[RFC][PATCH -mm 3/3] freezer: Fix problem with kthread_stop

Rafael J. Wysocki
2007-04-22T20:01:38Z

From: Rafael J. Wysocki <rjw@sisk.pl>

Fix the problem with kthread_stop() that causes the freezer to fail if a
freezable thread is attempting to stop a frozen one and that may cause the
freezer to fail if the thread being stopped is freezable and
try_to_freeze_tasks() is running concurrently with kthread_stop().

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
---
kernel/kthread.c | 9 +++++++++
1 file changed, 9 insertions(+)

Index: linux-2.6.21-rc6-mm1/kernel/kthread.c
===================================================================
--- linux-2.6.21-rc6-mm1.orig/kernel/kthread.c 2007-04-09 15:23:48.000000000 +0200
+++ linux-2.6.21-rc6-mm1/kernel/kthread.c 2007-04-22 19:05:29.000000000 +0200
@@ -13,6 +13,7 @@
#include <linux/file.h>
#include <linux/module.h>
#include <linux/mutex.h>
+#include <linux/freezer.h>
#include <asm/semaphore.h>

/*
@@ -232,6 +233,14 @@ int kthread_stop(struct task_struct *k)

/* Now set kthread_should_stop() to true, and wake it up. */
kthread_stop_info.k = k;
+ if (!freezer_should_exempt(current)) {
+ /* We are freezable, so we must make sure that the thread being
+ * stopped is not frozen and will not be frozen until it dies
+ */
+ freezer_exempt(k);
+ if (frozen(k))
+ clear_frozen_flag(k);
+ }
wake_up_process(k);
put_task_struct(k);