timer: add on-stack deferrable timer interfaces

In some cases (for instance with kernel threads) it may be desireable to
use on-stack deferrable timers to get their power saving benefits.  Add
interfaces to support this for the IPS driver.
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Matthew Garrett <mjg@redhat.com>

include/linux/timer.h

@@ -100,6 +100,13 @@ void init_timer_deferrable_key(struct timer_list *timer,
 		setup_timer_on_stack_key((timer), #timer, &__key,	\
 					 (fn), (data));			\
 	} while (0)
+#define setup_deferrable_timer_on_stack(timer, fn, data)		\
+	do {								\
+		static struct lock_class_key __key;			\
+		setup_deferrable_timer_on_stack_key((timer), #timer,	\
+						    &__key, (fn),	\
+						    (data));		\
+	} while (0)
 #else
 #define init_timer(timer)\
 	init_timer_key((timer), NULL, NULL)
@@ -111,6 +118,8 @@ void init_timer_deferrable_key(struct timer_list *timer,
 	setup_timer_key((timer), NULL, NULL, (fn), (data))
 #define setup_timer_on_stack(timer, fn, data)\
 	setup_timer_on_stack_key((timer), NULL, NULL, (fn), (data))
+#define setup_deferrable_timer_on_stack(timer, fn, data)\
+	setup_deferrable_timer_on_stack_key((timer), NULL, NULL, (fn), (data))
 #endif
 
 #ifdef CONFIG_DEBUG_OBJECTS_TIMERS
@@ -150,6 +159,12 @@ static inline void setup_timer_on_stack_key(struct timer_list *timer,
 	init_timer_on_stack_key(timer, name, key);
 }
 
+extern void setup_deferrable_timer_on_stack_key(struct timer_list *timer,
+						const char *name,
+						struct lock_class_key *key,
+						void (*function)(unsigned long),
+						unsigned long data);
+
 /**
  * timer_pending - is a timer pending?
  * @timer: the timer in question

kernel/timer.c

@@ -577,6 +577,19 @@ static void __init_timer(struct timer_list *timer,
 	lockdep_init_map(&timer->lockdep_map, name, key, 0);
 }
 
+void setup_deferrable_timer_on_stack_key(struct timer_list *timer,
+					 const char *name,
+					 struct lock_class_key *key,
+					 void (*function)(unsigned long),
+					 unsigned long data)
+{
+	timer->function = function;
+	timer->data = data;
+	init_timer_on_stack_key(timer, name, key);
+	timer_set_deferrable(timer);
+}
+EXPORT_SYMBOL_GPL(setup_deferrable_timer_on_stack_key);
+
 /**
  * init_timer_key - initialize a timer
  * @timer: the timer to be initialized