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Date: Sun, 1 Feb 2015 20:22:35 -0800
From: Fengguang Wu <fengguang.wu@...el.com>
To: Kirill Tkhai <ktkhai@...allels.com>
Cc: Ingo Molnar <mingo@...nel.org>, LKP <lkp@...org>,
linux-kernel@...r.kernel.org
Subject: [sched] [ INFO: suspicious RCU usage. ]
Hi Kirill,
FYI the RCU warning shows up since this commit, however there are
several other BUGs, so it's not necessarily a problem of this patch.
commit eeb61e53ea19be0c4015b00b2e8b3b2185436f2b
Author: Kirill Tkhai <ktkhai@...allels.com>
AuthorDate: Mon Oct 27 14:18:25 2014 +0400
Commit: Ingo Molnar <mingo@...nel.org>
CommitDate: Tue Oct 28 10:45:59 2014 +0100
sched: Fix race between task_group and sched_task_group
The race may happen when somebody is changing task_group of a forking task.
Child's cgroup is the same as parent's after dup_task_struct() (there just
memory copying). Also, cfs_rq and rt_rq are the same as parent's.
But if parent changes its task_group before it's called cgroup_post_fork(),
we do not reflect this situation on child. Child's cfs_rq and rt_rq remain
the same, while child's task_group changes in cgroup_post_fork().
To fix this we introduce fork() method, which calls sched_move_task() directly.
This function changes sched_task_group on appropriate (also its logic has
no problem with freshly created tasks, so we shouldn't introduce something
special; we are able just to use it).
Possibly, this decides the Burke Libbey's problem: https://lkml.org/lkml/2014/10/24/456
Signed-off-by: Kirill Tkhai <ktkhai@...allels.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Link: http://lkml.kernel.org/r/1414405105.19914.169.camel@tkhai
Signed-off-by: Ingo Molnar <mingo@...nel.org>
===================================================
PARENT COMMIT NOT CLEAN. LOOK OUT FOR WRONG BISECT!
===================================================
Attached dmesg for the parent commit, too, to help confirm whether it is a noise error.
+--------------------------------------------------------+------------+------------+------------+
| | xfs-for-li | eeb61e53ea | 28ff344e1d |
+--------------------------------------------------------+------------+------------+------------+
| boot_successes | 0 | 0 | 0 |
| boot_failures | 60 | 20 | 11 |
| WARNING:at_include/linux/kref.h:#kobject_get() | 60 | 20 | 11 |
| WARNING:at_fs/kernfs/dir.c:#kernfs_remove_by_name_ns() | 1 | 1 | 1 |
| BUG:unable_to_handle_kernel | 59 | 20 | 11 |
| Oops | 59 | 20 | 11 |
| RIP:string | 1 | 1 | 1 |
| Kernel_panic-not_syncing:Fatal_exception | 59 | 20 | 11 |
| backtrace:platform_driver_unregister | 60 | 20 | 11 |
| backtrace:init_mac80211_hwsim | 60 | 20 | 11 |
| backtrace:kernel_init_freeable | 60 | 20 | 11 |
| backtrace:bus_register | 1 | 1 | 1 |
| backtrace:i2o_driver_init | 1 | 1 | 1 |
| backtrace:i2o_iop_init | 1 | 1 | 1 |
| INFO:trying_to_register_non-static_key | 59 | 18 | 10 |
| RIP:mutex_lock_nested | 58 | 18 | 10 |
| INFO:rcu_sched_detected_stalls_on_CPUs/tasks | 1 | | |
| INFO:task_blocked_for_more_than#seconds | 1 | | |
| INFO:lockdep_is_turned_off | 1 | | |
| RIP:native_apic_mem_write | 1 | | |
| RIP:rep_nop | 1 | | |
| Kernel_panic-not_syncing:hung_task:blocked_tasks | 1 | | |
| backtrace:ring_buffer_producer_thread | 1 | | |
| backtrace:watchdog | 1 | | |
| INFO:suspicious_RCU_usage | 0 | 20 | 11 |
| WARNING:at_kernel/locking/lockdep.c:#__bfs() | 0 | 1 | |
| RIP:__bfs | 0 | 1 | |
| backtrace:do_fork | 0 | 20 | 11 |
+--------------------------------------------------------+------------+------------+------------+
[ 0.014295] debug: unmapping init [mem 0xffffffff82820000-0xffffffff82823fff]
[ 0.017254]
[ 0.017433] ===============================
[ 0.017885] [ INFO: suspicious RCU usage. ]
[ 0.018000] 3.18.0-rc2-00001-geeb61e5 #6 Not tainted
[ 0.018000] -------------------------------
[ 0.018000] kernel/sched/core.c:7408 suspicious rcu_dereference_check() usage!
