reparent_thread: don't call kill_orphaned_pgrp() if task_detached()
Oleg Nesterov [Thu, 2 Apr 2009 23:58:15 +0000 (16:58 -0700)]
If task_detached(p) == T, then either

  a) p is not the main thread, we will find the group leader on the
     ->children list.

or

  b) p is the group leader but its ->exit_state = EXIT_DEAD.  This
     can only happen when the last sub-thread has died, but in that case
     that thread has already called kill_orphaned_pgrp() from
     exit_notify().

In both cases kill_orphaned_pgrp() looks bogus.

Move the task_detached() check up and simplify the code, this is also
right from the "common sense" pov: we should do nothing with the detached
childs, except move them to the new parent's ->children list.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/exit.c

index 576eae2..405e687 100644 (file)
@@ -818,6 +818,8 @@ static void reparent_thread(struct task_struct *p, struct task_struct *father)
 
        list_move_tail(&p->sibling, &p->real_parent->children);
 
+       if (task_detached(p))
+               return;
        /* If this is a threaded reparent there is no need to
         * notify anyone anything has happened.
         */
@@ -825,15 +827,13 @@ static void reparent_thread(struct task_struct *p, struct task_struct *father)
                return;
 
        /* We don't want people slaying init.  */
-       if (!task_detached(p))
-               p->exit_signal = SIGCHLD;
+       p->exit_signal = SIGCHLD;
 
        /* If we'd notified the old parent about this child's death,
         * also notify the new parent.
         */
        if (!ptrace_reparented(p) &&
-           p->exit_state == EXIT_ZOMBIE &&
-           !task_detached(p) && thread_group_empty(p))
+           p->exit_state == EXIT_ZOMBIE && thread_group_empty(p))
                do_notify_parent(p, p->exit_signal);
 
        kill_orphaned_pgrp(p, father);