1. 11 2月, 2014 1 次提交
    • L
      cgroup: protect modifications to cgroup_idr with cgroup_mutex · 0ab02ca8
      Li Zefan 提交于
      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}().
      
      tj: Refreshed on top of b58c8998 ("cgroup: fix error return from
      cgroup_create()").
      
      Fixes: 4e96ee8e ("cgroup: convert cgroup_ida to cgroup_idr")
      Cc: <stable@vger.kernel.org> #3.12+
      Reported-by: NMichal Hocko <mhocko@suse.cz>
      Signed-off-by: NLi Zefan <lizefan@huawei.com>
      Signed-off-by: NTejun Heo <tj@kernel.org>
      0ab02ca8
  2. 01 2月, 2014 1 次提交
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