[ 0.018000]
[ 0.018000] other info that might help us debug this:
[ 0.018000]
[ 0.018000]
[ 0.018000] rcu_scheduler_active = 1, debug_locks = 1
[ 0.018000] 2 locks held by swapper/0/0:
[ 0.018000] #0: (&p->pi_lock){......}, at: [<ffffffff810dbbdf>] task_rq_lock+0x38/0xe7
[ 0.018000] #1: (&rq->lock){-.....}, at: [<ffffffff810dbbfa>] task_rq_lock+0x53/0xe7
[ 0.018000]
[ 0.018000] stack backtrace:
[ 0.018000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.18.0-rc2-00001-geeb61e5 #6
[ 0.018000] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[ 0.018000] 0000000000000001 ffffffff82403cc8 ffffffff81b9e83f ffffffff82425580
[ 0.018000] 0000000000000001 ffffffff82403cf8 ffffffff810f3d12 ffff880012068000
[ 0.018000] ffff880012422040 0000000000000000 0000000000000000 ffffffff82403d58
[ 0.018000] Call Trace:
[ 0.018000] [<ffffffff81b9e83f>] dump_stack+0x51/0xaa
[ 0.018000] [<ffffffff810f3d12>] lockdep_rcu_suspicious+0xfa/0x103
[ 0.018000] [<ffffffff810e2c04>] sched_move_task+0xe5/0x153
[ 0.018000] [<ffffffff810e2c8f>] cpu_cgroup_fork+0x9/0xb
[ 0.018000] [<ffffffff81131f85>] cgroup_post_fork+0x9b/0xaa
[ 0.018000] [<ffffffff810ba1f0>] copy_process+0x178a/0x18bf
[ 0.018000] [<ffffffff81b9776c>] ? rest_init+0x130/0x130
[ 0.018000] [<ffffffff8119f86c>] ? vm_unmap_aliases+0x196/0x1a5
[ 0.018000] [<ffffffff810ba4ff>] do_fork+0xec/0x3e1
[ 0.018000] [<ffffffff81b9776c>] ? rest_init+0x130/0x130
[ 0.018000] [<ffffffff810ba815>] kernel_thread+0x21/0x23
[ 0.018000] [<ffffffff81b9765a>] rest_init+0x1e/0x130
[ 0.018000] [<ffffffff82728f3c>] start_kernel+0x433/0x440
[ 0.018000] [<ffffffff82728120>] ? early_idt_handlers+0x120/0x120
[ 0.018000] [<ffffffff827284cb>] x86_64_start_reservations+0x2a/0x2c
[ 0.018000] [<ffffffff82728608>] x86_64_start_kernel+0x13b/0x14a
[ 0.018079] Getting VERSION: 1050014
[ 0.019012] Getting VERSION: 1050014
[ 0.019403] Getting ID: 0
git bisect start 5e62863aea463c9bf24538315327d0922be35d64 v3.17 --
git bisect good f207671f402b9aa7367ee21dbab2e450d16c9d7e # 01:43 20+ 20 staging: unisys: refactor ULTRA_DIAG_CHANNEL_PROTOCOL
git bisect good 7c0496d19159df8b5a537154194a75dcdfca873a # 01:50 20+ 20 staging: vt6655: mac80211 conversion: s_vFillRTSHead convert to using struct ieee80211_hdr
git bisect bad 33192fa1d173b91ba98c29cb8ab414c76ae3ff0b # 01:53 0- 20 staging: unisys: refactor VISORCHIPSET_BUS_INFO
git bisect good 146761058f63d8530d150bef00c1d3daaa53dbba # 01:58 20+ 20 staging: vt6655: struct vnt_private remove dead members
git bisect good 037a449ac71fc5c70d2b0af28ce6792065daae55 # 02:04 20+ 20 staging: rtl8188eu: os_dep: Remove useless cast on void pointer
git bisect good 425ebd0aa35dcfc5fe2449ef3e1194e422f6f9b4 # 02:14 20+ 20 staging: unisys: virtpci: Add a blank line after the definition of driver_private
git bisect good 9056be30542bfff51190bdda67088f319cf4c9f5 # 02:20 20+ 20 Staging: lustre: lnet: lnet: Better cookie gen
git bisect bad 2c683cde06c1d57a9ecbacc484540e259e7255fa # 02:26 0- 20 staging: unisys: refactor CRASH_OBJ_TYPE
git bisect bad 37951dabd899587afc31ddd508b9cdddc9c24524 # 02:33 0- 20 staging: unisys: get rid of VISORCHIPSET_STATE typedef
git bisect bad 7cbe010a5ea728d7c4440b11a1a3997faca0e46d # 02:40 0- 20 Merge 3.18-rc3 into staging-next
git bisect good f7e87a44ef60ad379e39b45437604141453bf0ec # 02:48 20+ 20 Merge tag 'media/v3.18-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media
git bisect bad 89453379aaf0608253124057df6cd8ac63948135 # 02:56 0- 20 Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net
