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Date: Mon, 3 Nov 2014 22:53:32 +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. ]
Greetings,
0day kernel testing robot got the below dmesg and the first bad commit is
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
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>
+------------------------------------------------+-----------+------------+---------------+
| | v3.18-rc2 | eeb61e53ea | next-20141031 |
+------------------------------------------------+-----------+------------+---------------+
| boot_successes | 60 | 0 | 0 |
| boot_failures | 0 | 20 | 11 |
| INFO:suspicious_RCU_usage | 0 | 20 | 11 |
| backtrace:do_fork | 0 | 20 | 11 |
| WARNING:at_kernel/sched/core.c:__might_sleep() | 0 | 0 | 11 |
| backtrace:rfcomm_run | 0 | 0 | 11 |
| WARNING:CPU:#PID:#at/kbuild/src/smo | 0 | 0 | 1 |
| BUG:kernel_boot_hang | 0 | 0 | 1 |
+------------------------------------------------+-----------+------------+---------------+
[ 0.086529] debug: unmapping init [mem 0xffffffff82607000-0xffffffff82609fff]
[ 0.090115]
[ 0.090782] ===============================
[ 0.091842] [ INFO: suspicious RCU usage. ]
[ 0.092000] 3.18.0-rc2-00001-geeb61e5 #7 Not tainted
[ 0.092000] -------------------------------
[ 0.092000] kernel/sched/core.c:7408 suspicious rcu_dereference_check() usage!
[ 0.092000]
[ 0.092000] other info that might help us debug this:
[ 0.092000]
[ 0.092000]
[ 0.092000] rcu_scheduler_active = 1, debug_locks = 0
[ 0.092000] 2 locks held by swapper/0/0:
[ 0.092000] #0: (&p->pi_lock){......}, at: [<ffffffff810b8d96>] task_rq_lock+0x30/0xaa
[ 0.092000] #1: (&rq->lock){-.....}, at: [<ffffffff810b8db8>] task_rq_lock+0x52/0xaa
[ 0.092000]
[ 0.092000] stack backtrace:
[ 0.092000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.18.0-rc2-00001-geeb61e5 #7
[ 0.092000] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[ 0.092000] 0000000000000001 ffffffff819dbcb8 ffffffff815e2acd 000000000000182c
[ 0.092000] ffffffff819f85c0 ffffffff819dbce8 ffffffff810d1774 ffff880013510000
[ 0.092000] ffff8800139de180 ffff880013528000 0000000000800300 ffffffff819dbd48
[ 0.092000] Call Trace:
[ 0.092000] [<ffffffff815e2acd>] dump_stack+0x4e/0x68
[ 0.092000] [<ffffffff810d1774>] lockdep_rcu_suspicious+0x107/0x110
[ 0.092000] [<ffffffff810bf887>] sched_move_task+0xda/0x17b
[ 0.092000] [<ffffffff810bf945>] cpu_cgroup_fork+0x9/0xb
[ 0.092000] [<ffffffff8110c301>] cgroup_post_fork+0x9b/0xaa
[ 0.092000] [<ffffffff8109c1bd>] copy_process+0x17e5/0x1832
[ 0.092000] [<ffffffff815def62>] ? rest_init+0x136/0x136
[ 0.092000] [<ffffffff8109c367>] do_fork+0x8a/0x243
[ 0.092000] [<ffffffff8109c541>] kernel_thread+0x21/0x23
[ 0.092000] [<ffffffff815dee4a>] rest_init+0x1e/0x136
[ 0.092000] [<ffffffff82520fb5>] start_kernel+0x4ba/0x4c7
[ 0.092000] [<ffffffff82520120>] ? early_idt_handlers+0x120/0x120
[ 0.092000] [<ffffffff825204de>] x86_64_start_reservations+0x2a/0x2c
[ 0.092000] [<ffffffff825205e6>] x86_64_start_kernel+0x106/0x115
[ 0.096042] Getting VERSION: 1050014
[ 0.097061] Getting VERSION: 1050014
[ 0.098000] Getting ID: 0
git bisect start 4fbe40970dc154aaeeda0584aab8913fc073127b cac7f2429872d3733dc3f9915857b1691da2eb2f --
