make do_notify_parent() __must_check, update the callers

Change other callers of do_notify_parent() to check the value it
returns, this makes the subsequent task_detached() unnecessary.
Mark do_notify_parent() as __must_check.

Use thread_group_leader() instead of !task_detached() to check
if we need to notify the real parent in wait_task_zombie().

Remove the stale comment in release_task(). "just for sanity" is
no longer true, we have to set EXIT_DEAD to avoid the races with
do_wait().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Tejun Heo <tj@kernel.org>

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 0df7231d9ee0044a0cb078e737800f4704dcfdb7..0cb4f097f76c30d382aff84dcf297e99b291b27f 100644 (file)
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2160,7 +2160,7 @@ extern int kill_pid_info_as_uid(int, struct siginfo *, struct pid *, uid_t, uid_
 extern int kill_pgrp(struct pid *pid, int sig, int priv);
 extern int kill_pid(struct pid *pid, int sig, int priv);
 extern int kill_proc_info(int, struct siginfo *, pid_t);
-extern bool do_notify_parent(struct task_struct *, int);
+extern __must_check bool do_notify_parent(struct task_struct *, int);
 extern void __wake_up_parent(struct task_struct *p, struct task_struct *parent);
 extern void force_sig(int, struct task_struct *);
 extern int send_sig(int, struct task_struct *, int);

diff --git a/kernel/exit.c b/kernel/exit.c
index bb08e938ca7490bd7bfe648ca5e4cd2481769f14..f68d137ffeb460566978aa3065dd07932062f0aa 100644 (file)
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -190,21 +190,12 @@ repeat:
        leader = p->group_leader;
        if (leader != p && thread_group_empty(leader) && leader->exit_state == EXIT_ZOMBIE) {
                BUG_ON(task_detached(leader));
-               do_notify_parent(leader, leader->exit_signal);
                /*
                 * If we were the last child thread and the leader has
                 * exited already, and the leader's parent ignores SIGCHLD,
                 * then we are the one who should release the leader.
-                *
-                * do_notify_parent() will have marked it self-reaping in
-                * that case.
-                */
-               zap_leader = task_detached(leader);
-
-               /*
-                * This maintains the invariant that release_task()
-                * only runs on a task in EXIT_DEAD, just for sanity.
                 */
+               zap_leader = do_notify_parent(leader, leader->exit_signal);
                if (zap_leader)
                        leader->exit_state = EXIT_DEAD;
        }
@@ -766,8 +757,7 @@ static void reparent_leader(struct task_struct *father, struct task_struct *p,
        /* If it has exited notify the new parent about this child's death. */
        if (!p->ptrace &&
            p->exit_state == EXIT_ZOMBIE && thread_group_empty(p)) {
-               do_notify_parent(p, p->exit_signal);
-               if (task_detached(p)) {
+               if (do_notify_parent(p, p->exit_signal)) {
                        p->exit_state = EXIT_DEAD;
                        list_move_tail(&p->sibling, dead);
                }
@@ -1351,16 +1341,13 @@ static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
                /* We dropped tasklist, ptracer could die and untrace */
                ptrace_unlink(p);
                /*
-                * If this is not a detached task, notify the parent.
-                * If it's still not detached after that, don't release
-                * it now.
+                * If this is not a sub-thread, notify the parent.
+                * If parent wants a zombie, don't release it now.
                 */
-               if (!task_detached(p)) {
-                       do_notify_parent(p, p->exit_signal);
-                       if (!task_detached(p)) {
-                               p->exit_state = EXIT_ZOMBIE;
-                               p = NULL;
-                       }
+               if (thread_group_leader(p) &&
+                   !do_notify_parent(p, p->exit_signal)) {
+                       p->exit_state = EXIT_ZOMBIE;
+                       p = NULL;
                }
                write_unlock_irq(&tasklist_lock);
        }