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Subject[PATCH 5/7] Freezer: Fix kthread_create vs freezer theoretical race
Date
From: Oleg Nesterov <oleg@tv-sign.ru>

kthread() sleeps in TASK_INTERRUPTIBLE state waiting for the first wakeup. In
theory, this wakeup may come from freeze_process()->signal_wake_up(), so the
task can disappear even before kthread_create() sets its ->comm.

Change kthread() to use TASK_UNINTERRUPTIBLE.

[akpm@linux-foundation.org: s/BUG_ON/WARN_ON+recover]

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
---
kernel/kthread.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
Index: linux-2.6/kernel/kthread.c
===================================================================
--- linux-2.6.orig/kernel/kthread.c 2007-05-10 21:44:23.000000000 +0200
+++ linux-2.6/kernel/kthread.c 2007-05-10 21:44:43.000000000 +0200
@@ -70,7 +70,7 @@ static int kthread(void *_create)
data = create->data;

/* OK, tell user we're spawned, wait for stop or wakeup */
- __set_current_state(TASK_INTERRUPTIBLE);
+ __set_current_state(TASK_UNINTERRUPTIBLE);
complete(&create->started);
schedule();

@@ -162,7 +162,10 @@ EXPORT_SYMBOL(kthread_create);
*/
void kthread_bind(struct task_struct *k, unsigned int cpu)
{
- BUG_ON(k->state != TASK_INTERRUPTIBLE);
+ if (k->state != TASK_UNINTERRUPTIBLE) {
+ WARN_ON(1);
+ return;
+ }
/* Must have done schedule() in kthread() before we set_task_cpu */
wait_task_inactive(k);
set_task_cpu(k, cpu);
-
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