From: Ingo Molnar <mingo@elte.hu>

disable preemption in the self-reap codepath, as such tasks may not be on
the tasklist anymore and CPU-hotplug relies on the tasklist to migrate
tasks.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---

 25-akpm/kernel/exit.c |    7 +++++++
 1 files changed, 7 insertions(+)

diff -puN kernel/exit.c~sched-self-reap-fix kernel/exit.c
--- 25/kernel/exit.c~sched-self-reap-fix	2004-08-20 02:04:27.375584976 -0700
+++ 25-akpm/kernel/exit.c	2004-08-20 02:04:27.382583912 -0700
@@ -24,6 +24,7 @@
 #include <linux/proc_fs.h>
 #include <linux/mempolicy.h>
 #include <linux/perfctr.h>
+#include <linux/cpu.h>
 
 #include <asm/uaccess.h>
 #include <asm/unistd.h>
@@ -783,8 +784,14 @@ static void exit_notify(struct task_stru
 
 	/* If the process is dead, release it - nobody will wait for it */
 	if (state == TASK_DEAD) {
+		lock_cpu_hotplug();
 		release_task(tsk);
 		write_lock_irq(&tasklist_lock);
+		/*
+		 * No preemption may happen from this point on,
+		 * or CPU hotplug (and task exit) breaks:
+		 */
+		unlock_cpu_hotplug();
 		tsk->state = state;
 		_raw_write_unlock(&tasklist_lock);
 		local_irq_enable();
_