debugobjects: add timer specific object debugging code

Add calls to the generic object debugging infrastructure and provide fixup
functions which allow to keep the system alive when recoverable problems have
been detected by the object debugging core code.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Greg KH <greg@kroah.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/parport/ieee1284.c

@@ -76,7 +76,7 @@ int parport_wait_event (struct parport *port, signed long timeout)
 		   semaphore. */
 		return 1;
 
-	init_timer (&timer);
+	init_timer_on_stack(&timer);
 	timer.expires = jiffies + timeout;
 	timer.function = timeout_waiting_on_port;
 	port_from_cookie[port->number % PARPORT_MAX] = port;
@@ -88,6 +88,8 @@ int parport_wait_event (struct parport *port, signed long timeout)
 		/* Timed out. */
 		ret = 1;
 
+	destroy_timer_on_stack(&timer);
+
 	return ret;
 }
 

fs/aio.c

@@ -1078,9 +1078,7 @@ static void timeout_func(unsigned long data)
 
 static inline void init_timeout(struct aio_timeout *to)
 {
-	init_timer(&to->timer);
-	to->timer.data = (unsigned long)to;
-	to->timer.function = timeout_func;
+	setup_timer_on_stack(&to->timer, timeout_func, (unsigned long) to);
 	to->timed_out = 0;
 	to->p = current;
 }
@@ -1213,6 +1211,7 @@ retry:
 	if (timeout)
 		clear_timeout(&to);
 out:
+	destroy_timer_on_stack(&to.timer);
 	return i ? i : ret;
 }
 

include/linux/poison.h

@@ -10,6 +10,13 @@
 #define LIST_POISON1  ((void *) 0x00100100)
 #define LIST_POISON2  ((void *) 0x00200200)
 
+/********** include/linux/timer.h **********/
+/*
+ * Magic number "tsta" to indicate a static timer initializer
+ * for the object debugging code.
+ */
+#define TIMER_ENTRY_STATIC	((void *) 0x74737461)
+
 /********** mm/slab.c **********/
 /*
  * Magic nums for obj red zoning.

include/linux/timer.h

@@ -4,6 +4,7 @@
 #include <linux/list.h>
 #include <linux/ktime.h>
 #include <linux/stddef.h>
+#include <linux/debugobjects.h>
 
 struct tvec_base;
 
@@ -25,6 +26,7 @@ struct timer_list {
 extern struct tvec_base boot_tvec_bases;
 
 #define TIMER_INITIALIZER(_function, _expires, _data) {		\
+		.entry = { .prev = TIMER_ENTRY_STATIC },	\
 		.function = (_function),			\
 		.expires = (_expires),				\
 		.data = (_data),				\
@@ -38,6 +40,17 @@ extern struct tvec_base boot_tvec_bases;
 void init_timer(struct timer_list *timer);
 void init_timer_deferrable(struct timer_list *timer);
 
+#ifdef CONFIG_DEBUG_OBJECTS_TIMERS
+extern void init_timer_on_stack(struct timer_list *timer);
+extern void destroy_timer_on_stack(struct timer_list *timer);
+#else
+static inline void destroy_timer_on_stack(struct timer_list *timer) { }
+static inline void init_timer_on_stack(struct timer_list *timer)
+{
+	init_timer(timer);
+}
+#endif
+
 static inline void setup_timer(struct timer_list * timer,
 				void (*function)(unsigned long),
 				unsigned long data)
@@ -47,6 +60,15 @@ static inline void setup_timer(struct timer_list * timer,
 	init_timer(timer);
 }
 
+static inline void setup_timer_on_stack(struct timer_list *timer,
+					void (*function)(unsigned long),
+					unsigned long data)
+{
+	timer->function = function;
+	timer->data = data;
+	init_timer_on_stack(timer);
+}
+
 /**
  * timer_pending - is a timer pending?
  * @timer: the timer in question
@@ -164,5 +186,4 @@ unsigned long __round_jiffies_relative(unsigned long j, int cpu);
 unsigned long round_jiffies(unsigned long j);
 unsigned long round_jiffies_relative(unsigned long j);
 
-
 #endif

kernel/timer.c

@@ -320,14 +320,130 @@ static void timer_stats_account_timer(struct timer_list *timer)
 static void timer_stats_account_timer(struct timer_list *timer) {}
 #endif
 