git bisect good fd2e6bbbe5b2e8f6d8ea6a28b614ec5c1c8b5a62 # 23:14 20+ 0 Merge remote-tracking branch 'hwmon-staging/hwmon-next'
git bisect good ab6af24617af5f94df5185611f1eb39432d49292 # 01:33 20+ 0 Merge remote-tracking branch 'spi/for-next'
git bisect bad f5ef810eb87c283118797ea33778c5b3c937ad29 # 02:08 0- 3 Merge remote-tracking branch 'staging/staging-next'
git bisect bad 50247251e8b6078b491b5fb54dc31c24867f5930 # 02:47 0- 9 Merge remote-tracking branch 'rcu/rcu/next'
git bisect bad 6a91cd724c20352f8cdc2a73c0649bae71897ed8 # 03:27 0- 7 Merge remote-tracking branch 'edac-amd/for-next'
git bisect bad d7a8d245f2ffb9adde1a7121e5ab86eed8d03584 # 03:39 0- 4 Merge remote-tracking branch 'tip/auto-latest'
git bisect good 26c2d2b39128adba276d140eefa2745591b88536 # 09:46 20+ 0 i386/audit: stop scribbling on the stack frame
git bisect bad 3427445afd26bd2395f29241319283a93f362cd0 # 11:03 0- 1 sched: Exclude cond_resched() from nested sleep test
git bisect bad 1a43a14a5bd9c32dbd7af35e35a5afa703944bcb # 11:39 0- 2 sched: Fix schedule_tail() to disable preemption
git bisect bad f3a7e1a9c464a32ee186ab91388313c82e7ce018 # 12:38 0- 1 sched/dl: Fix preemption checks
git bisect bad 1effd9f19324efb05fccc7421530e11a52db0278 # 12:55 0- 1 sched/numa: Fix unsafe get_task_struct() in task_numa_assign()
git bisect bad 64be6f1f5f710f5995d41caf8a1767fe6d2b5a87 # 15:30 0- 3 sched/deadline: Don't replenish from a !SCHED_DEADLINE entity
git bisect bad eeb61e53ea19be0c4015b00b2e8b3b2185436f2b # 17:18 0- 1 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 # 17:31 60+ 0 Linux 3.18-rc2
git bisect bad 4fbe40970dc154aaeeda0584aab8913fc073127b # 17:31 0- 11 Add linux-next specific files for 20141031
git bisect bad 0df1f2487d2f0d04703f142813d53615d62a1da4 # 20:17 0- 3 Linux 3.18-rc3
git bisect bad a641d0e16b552f986e8c4a8735e66a1443a769cf # 21:44 0- 3 Add linux-next specific files for 20141103
This script may reproduce the error.
----------------------------------------------------------------------------
#!/bin/bash
kernel=$1
initrd=yocto-minimal-x86_64.cgz
wget --no-clobber https://github.com/fengguang/reproduce-kernel-bug/raw/master/initrd/$initrd
kvm=(
qemu-system-x86_64
-enable-kvm
-cpu Haswell,+smep,+smap
-kernel $kernel
-initrd $initrd
-m 320
-smp 1
-net nic,vlan=1,model=e1000
-net user,vlan=1
-boot order=nc
-no-reboot
-watchdog i6300esb
-rtc base=localtime
-serial stdio
-display none
-monitor null
)
append=(
hung_task_panic=1
earlyprintk=ttyS0,115200
debug
apic=debug
sysrq_always_enabled
rcupdate.rcu_cpu_stall_timeout=100
panic=-1
softlockup_panic=1
nmi_watchdog=panic
oops=panic
load_ramdisk=2
prompt_ramdisk=0
console=ttyS0,115200
console=tty0
vga=normal
root=/dev/ram0
rw
drbd.minor_count=8
)
"${kvm[@]}" --append "${append[*]}"
----------------------------------------------------------------------------
Thanks,
Fengguang
View attachment "dmesg-yocto-kbuild-8:20141103171642:x86_64-randconfig-r0-11011222:3.18.0-rc2-00001-geeb61e5:7" of type "text/plain" (53602 bytes)
View attachment "config-3.18.0-rc2-00001-geeb61e5" of type "text/plain" (88373 bytes)
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