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Subject[PATCH 4/8] 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>
---

include/linux/sched.h | 2 +-
kernel/exit.c | 29 ++++++++---------------------
2 files changed, 9 insertions(+), 22 deletions(-)

--- ptrace/include/linux/sched.h~4_all_notify_callers 2011-06-22 22:47:11.000000000 +0200
+++ ptrace/include/linux/sched.h 2011-06-22 22:47:12.000000000 +0200
@@ -2161,7 +2161,7 @@ extern int kill_pid_info_as_uid(int, str
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);
--- ptrace/kernel/exit.c~4_all_notify_callers 2011-06-22 22:47:11.000000000 +0200
+++ ptrace/kernel/exit.c 2011-06-22 22:47:12.000000000 +0200
@@ -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;
}
@@ -765,8 +756,7 @@ static void reparent_leader(struct task_
/* 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);
}
@@ -1348,16 +1338,13 @@ static int wait_task_zombie(struct wait_
/* 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);
}


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