.116307]  ? cpuidle_enter_state+0xe3/0x1b0

[422737.116308]  ? do_idle+0x167/0x1c0

[422737.116310]  ? cpu_startup_entry+0x68/0x70

[422737.116311]  ? start_secondary+0x138/0x160

[422737.116312]  ? start_cpu+0x14/0x14

[422737.116312] Task dump for CPU 22:

[422737.116313] swapper/22      R  running task        0     0      1 0x00200000

[422737.116314] Call Trace:

[422737.116315]  ? cpuidle_enter_state+0xe3/0x1b0

[422737.116317]  ? do_idle+0x167/0x1c0

[422737.116318]  ? cpu_startup_entry+0x68/0x70

[422737.116319]  ? start_secondary+0x138/0x160

[422737.116320]  ? start_cpu+0x14/0x14

[422737.116322] rcu_sched kthread starved for 60002 jiffies! g1053391 c1053390 f0x0 RCU_GP_WAIT_FQS(3) ->state=0x1

[422737.116322] rcu_sched       S    0     7      2 0x00000000

[422737.116324] Call Trace:

[422737.116328]  ? __schedule+0x178/0x550

[422737.116330]  ? schedule+0x2d/0x80

[422737.116332]  ? schedule_timeout+0x169/0x240

[422737.116336]  ? del_timer_sync+0x50/0x50

[422737.116339]  ? cpu_needs_another_gp+0x80/0x80

[422737.116341]  ? rcu_gp_kthread+0x3a8/0x7c0

[422737.116344]  ? kthread+0xea/0x120

[422737.116345]  ? force_qs_rnp+0x170/0x170

[422737.116346]  ? kthread_park+0x80/0x80

[422737.116349]  ? ret_from_fork+0x23/0x30
```

```
neutron ~ # emerge --info

Portage 2.3.3 (python 3.4.5-final-0, default/linux/amd64/13.0, gcc-4.9.4, glibc-2.23-r3, 4.10.3-gentoo x86_64)

=================================================================

System uname: Linux-4.10.3-gentoo-x86_64-Intel-R-_Xeon-R-_CPU_E5645_@_2.40GHz-with-gentoo-2.3

KiB Mem:    74099464 total,  51794972 free

KiB Swap:          0 total,         0 free

Timestamp of repository gentoo: Thu, 16 Mar 2017 16:00:01 +0000

sh bash 4.3_p48-r1

ld GNU ld (Gentoo 2.26.1 p1.0) 2.26.1

app-shells/bash:          4.3_p48-r1::gentoo

dev-lang/perl:            5.22.3_rc4::gentoo

dev-lang/python:          2.7.12::gentoo, 3.4.5::gentoo

dev-util/cmake:           3.7.2::gentoo

dev-util/pkgconfig:       0.28-r2::gentoo

sys-apps/baselayout:      2.3::gentoo

sys-apps/openrc:          0.23.2::gentoo

sys-apps/sandbox:         2.10-r3::gentoo

sys-devel/autoconf:       2.69::gentoo

sys-devel/automake:       1.14.1::gentoo, 1.15::gentoo

sys-devel/binutils:       2.26.1::gentoo

sys-devel/gcc:            4.9.4::gentoo

sys-devel/gcc-config:     1.7.3::gentoo

sys-devel/libtool:        2.4.6-r3::gentoo

sys-devel/make:           4.2.1::gentoo

sys-kernel/linux-headers: 4.4::gentoo (virtual/os-headers)

sys-libs/glibc:           2.23-r3::gentoo

Repositories:

gentoo

    location: /usr/portage

    sync-type: rsync

    sync-uri: rsync://atom/gentoo-portage

    priority: -1000

ACCEPT_KEYWORDS="amd64"

ACCEPT_LICENSE="* -@EULA"

CBUILD="x86_64-pc-linux-gnu"

CFLAGS="-march=westmere -O2 -pipe"

CHOST="x86_64-pc-linux-gnu"

CONFIG_PROTECT="/etc"

CONFIG_PROTECT_MASK="/etc/ca-certificates.conf /etc/env.d /etc/gconf /etc/gentoo-release /etc/revdep-rebuild /etc/sandbox.d /etc/terminfo"

CXXFLAGS="-march=westmere -O2 -pipe"

DISTDIR="/usr/portage/distfiles"

FCFLAGS="-O2 -pipe"

FEATURES="assume-digests binpkg-logs config-protect-if-modified distlocks ebuild-locks fixlafiles getbinpkg merge-sync news parallel-fetch preserve-libs protect-owned sandbox sfperms strict unknown-features-warn unmerge-logs unmerge-orphans userfetch userpriv usersandbox usersync xattr"

FFLAGS="-O2 -pipe"

GENTOO_MIRRORS="http://distfiles.gentoo.org"

LANG="en_US.UTF-8"

LDFLAGS="-Wl,-O1 -Wl,--as-needed"

