1. 18 Apr, 2008 1 commit
    • Li Zefan's avatar
      cgroup: fix a race condition in manipulating tsk->cg_list · 0e04388f
      Li Zefan authored
      When I ran a test program to fork mass processes and at the same time
      'cat /cgroup/tasks', I got the following oops:
      
        ------------[ cut here ]------------
        kernel BUG at lib/list_debug.c:72!
        invalid opcode: 0000 [#1] SMP
        Pid: 4178, comm: a.out Not tainted (2.6.25-rc9 #72)
        ...
        Call Trace:
         [<c044a5f9>] ? cgroup_exit+0x55/0x94
         [<c0427acf>] ? do_exit+0x217/0x5ba
         [<c0427ed7>] ? do_group_exit+0.65/0x7c
         [<c0427efd>] ? sys_exit_group+0xf/0x11
         [<c0404842>] ? syscall_call+0x7/0xb
         [<c05e0000>] ? init_cyrix+0x2fa/0x479
        ...
        EIP: [<c04df671>] list_del+0x35/0x53 SS:ESP 0068:ebc7df4
        ---[ end trace caffb7332252612b ]---
        Fixing recursive fault but reboot is needed!
      
      After digging into the code and debugging, I finlly found out a race
      situation:
      
      				do_exit()
      				  ->cgroup_exit()
      				    ->if (!list_empty(&tsk->cg_list))
      				        list_del(&tsk->cg_list);
      
        cgroup_iter_start()
          ->cgroup_enable_task_cg_list()
            ->list_add(&tsk->cg_list, ..);
      
      In this case the list won't be deleted though the process has exited.
      
      We got two bug reports in the past, which seem to be the same bug as
      this one:
      	http://lkml.org/lkml/2008/3/5/332
      	http://lkml.org/lkml/2007/10/17/224
      
      Actually sometimes I got oops on list_del, sometimes oops on list_add.
      And I can change my test program a bit to trigger other oops.
      
      The patch has been tested both on x86_32 and x86_64.
      Signed-off-by: default avatarLi Zefan <lizf@cn.fujitsu.com>
      Acked-by: default avatarPaul Menage <menage@google.com>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: stable@kernel.org
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      0e04388f
  2. 17 Apr, 2008 2 commits
  3. 16 Apr, 2008 36 commits
  4. 15 Apr, 2008 1 commit