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    SubjectRe: [PATCH] rework/fix is_single_threaded()
    On Mon, 13 Apr 2009 23:45:13 +0200
    Oleg Nesterov <> wrote:

    > - Fix the comment, is_single_threaded(p) actually means that nobody shares
    > ->mm with p.
    > I think this helper should be renamed, and it should not have arguments.
    > With or without this patch it must not be used unless p == current,
    > otherwise we can't safely use p->signal or p->mm.
    > - "if (atomic_read(&p->signal->count) != 1)" is not right when we have a
    > zombie group leader, use signal->live instead.
    > - Add PF_KTHREAD check to skip kernel threads which may borrow p->mm,
    > otherwise we can return the wrong "false".
    > - Use for_each_process() instead of do_each_thread(), all threads must use
    > the same ->mm.
    > - Use down_write(mm->mmap_sem) + rcu_read_lock() instead of tasklist_lock
    > to iterate over the process list. If there is another CLONE_VM process
    > it can't pass exit_mm() which takes the same mm->mmap_sem. We can miss
    > a freshly forked CLONE_VM task, but this doesn't matter because we must
    > see its parent and return false.

    hum. I'm searching for a reason to merge this into 2.6.30 but I'm not
    seeing one?

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      Last update: 2009-04-16 01:39    [W:0.020 / U:4.164 seconds]
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