[Bug 693594] Re: cgroup-bin should not move kthreadd into a default cgroup

Serge Hallyn 693594 at bugs.launchpad.net
Sat Mar 3 15:03:09 UTC 2012


Jon,

if you could do these soon in the Debian package, I think we should
still be able to get it into precise.

Rioting_Pacifst,

note that we generally recommend using cgroup-lite when possible.

Quoting Rioting_Pacifst (693594 at bugs.launchpad.net):
> This bug has quite a few nasty symptoms (breaks suspend on SMP machines,
> etc) and I guess cgroups are going to get more popular as people try the
> "superpatch" so could we get one of the following into 12.04 please:
> 
> 1)do not move all tasks into a default cgroup 
> comment CREATE_DEFAULT=yes out and uncomment CREATE_DEFAULT=no in /etc/default/cgconfig
> 
> 2)putting the following in /etc/cgconfig.conf
> group sysdefault {
>     cpu {
>         cpu.rt_runtime_us = 950000;
>     }
> }
> 
> 3) Add a rule so that [kthreadd] is never put in the default group
> 
> 4) Changing startup script to not move ktreadadd
> 
> I think creating a superflous default group is stupid anyway so the
> first fix is by far the best.
> 
> Upstream have also release 0.38 but nothing in the changelog seems
> relevant.
> 
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> You received this bug notification because you are subscribed to
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> https://bugs.launchpad.net/bugs/693594
> 
> Title:
>   cgroup-bin should not move kthreadd into a default cgroup
> 
> Status in “libcgroup” package in Ubuntu:
>   Confirmed
> 
> Bug description:
>   Steps to reproduce:
>   1. Install cgroup-bin from universe on a stock Lucid machine (I've only tested amd64, but I suspect it shouldn't matter)
>   2. Load an arbitrary module (e.g. modprobe rds)
>   3. Unload the module loaded in (2) (e.g. rmmod rds)
> 
>   The 'rmmod' process will hang unkillably in the kernel.
> 
>   Here's an example `dmesg` output from the hung-task watchdog for
>   rmmod:
> 
>    INFO: task rmmod:1608 blocked for more than 120 seconds.
>    "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
>    rmmod         D 0000000000000000     0  1608   1440 0x00000000
>      ffff880014245c78 0000000000000082 0000000000015bc0 0000000000015bc0
>      ffff880014804890 ffff880014245fd8 0000000000015bc0 ffff8800148044d0
>      0000000000015bc0 ffff880014245fd8 0000000000015bc0 ffff880014804890
>     Call Trace:
>     [<ffffffff81541b6d>] schedule_timeout+0x22d/0x300
>     [<ffffffff812b8716>] ? rb_erase+0xd6/0x160
>     [<ffffffff81052a10>] ? __dequeue_entity+0x30/0x50
>     [<ffffffff8154178b>] wait_for_common+0xdb/0x180
>     [<ffffffff8105a220>] ? default_wake_function+0x0/0x20
>     [<ffffffff815418ed>] wait_for_completion+0x1d/0x20
>     [<ffffffff8107fe55>] flush_cpu_workqueue+0x65/0xa0
>     [<ffffffff8107ff10>] ? wq_barrier_func+0x0/0x20
>     [<ffffffff81080754>] flush_workqueue+0x54/0x80
>     [<ffffffff810b5b24>] __stop_machine+0xf4/0x120
>     [<ffffffff8109d8c0>] ? __try_stop_module+0x0/0x50
>     [<ffffffff810b5d7e>] stop_machine+0x3e/0x60
>     [<ffffffff8109cbd4>] ? find_module+0x34/0x70
>     [<ffffffff8109e1ee>] sys_delete_module+0x17e/0x270
>     [<ffffffff810121b2>] system_call_fastpath+0x16/0x1b
> 
>   The process is waiting on kstop/0 to wake up and service the stop_cpu
>   workqueue work item that it has queued. kstop/0 is marked as
>   TASK_RUNNABLE, but doesn't appear to ever be getting scheduled:
> 
>       $ ps -f 1609
>       UID        PID  PPID  C STIME TTY      STAT   TIME CMD
>       root      1609     2  0 14:47 ?        R      0:00 [kstop/0]
> 
>       $ cat /proc/1609/stack
>       [<ffffffff8107fb6a>] worker_thread+0xda/0x110
>       [<ffffffff81084206>] kthread+0x96/0xa0
>       [<ffffffff810131ea>] child_rip+0xa/0x20
>       [<ffffffffffffffff>] 0xffffffffffffffff
> 
>   I tracked this behavior down and reported it to the upstream kernel,
>   but they say it's not a bug and that it's libcgroup's fault for moving
>   kthreadd into a cgroup without RT privs:
>   https://lkml.org/lkml/2011/1/5/53
> 
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Title:
  cgroup-bin should not move kthreadd into a default cgroup

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