[PATCH] CPU hotplug breaks wake_up_new_task

Fix a problem wherein a new-born task is added to a dead CPU.
Signed-off-by: NSrivatsa Vaddagiri <vatsa@in.ibm.com>
Acked-by: NNick Piggin <nickpiggin@yahoo.com.au>
Acked-by: NShaohua Li <shaohua.li@intel.com>
Acked-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

kernel/fork.c

@@ -1062,7 +1062,8 @@ static task_t *copy_process(unsigned long clone_flags,
 	 * parent's CPU). This avoids alot of nasty races.
 	 */
 	p->cpus_allowed = current->cpus_allowed;
-	if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed)))
+	if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) ||
+			!cpu_online(task_cpu(p))))
 		set_task_cpu(p, smp_processor_id());
 
 	/*