On Tue, Feb 11, 2014 at 04:05:46PM +0800, Li Zefan wrote:
> Setup cgroupfs like this:
> # mount -t cgroup -o cpuacct xxx /cgroup
> # mkdir /cgroup/sub1
> # mkdir /cgroup/sub2
>
> Then run these two commands:
> # for ((; ;)) { mkdir /cgroup/sub1/tmp && rmdir /mnt/sub1/tmp; } &
> # for ((; ;)) { mkdir /cgroup/sub2/tmp && rmdir /mnt/sub2/tmp; } &
>
> After seconds you may see this warning:
>
> ------------[ cut here ]------------
> WARNING: CPU: 1 PID: 25243 at lib/idr.c:527 sub_remove+0x87/0x1b0()
> idr_remove called for id=6 which is not allocated.
> ...
> Call Trace:
> [<ffffffff8156063c>] dump_stack+0x7a/0x96
> [<ffffffff810591ac>] warn_slowpath_common+0x8c/0xc0
> [<ffffffff81059296>] warn_slowpath_fmt+0x46/0x50
> [<ffffffff81300aa7>] sub_remove+0x87/0x1b0
> [<ffffffff810f3f02>] ? css_killed_work_fn+0x32/0x1b0
> [<ffffffff81300bf5>] idr_remove+0x25/0xd0
> [<ffffffff810f2bab>] cgroup_destroy_css_killed+0x5b/0xc0
> [<ffffffff810f4000>] css_killed_work_fn+0x130/0x1b0
> [<ffffffff8107cdbc>] process_one_work+0x26c/0x550
> [<ffffffff8107eefe>] worker_thread+0x12e/0x3b0
> [<ffffffff81085f96>] kthread+0xe6/0xf0
> [<ffffffff81570bac>] ret_from_fork+0x7c/0xb0
> ---[ end trace 2d1577ec10cf80d0 ]---
>
> It's because allocating/removing cgroup ID is not properly synchronized.
>
> The bug was introduced when we converted cgroup_ida to cgroup_idr.
> While synchronization is already done inside ida_simple_{get,remove}(),
> users are responsible for concurrent calls to idr_{alloc,remove}().
>
> Fixes: 4e96ee8e981b ("cgroup: convert cgroup_ida to cgroup_idr")
> Cc: <stable@xxxxxxxxxxxxxxx> #3.12+
> Reported-by: Michal Hocko <mhocko@xxxxxxx>
> Signed-off-by: Li Zefan <lizefan@xxxxxxxxxx>
Jesus, you're right. I missed that completely. It conflicts with the
return value fix in cgroup/for-3.14-fixes but easy to fix up.
Applying to cgroup/for-3.14-fixes.
Thanks!
--
tejun
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