[patch] wait4-fix-2.5.34-A0, BK-curr

[Ingo Molnar]

the attached patch (against BK-curr) fixes a sys_wait4() bug noticed by
Ulrich Drepper. The kernel would not block properly if there are eligible
children delayed due to the new delayed thread-group-leader logic. The
solution is to introduce a new type of 'eligible child' type - and skip
over delayed children but set the wait4 flag nevertheless.

The libpthreads testcase that failed due to it now it works fine.

	Ingo

--- linux/kernel/exit.c.orig	Sun Sep 15 09:29:51 2002
+++ linux/kernel/exit.c	Sun Sep 15 09:26:42 2002
@@ -731,7 +731,7 @@
 	 * in a non-empty thread group:
 	 */
 	if (current->tgid != p->tgid && delay_group_leader(p))
-		return 0;
+		return 2;
 
 	if (security_ops->task_wait(p))
 		return 0;
@@ -757,11 +757,21 @@
 	do {
 		struct task_struct *p;
 		struct list_head *_p;
+		int ret;
+
 		list_for_each(_p,&tsk->children) {
 			p = list_entry(_p,struct task_struct,sibling);
-			if (!eligible_child(pid, options, p))
+
+			ret = eligible_child(pid, options, p);
+			if (!ret)
 				continue;
 			flag = 1;
+			/*
+			 * Eligible but we cannot release it yet:
+			 */
+			if (ret == 2)
+				continue;
+
 			switch (p->state) {
 			case TASK_STOPPED:
 				if (!p->exit_code)