[PATCH] detached-fix-2.5.34-A0, BK-curr

This fixes three resource accounting related bugs introduced by detached
threads:

 - the 'child CPU usage' fields were updated in wait4 until now - this was
   slightly buggy for a number of reasons, eg. if the exit_code writout
   faults then it's possible to trigger this code multiple times.

 - those threads that do not go through wait4 were not properly accounted.

 - sched_exit() was incorrectly assuming that current == parent. In the
   detached case p->parent is the real parent.

with this patch applied things like 'time' work again for new-style
threaded apps.

kernel/exit.c

@@ -71,19 +71,19 @@ static void release_task(struct task_struct * p)
 	write_lock_irq(&tasklist_lock);
 	__exit_sighand(p);
 	proc_dentry = __unhash_process(p);
+	p->parent->cutime += p->utime + p->cutime;
+	p->parent->cstime += p->stime + p->cstime;
+	p->parent->cmin_flt += p->min_flt + p->cmin_flt;
+	p->parent->cmaj_flt += p->maj_flt + p->cmaj_flt;
+	p->parent->cnswap += p->nswap + p->cnswap;
+	sched_exit(p);
 	write_unlock_irq(&tasklist_lock);
+
 	if (unlikely(proc_dentry != NULL)) {
 		shrink_dcache_parent(proc_dentry);
 		dput(proc_dentry);
 	}
-
 	release_thread(p);
-	if (p != current) {
-		current->cmin_flt += p->min_flt + p->cmin_flt;
-		current->cmaj_flt += p->maj_flt + p->cmaj_flt;
-		current->cnswap += p->nswap + p->cnswap;
-		sched_exit(p);
-	}
 	put_task_struct(p);
 }
 
@@ -794,8 +794,6 @@ asmlinkage long sys_wait4(pid_t pid,unsigned int * stat_addr, int options, struc
 				}
 				goto end_wait4;
 			case TASK_ZOMBIE:
-				current->cutime += p->utime + p->cutime;
-				current->cstime += p->stime + p->cstime;
 				read_unlock(&tasklist_lock);
 				retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
 				if (!retval && stat_addr) {

kernel/sched.c

@@ -479,17 +479,17 @@ void sched_exit(task_t * p)
 {
 	local_irq_disable();
 	if (p->first_time_slice) {
-		current->time_slice += p->time_slice;
-		if (unlikely(current->time_slice > MAX_TIMESLICE))
-			current->time_slice = MAX_TIMESLICE;
+		p->parent->time_slice += p->time_slice;
+		if (unlikely(p->parent->time_slice > MAX_TIMESLICE))
+			p->parent->time_slice = MAX_TIMESLICE;
 	}
 	local_irq_enable();
 	/*
 	 * If the child was a (relative-) CPU hog then decrease
 	 * the sleep_avg of the parent as well.
 	 */
-	if (p->sleep_avg < current->sleep_avg)
-		current->sleep_avg = (current->sleep_avg * EXIT_WEIGHT +
+	if (p->sleep_avg < p->parent->sleep_avg)
+		p->parent->sleep_avg = (p->parent->sleep_avg * EXIT_WEIGHT +
 			p->sleep_avg) / (EXIT_WEIGHT + 1);
 }