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Date: Wed, 29 Oct 2014 08:08:31 +0300
From: Kirill Tkhai <ktkhai@...allels.com>
To: Fengguang Wu <fengguang.wu@...el.com>
CC: Peter Zijlstra <peterz@...radead.org>, LKP <lkp@...org>,
<linux-kernel@...r.kernel.org>
Subject: Re: [sched] [ INFO: suspicious RCU usage. ]
Thanks, Fengguang.
I've suggested this patch https://lkml.org/lkml/2014/10/28/41.
В Вт, 28/10/2014 в 22:27 +0800, Fengguang Wu пишет:
> Greetings,
>
> 0day kernel testing robot got the below dmesg and the first bad commit is
>
> git://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git sched/urgent
> commit f6a2b544517d33f6a1e428567bda96fd859ce1c9
> Author: Kirill Tkhai <ktkhai@...allels.com>
> AuthorDate: Mon Oct 27 14:18:25 2014 +0400
> Commit: Peter Zijlstra <peterz@...radead.org>
> CommitDate: Mon Oct 27 13:23:31 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>
> Link: http://lkml.kernel.org/r/1414405105.19914.169.camel@tkhai
>
> +---------------------------+-----------+------------+------------+
> | | v3.18-rc2 | f6a2b54451 | 8e5859c73b |
> +---------------------------+-----------+------------+------------+
> | boot_successes | 200 | 0 | 0 |
> | boot_failures | 1 | 20 | 11 |
> | BUG:kernel_boot_hang | 1 | | |
> | INFO:suspicious_RCU_usage | 0 | 20 | 11 |
> | backtrace:do_fork | 0 | 20 | 11 |
> +---------------------------+-----------+------------+------------+
>
> [ 0.060187]
> [ 0.060500] ===============================
> [ 0.060500] ===============================
> [ 0.061307] [ INFO: suspicious RCU usage. ]
> [ 0.061307] [ INFO: suspicious RCU usage. ]
> [ 0.062109] 3.18.0-rc2-gf6a2b54 #404 Not tainted
> [ 0.062109] 3.18.0-rc2-gf6a2b54 #404 Not tainted
> [ 0.063049] -------------------------------
>
> git bisect start 8e5859c73b9f45602222441a23eba899bb24c82e 522e980064c24d3dd9859e9375e17417496567cf --
> git bisect bad 259820751fd17a4b49098429c68c2c0adfd1c9ed # 21:11 0- 2 Merge branch 'sched/core'
> git bisect bad 8c64bf8de891aa51e916b51a3f7992321ec19b63 # 21:15 0- 1 Merge branch 'sched/urgent'
> git bisect bad fd457f2bafdc4e367d1814ac395035a35980783f # 21:27 0- 7 sched/fair: Care divide error in update_task_scan_period()
> git bisect bad fb5b330f079e243dcc831e9a3d65b9b9fbbed7f8 # 21:36 0- 1 sched/deadline: don't replenish from a !SCHED_DEADLINE entity
> git bisect bad f6a2b544517d33f6a1e428567bda96fd859ce1c9 # 21:41 0- 2 sched: Fix race between task_group and sched_task_group
> # first bad commit: [f6a2b544517d33f6a1e428567bda96fd859ce1c9] sched: Fix race between task_group and sched_task_group
> git bisect good cac7f2429872d3733dc3f9915857b1691da2eb2f # 21:58 60+ 1 Linux 3.18-rc2
> git bisect bad 8e5859c73b9f45602222441a23eba899bb24c82e # 22:00 0- 11 Merge branch 'sched/wait'
> git bisect good cac7f2429872d3733dc3f9915857b1691da2eb2f # 22:05 60+ 1 Linux 3.18-rc2
> git bisect good 7a891e6323e963f3301e44bdeee734028e34d390 # 22:14 60+ 0 Add linux-next specific files for 20141027
>
>
> 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
> -cpu kvm64
> -enable-kvm
> -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
> _______________________________________________
> LKP mailing list
> LKP@...ux.intel.com
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