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    Subject[PATCH 4/4] forget_original_parent: cleanup ptrace pathes
    No functional changes.

    - Fold ptrace_exit() into forget_original_parent(), it is trivial
    now. More importantly, this makes the code more symmetrical with
    reparent_thread().

    - The same for ptrace_exit_finish(), and "ptrace_" is not correct
    any longer.

    - "ptrace_dead" doesn't match the reality, rename to "dead_list".

    - swap the reparent_thread()'s arguments, just to make it more
    symmetrical with __ptrace_detach().

    Signed-off-by: Oleg Nesterov <oleg@redhat.com>

    --- 6.29-rc3/kernel/exit.c~8_CLEANUP 2009-01-29 08:03:18.000000000 +0100
    +++ 6.29-rc3/kernel/exit.c 2009-01-29 08:54:14.000000000 +0100
    @@ -770,42 +770,8 @@ int __ptrace_detach(struct task_struct *
    return 1;
    }

    -/*
    - * Detach all tasks we were using ptrace on.
    - * Any that need to be release_task'd are put on the @dead list.
    - *
    - * Called with write_lock(&tasklist_lock) held.
    - */
    -static void ptrace_exit(struct task_struct *parent, struct list_head *dead)
    -{
    - struct task_struct *p, *n;
    -
    - list_for_each_entry_safe(p, n, &parent->ptraced, ptrace_entry) {
    - if (__ptrace_detach(parent, p))
    - list_add(&p->ptrace_entry, dead);
    - }
    -}
    -
    -/*
    - * Finish up exit-time ptrace cleanup.
    - *
    - * Called without locks.
    - */
    -static void ptrace_exit_finish(struct task_struct *parent,
    - struct list_head *dead)
    -{
    - struct task_struct *p, *n;
    -
    - BUG_ON(!list_empty(&parent->ptraced));
    -
    - list_for_each_entry_safe(p, n, dead, ptrace_entry) {
    - list_del_init(&p->ptrace_entry);
    - release_task(p);
    - }
    -}
    -
    /* Returns nonzero if the child should be released. */
    -static int reparent_thread(struct task_struct *p, struct task_struct *father)
    +static int reparent_thread(struct task_struct *father, struct task_struct *p)
    {
    int dead;

    @@ -886,14 +852,17 @@ static struct task_struct *find_new_reap
    static void forget_original_parent(struct task_struct *father)
    {
    struct task_struct *p, *n, *reaper;
    - LIST_HEAD(ptrace_dead);
    + LIST_HEAD(dead_list);

    write_lock_irq(&tasklist_lock);
    reaper = find_new_reaper(father);
    /*
    * First clean up ptrace if we were using it.
    */
    - ptrace_exit(father, &ptrace_dead);
    + list_for_each_entry_safe(p, n, &father->ptraced, ptrace_entry) {
    + if (__ptrace_detach(father, p))
    + list_add(&p->ptrace_entry, &dead_list);
    + }

    list_for_each_entry_safe(p, n, &father->children, sibling) {
    p->real_parent = reaper;
    @@ -901,14 +870,18 @@ static void forget_original_parent(struc
    BUG_ON(p->ptrace);
    p->parent = p->real_parent;
    }
    - if (reparent_thread(p, father))
    - list_add(&p->ptrace_entry, &ptrace_dead);;
    + if (reparent_thread(father, p))
    + list_add(&p->ptrace_entry, &dead_list);;
    }
    -
    write_unlock_irq(&tasklist_lock);
    +
    BUG_ON(!list_empty(&father->children));
    + BUG_ON(!list_empty(&father->ptraced));

    - ptrace_exit_finish(father, &ptrace_dead);
    + list_for_each_entry_safe(p, n, &dead_list, ptrace_entry) {
    + list_del_init(&p->ptrace_entry);
    + release_task(p);
    + }
    }

    /*


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