do_wait: cleanup delay_group_leader() usage

eligible_child() == 2 means delay_group_leader().  With the previous patch
this only matters for EXIT_ZOMBIE task, we can move that special check to
the only place it is really needed.

Also, with this patch we don't skip security_task_wait() for the group
leaders in a non-empty thread group.  I don't really understand the exact
semantics of security_task_wait(), but imho this change is a bugfix.

Also rearrange the code a bit to kill an ugly "check_continued" backdoor.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Eric Paris <eparis@redhat.com>
Cc: James Morris <jmorris@namei.org>
Cc: Roland McGrath <roland@redhat.com>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 13 deletions

diff --git a/kernel/exit.c b/kernel/exit.c
index 190a4cdcdb4d..9ee229ea97e4 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -1140,12 +1140,6 @@ static int eligible_child(pid_t pid, int options, struct task_struct *p)
         if (((p->exit_signal != SIGCHLD) ^ ((options & __WCLONE) != 0))
             && !(options & __WALL))
                 return 0;
-        /*
-         * Do not consider thread group leaders that are
-         * in a non-empty thread group:
-         */
-        if (delay_group_leader(p))
-                return 2;
 
         err = security_task_wait(p);
         if (err)
@@ -1497,10 +1491,9 @@ repeat:
         tsk = current;
         do {
                 struct task_struct *p;
-                int ret;
 
                 list_for_each_entry(p, &tsk->children, sibling) {
-                        ret = eligible_child(pid, options, p);
+                        int ret = eligible_child(pid, options, p);
                         if (!ret)
                                 continue;
 
@@ -1524,19 +1517,17 @@ repeat:
                                 retval = wait_task_stopped(p,
                                                 (options & WNOWAIT), infop,
                                                 stat_addr, ru);
-                        } else if (p->exit_state == EXIT_ZOMBIE) {
+                        } else if (p->exit_state == EXIT_ZOMBIE &&
+                                        !delay_group_leader(p)) {
                                 /*
-                                 * Eligible but we cannot release it yet:
+                                 * We don't reap group leaders with subthreads.
                                  */
-                                if (ret == 2)
-                                        goto check_continued;
                                 if (!likely(options & WEXITED))
                                         continue;
                                 retval = wait_task_zombie(p,
                                                 (options & WNOWAIT), infop,
                                                 stat_addr, ru);
                         } else if (p->exit_state != EXIT_DEAD) {
-check_continued:
                                 /*
                                  * It's running now, so it might later
                                  * exit, stop, or stop and then continue.