MAKEOPTS="-j24"

PKGDIR="/usr/portage/packages"

PORTAGE_CONFIGROOT="/"

PORTAGE_RSYNC_OPTS="--recursive --links --safe-links --perms --times --omit-dir-times --compress --force --whole-file --delete --stats --human-readable --timeout=180 --exclude=/distfiles --exclude=/local --exclude=/packages --exclude=/.git"

PORTAGE_TMPDIR="/var/tmp"

USE="acl amd64 berkdb bzip2 cli cracklib crypt cxx dri fortran gdbm iconv ipv6 ldap lzo modules multilib ncurses nls nptl ntp openmp pam pcre readline samba seccomp session spice ssl tcpd udev unicode usb usbredir virt-network xattr xfs zlib" ABI_X86="32 64" ALSA_CARDS="ali5451 als4000 atiixp atiixp-modem bt87x ca0106 cmipci emu10k1x ens1370 ens1371 es1938 es1968 fm801 hda-intel intel8x0 intel8x0m maestro3 trident usb-audio via82xx via82xx-modem ymfpci" APACHE2_MODULES="authn_core authz_core socache_shmcb unixd actions alias auth_basic authn_alias authn_anon authn_dbm authn_default authn_file authz_dbm authz_default authz_groupfile authz_host authz_owner authz_user autoindex cache cgi cgid dav dav_fs dav_lock deflate dir disk_cache env expires ext_filter file_cache filter headers include info log_config logio mem_cache mime mime_magic negotiation rewrite setenvif speling status unique_id userdir usertrack vhost_alias" CALLIGRA_FEATURES="kexi words flow plan sheets stage tables krita karbon braindump author" COLLECTD_PLUGINS="df interface irq load memory rrdtool swap syslog" CPU_FLAGS_X86="aes mmx mmxext popcnt sse sse2 sse3 sse4_1 sse4_2 ssse3" ELIBC="glibc" GPSD_PROTOCOLS="ashtech aivdm earthmate evermore fv18 garmin garmintxt gpsclock isync itrax mtk3301 nmea ntrip navcom oceanserver oldstyle oncore rtcm104v2 rtcm104v3 sirf skytraq superstar2 timing tsip tripmate tnt ublox ubx" INPUT_DEVICES="libinput keyboard mouse" KERNEL="linux" L10N="en en_US" LCD_DEVICES="bayrad cfontz cfontz633 glk hd44780 lb216 lcdm001 mtxorb ncurses text" LIBREOFFICE_EXTENSIONS="presenter-console presenter-minimizer" LINGUAS="en en_US" OFFICE_IMPLEMENTATION="libreoffice" PHP_TARGETS="php5-6" PYTHON_SINGLE_TARGET="python2_7" PYTHON_TARGETS="python2_7 python3_4" RUBY_TARGETS="ruby21" USERLAND="GNU" VIDEO_CARDS="amdgpu fbdev intel nouveau radeon radeonsi vesa dummy v4l" XTABLES_ADDONS="quota2 psd pknock lscan length2 ipv4options ipset ipp2p iface geoip fuzzy condition tee tarpit sysrq steal rawnat logmark ipmark dhcpmac delude chaos account"

Unset:  CC, CPPFLAGS, CTARGET, CXX, EMERGE_DEFAULT_OPTS, INSTALL_MASK, LC_ALL, PORTAGE_BUNZIP2_COMMAND, PORTAGE_COMPRESS, PORTAGE_COMPRESS_FLAGS, PORTAGE_RSYNC_EXTRA_OPTS, USE_PYTHON
```

It's running on a Supermicro X8DTN+ motherboard.  The faulty 5520 chipset interrupt remapping is also diabled with intel_iommu=on intremap=off.

[Moderator edit: changed [quote] tags to [code] tags to preserve output layout. -Hu]

----------

## Plumbo

Hi,

I've also experienced these stalls after long periods of inactivity on my systems. They started to appear when I upgraded to the 4.10 kernel, but they disappeared around 4.10.5 or 4.10.6.

I never found the cause, but an upgrade to > 4.10.5 might solve it.

----------

## BlueFusion

I forgot to update this, but you are right.  After updating to 4.10.5 this went away.

----------

## soloslinger

Posting here in case this helps someone else.

With the Gentoo minimal ISO from January (2017), I could reproduce this on every attempt to install on a Thinkpad T460p purchased in December (2016).  I didn't check the ISO, but I did reimage my boot media with it several times & switched up USB sticks.  I hadn't quite gotten around to attempting with sysrescuecd, because I'm not that familiar with it and was getting various distances into the install depending on whether I was using MBR or GPT partitions.  ( Which, didn't make a whole lot of sense to me either and I'm still clumsy with GPT & UEFI. )

I found this thread and with the May minimal ISO, I sailed through the install.

Hopefully this helps someone else.

soloslinger

----------

## krinn

good info

good spirit

thank you soloslinger

----------

