[PATCH] rtc_cmos oops fix
Fix an oops on the rtc_device_unregister() path by waiting until the last
moment before nulling the rtc->ops vector. Fix some potential oopses by
having the rtc_class_open()/rtc_class_close() interface increase the RTC's
reference count while an RTC handle is available outside the RTC framework.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/rtc/class.c b/drivers/rtc/class.c
index 7a0d8ee..04aaa63 100644
--- a/drivers/rtc/class.c
+++ b/drivers/rtc/class.c
@@ -113,10 +113,16 @@
*/
void rtc_device_unregister(struct rtc_device *rtc)
{
- mutex_lock(&rtc->ops_lock);
- rtc->ops = NULL;
- mutex_unlock(&rtc->ops_lock);
- class_device_unregister(&rtc->class_dev);
+ if (class_device_get(&rtc->class_dev) != NULL) {
+ mutex_lock(&rtc->ops_lock);
+ /* remove innards of this RTC, then disable it, before
+ * letting any rtc_class_open() users access it again
+ */
+ class_device_unregister(&rtc->class_dev);
+ rtc->ops = NULL;
+ mutex_unlock(&rtc->ops_lock);
+ class_device_put(&rtc->class_dev);
+ }
}
EXPORT_SYMBOL_GPL(rtc_device_unregister);
diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c
index 6f11f6d..ef40df0 100644
--- a/drivers/rtc/interface.c
+++ b/drivers/rtc/interface.c
@@ -179,7 +179,7 @@
down(&rtc_class->sem);
list_for_each_entry(class_dev_tmp, &rtc_class->children, node) {
if (strncmp(class_dev_tmp->class_id, name, BUS_ID_SIZE) == 0) {
- class_dev = class_dev_tmp;
+ class_dev = class_device_get(class_dev_tmp);
break;
}
}
@@ -197,6 +197,7 @@
void rtc_class_close(struct class_device *class_dev)
{
module_put(to_rtc_device(class_dev)->owner);
+ class_device_put(class_dev);
}
EXPORT_SYMBOL_GPL(rtc_class_close);