freezer: fix kthread_create vs freezer theoretical race
authorOleg Nesterov <oleg@tv-sign.ru>
Wed, 23 May 2007 20:57:27 +0000 (13:57 -0700)
committerLinus Torvalds <torvalds@woody.linux-foundation.org>
Thu, 24 May 2007 03:14:11 +0000 (20:14 -0700)
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>
Cc: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
kernel/kthread.c

index df8a8e8f6ca4fbb55d2da6770f9040d31de9cf0b..bbd51b81a3e86e239584925dfaf637dce187a831 100644 (file)
@@ -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);