-/**
- * init_timer - initialize a timer.
- * @timer: the timer to be initialized
- *
- * init_timer() must be done to a timer prior calling *any* of the
- * other timer functions.
+#ifdef CONFIG_DEBUG_OBJECTS_TIMERS
+
+static struct debug_obj_descr timer_debug_descr;
+
+/*
+ * fixup_init is called when:
+ * - an active object is initialized
  */
-void init_timer(struct timer_list *timer)
+static int timer_fixup_init(void *addr, enum debug_obj_state state)
+{
+	struct timer_list *timer = addr;
+
+	switch (state) {
+	case ODEBUG_STATE_ACTIVE:
+		del_timer_sync(timer);
+		debug_object_init(timer, &timer_debug_descr);
+		return 1;
+	default:
+		return 0;
+	}
+}
+
+/*
+ * fixup_activate is called when:
+ * - an active object is activated
+ * - an unknown object is activated (might be a statically initialized object)
+ */
+static int timer_fixup_activate(void *addr, enum debug_obj_state state)
+{
+	struct timer_list *timer = addr;
+
+	switch (state) {
+
+	case ODEBUG_STATE_NOTAVAILABLE:
+		/*
+		 * This is not really a fixup. The timer was
+		 * statically initialized. We just make sure that it
+		 * is tracked in the object tracker.
+		 */
+		if (timer->entry.next == NULL &&
+		    timer->entry.prev == TIMER_ENTRY_STATIC) {
+			debug_object_init(timer, &timer_debug_descr);
+			debug_object_activate(timer, &timer_debug_descr);
+			return 0;
+		} else {
+			WARN_ON_ONCE(1);
+		}
+		return 0;
+
+	case ODEBUG_STATE_ACTIVE:
+		WARN_ON(1);
+
+	default:
+		return 0;
+	}
+}
+
+/*
+ * fixup_free is called when:
+ * - an active object is freed
+ */
+static int timer_fixup_free(void *addr, enum debug_obj_state state)
+{
+	struct timer_list *timer = addr;
+
+	switch (state) {
+	case ODEBUG_STATE_ACTIVE:
+		del_timer_sync(timer);
+		debug_object_free(timer, &timer_debug_descr);
+		return 1;
+	default:
+		return 0;
+	}
+}
+
+static struct debug_obj_descr timer_debug_descr = {
+	.name		= "timer_list",
+	.fixup_init	= timer_fixup_init,
+	.fixup_activate	= timer_fixup_activate,
+	.fixup_free	= timer_fixup_free,
+};
+
+static inline void debug_timer_init(struct timer_list *timer)
+{
+	debug_object_init(timer, &timer_debug_descr);
+}
+
+static inline void debug_timer_activate(struct timer_list *timer)
+{
+	debug_object_activate(timer, &timer_debug_descr);
+}
+
+static inline void debug_timer_deactivate(struct timer_list *timer)
+{
+	debug_object_deactivate(timer, &timer_debug_descr);
+}
+
+static inline void debug_timer_free(struct timer_list *timer)
+{
+	debug_object_free(timer, &timer_debug_descr);
+}
+
+static void __init_timer(struct timer_list *timer);
+
+void init_timer_on_stack(struct timer_list *timer)
+{
+	debug_object_init_on_stack(timer, &timer_debug_descr);
+	__init_timer(timer);
+}
+EXPORT_SYMBOL_GPL(init_timer_on_stack);
+
+void destroy_timer_on_stack(struct timer_list *timer)
+{
+	debug_object_free(timer, &timer_debug_descr);
+}
+EXPORT_SYMBOL_GPL(destroy_timer_on_stack);
+
+#else
+static inline void debug_timer_init(struct timer_list *timer) { }
+static inline void debug_timer_activate(struct timer_list *timer) { }
+static inline void debug_timer_deactivate(struct timer_list *timer) { }
+#endif
+
+static void __init_timer(struct timer_list *timer)
 {
 	timer->entry.next = NULL;
 	timer->base = __raw_get_cpu_var(tvec_bases);
@@ -337,6 +453,19 @@ void init_timer(struct timer_list *timer)
 	memset(timer->start_comm, 0, TASK_COMM_LEN);
 #endif
 }
+
+/**
+ * init_timer - initialize a timer.
+ * @timer: the timer to be initialized
+ *
+ * init_timer() must be done to a timer prior calling *any* of the
+ * other timer functions.
+ */
+void init_timer(struct timer_list *timer)
+{
+	debug_timer_init(timer);
+	__init_timer(timer);
+}
 EXPORT_SYMBOL(init_timer);
 
 void init_timer_deferrable(struct timer_list *timer)
@@ -351,6 +480,8 @@ static inline void detach_timer(struct timer_list *timer,
 {
 	struct list_head *entry = &timer->entry;
 
+	debug_timer_deactivate(timer);
+
 	__list_del(entry->prev, entry->next);
 	if (clear_pending)
 		entry->next = NULL;
@@ -405,6 +536,8 @@ int __mod_timer(struct timer_list *timer, unsigned long expires)
 		ret = 1;
 	}
 
+	debug_timer_activate(timer);
+
 	new_base = __get_cpu_var(tvec_bases);
 
 	if (base != new_base) {
@@ -450,6 +583,7 @@ void add_timer_on(struct timer_list *timer, int cpu)
 	BUG_ON(timer_pending(timer) || !timer->function);
 	spin_lock_irqsave(&base->lock, flags);
 	timer_set_base(timer, base);
+	debug_timer_activate(timer);
 	internal_add_timer(base, timer);
 	/*
 	 * Check whether the other CPU is idle and needs to be
@@ -1086,11 +1220,14 @@ signed long __sched schedule_timeout(signed long timeout)
 
 	expire = timeout + jiffies;
 
-	setup_timer(&timer, process_timeout, (unsigned long)current);
+	setup_timer_on_stack(&timer, process_timeout, (unsigned long)current);
 	__mod_timer(&timer, expire);
 	schedule();
 	del_singleshot_timer_sync(&timer);
 
+	/* Remove the timer from the object tracker */
+	destroy_timer_on_stack(&timer);
+
 	timeout = expire - jiffies;
 
  out:

lib/Kconfig.debug

@@ -217,6 +217,14 @@ config DEBUG_OBJECTS_FREE
 	  properly. This can make kmalloc/kfree-intensive workloads
 	  much slower.
 
+config DEBUG_OBJECTS_TIMERS
+	bool "Debug timer objects"
+	depends on DEBUG_OBJECTS
+	help
+	  If you say Y here, additional code will be inserted into the
+	  timer routines to track the life time of timer objects and
+	  validate the timer operations.
+
 config DEBUG_SLAB
 	bool "Debug slab memory allocations"
 	depends on DEBUG_KERNEL && SLAB