git bisect bad 19e0d5f16ad9759d92f5739b53acdebfe22fa2a2 # 03:04 0- 20 Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
git bisect good 94712927d06c19b785bae92db07ef84b89f156c8 # 03:11 20+ 20 Merge tag 'sound-3.18-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound
git bisect good aea4869f68b5869afbb308bfb7d777d725df8900 # 03:14 20+ 20 Merge branch 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
git bisect good 5656b408ff2696551c0f572689edcad3113e3a32 # 03:17 20+ 20 Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
git bisect good d1cd1210834649ce1ca6bafe5ac25d2f40331343 # 03:31 20+ 20 x86, pageattr: Prevent overflow in slow_virt_to_phys() for X86_PAE
git bisect bad 2847c90e1b3ae95379af24894fc4f98e7f2fd705 # 03:34 0- 20 sched/fair: Care divide error in update_task_scan_period()
git bisect bad 64be6f1f5f710f5995d41caf8a1767fe6d2b5a87 # 03:37 0- 20 sched/deadline: Don't replenish from a !SCHED_DEADLINE entity
git bisect bad eeb61e53ea19be0c4015b00b2e8b3b2185436f2b # 03:39 0- 20 sched: Fix race between task_group and sched_task_group
# first bad commit: [eeb61e53ea19be0c4015b00b2e8b3b2185436f2b] sched: Fix race between task_group and sched_task_group
git bisect good cac7f2429872d3733dc3f9915857b1691da2eb2f # 03:45 60+ 60 Linux 3.18-rc2
# extra tests with DEBUG_INFO
git bisect good eeb61e53ea19be0c4015b00b2e8b3b2185436f2b # 03:52 60+ 49 sched: Fix race between task_group and sched_task_group
# extra tests on HEAD of next/master
git bisect good 827e3bdf1bb2401c1a1e5586eb3977d228d298b2 # 03:59 60+ 0 Add linux-next specific files for 20150130
# extra tests on tree/branch linus/master
git bisect bad 788807d7ca3821b5ea835a588a52d55631c17e18 # 04:01 58- 3 Merge branch 'i2c/for-current' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux
# extra tests with first bad commit reverted
# extra tests on tree/branch linus/master
git bisect bad 788807d7ca3821b5ea835a588a52d55631c17e18 # 04:03 0- 3 Merge branch 'i2c/for-current' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux
# extra tests on tree/branch next/master
git bisect bad 827e3bdf1bb2401c1a1e5586eb3977d228d298b2 # 04:07 295- 40 Add linux-next specific files for 20150130
This script may reproduce the error.
----------------------------------------------------------------------------
#!/bin/bash
kernel=$1
initrd=quantal-core-x86_64.cgz
wget --no-clobber https://github.com/fengguang/reproduce-kernel-bug/raw/master/initrd/$initrd
kvm=(
qemu-system-x86_64
-enable-kvm
-cpu Haswell,+smep,+smap
-kernel $kernel
-initrd $initrd
-m 320
-smp 2
-net nic,vlan=1,model=e1000
-net user,vlan=1
-boot order=nc
-no-reboot
-watchdog i6300esb
-rtc base=localtime
-serial stdio
-display none
-monitor null
)
append=(
hung_task_panic=1
earlyprintk=ttyS0,115200
debug
apic=debug
sysrq_always_enabled
rcupdate.rcu_cpu_stall_timeout=100
panic=-1
softlockup_panic=1
nmi_watchdog=panic
oops=panic
load_ramdisk=2
prompt_ramdisk=0
console=ttyS0,115200
console=tty0
vga=normal
root=/dev/ram0
rw
drbd.minor_count=8
)
"${kvm[@]}" --append "${append[*]}"
----------------------------------------------------------------------------
Thanks,
Fengguang
View attachment "dmesg-quantal-kbuild-26:20150202033610:x86_64-randconfig-c2-0201:3.18.0-rc2-00001-geeb61e5:6" of type "text/plain" (51742 bytes)
View attachment "dmesg-quantal-ivb41-102:20150202034009:x86_64-randconfig-c2-0201:3.18.0-rc2:7" of type "text/plain" (51038 bytes)
View attachment "config-3.18.0-rc2-00001-geeb61e5" of type "text/plain" (85583 bytes)
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