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    SubjectRe: [RFC] fs, proc: Introduce /proc/<pid>/task/<tid>/children entry v6
    On Mon, Jan 16, 2012 at 05:11:14PM +0100, Oleg Nesterov wrote:
    > On 01/16, Cyrill Gorcunov wrote:
    > >
    > > +get_children_pid(struct proc_pid_children_iter *iter, struct pid *pid_prev, loff_t pos)
    > > +{
    > > + struct task_struct *start, *task;
    > > + struct pid *pid = NULL;
    > > +
    > > + read_lock(&tasklist_lock);
    > > +
    > > + start = pid_task(iter->pid_start, PIDTYPE_PID);
    > > + if (!start)
    > > + goto out;
    > > +
    > > + /*
    > > + * Lets try to continue searching first, this gives
    > > + * us significant speedup on children-rich processes.
    > > + */
    > > + if (pid_prev) {
    > > + task = pid_task(pid_prev, PIDTYPE_PID);
    > > + if (task && task->real_parent == start &&
    > > + !(list_empty(&task->sibling))) {
    >
    > Damn. No, this is wrong.
    >
    > Damn! Yes, it was we who told you to check list_empty(sibling) ;)
    >
    > But this is not enough. exit_ptrace() can do list_move() without
    > changing ->real_parent.
    >
    > I'll try to think. At first glance we can rely on EXIT_DEAD, but
    > I'd like to avoid this, I think EXIT_DEAD should die.
    >

    Ouch! Thanks for catching this Oleg. I'll try to come with something
    to show as well.

    Cyrill


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