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>

diff --git a/kernel/exit.c b/kernel/exit.c
index 190a4cdcdb4dde1b2c93a5386ed44d70122b677a..9ee229ea97e4dcb3c76716124601a9c3280974f1 100644 (file)
--- 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.