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Message-Id: <1233241400.4035.6.camel@johannes.local>
Date: Thu, 29 Jan 2009 16:03:20 +0100
From: Johannes Berg <johannes@...solutions.net>
To: Ingo Molnar <mingo@...e.hu>
Cc: Peter Zijlstra <peterz@...radead.org>,
Thomas Gleixner <tglx@...utronix.de>,
Linux Kernel list <linux-kernel@...r.kernel.org>
Subject: [PATCH v4] timer: implement lockdep deadlock detection
This modifies the timer code in a way to allow lockdep to detect
deadlocks resulting from a lock being taken in the timer function
as well as around the del_timer_sync() call.
Signed-off-by: Johannes Berg <johannes@...solutions.net>
---
v2: fix coding/comment style
v3: accept freeing timer from timer function, fix init_timer_on_stack
in no-lockdep case
v4: fix statically declared timer names/lockdep keys
include/linux/timer.h | 93 +++++++++++++++++++++++++++++++++++++++++++++-----
kernel/timer.c | 70 +++++++++++++++++++++++++++++++------
2 files changed, 142 insertions(+), 21 deletions(-)
--- wireless-testing.orig/include/linux/timer.h 2009-01-28 11:33:17.000000000 +0100
+++ wireless-testing/include/linux/timer.h 2009-01-29 16:01:49.000000000 +0100
@@ -5,6 +5,7 @@
#include <linux/ktime.h>
#include <linux/stddef.h>
#include <linux/debugobjects.h>
+#include <linux/stringify.h>
struct tvec_base;
@@ -21,52 +22,126 @@ struct timer_list {
char start_comm[16];
int start_pid;
#endif
+#ifdef CONFIG_LOCKDEP
+ struct lockdep_map lockdep_map;
+#endif
};
extern struct tvec_base boot_tvec_bases;
+#ifdef CONFIG_LOCKDEP
+/*
+ * NB: because we have to copy the lockdep_map, setting the lockdep_map key
+ * (second argument) here is required, otherwise it could be initialised to
+ * the copy of the lockdep_map later! We use the pointer to and the string
+ * "<file>:<line>" as the key resp. the name of the lockdep_map.
+ */
+#define __TIMER_LOCKDEP_MAP_INITIALIZER(_kn) \
+ .lockdep_map = STATIC_LOCKDEP_MAP_INIT(_kn, &_kn),
+#else
+#define __TIMER_LOCKDEP_MAP_INITIALIZER(_kn)
+#endif
+
#define TIMER_INITIALIZER(_function, _expires, _data) { \
.entry = { .prev = TIMER_ENTRY_STATIC }, \
.function = (_function), \
.expires = (_expires), \
.data = (_data), \
.base = &boot_tvec_bases, \
+ __TIMER_LOCKDEP_MAP_INITIALIZER( \
+ __FILE__ ":" __stringify(__LINE__)) \
}
#define DEFINE_TIMER(_name, _function, _expires, _data) \
struct timer_list _name = \
TIMER_INITIALIZER(_function, _expires, _data)
-void init_timer(struct timer_list *timer);
-void init_timer_deferrable(struct timer_list *timer);
+void init_timer_key(struct timer_list *timer,
+ const char *name,
+ struct lock_class_key *key);
+void init_timer_deferrable_key(struct timer_list *timer,
+ const char *name,
+ struct lock_class_key *key);
+
+#ifdef CONFIG_LOCKDEP
+#define init_timer(timer) \
+ do { \
+ static struct lock_class_key __key; \
+ init_timer_key((timer), #timer, &__key); \
+ } while (0)
+
+#define init_timer_deferrable(timer) \
+ do { \
+ static struct lock_class_key __key; \
+ init_timer_deferrable_key((timer), #timer, &__key); \
+ } while (0)
+
+#define init_timer_on_stack(timer) \
+ do { \
+ static struct lock_class_key __key; \
+ init_timer_on_stack_key((timer), #timer, &__key); \
+ } while (0)
+
+#define setup_timer(timer, fn, data) \
+ do { \
+ static struct lock_class_key __key; \
+ setup_timer_key((timer), #timer, &__key, (fn), (data));\
+ } while (0)
+
+#define setup_timer_on_stack(timer, fn, data) \
+ do { \
+ static struct lock_class_key __key; \
+ setup_timer_on_stack_key((timer), #timer, &__key, \
+ (fn), (data)); \
+ } while (0)
+#else
+#define init_timer(timer)\
+ init_timer_key((timer), NULL, NULL)
+#define init_timer_deferrable(timer)\
+ init_timer_deferrable_key((timer), NULL, NULL)
+#define init_timer_on_stack(timer)\
+ init_timer_on_stack_key((timer), NULL, NULL)
+#define setup_timer(timer, fn, data)\
+ 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))
+#endif
#ifdef CONFIG_DEBUG_OBJECTS_TIMERS
-extern void init_timer_on_stack(struct timer_list *timer);
+extern void init_timer_on_stack_key(struct timer_list *timer,
+ const char *name,
+ struct lock_class_key *key);
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)
+static inline void init_timer_on_stack_key(struct timer_list *timer,
+ const char *name,
+ struct lock_class_key *key)
{
- init_timer(timer);
+ init_timer_key(timer, name, key);
}
#endif
-static inline void setup_timer(struct timer_list * timer,
+static inline void setup_timer_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(timer);
+ init_timer_key(timer, name, key);
}
-static inline void setup_timer_on_stack(struct timer_list *timer,
+static inline void setup_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(timer);
+ init_timer_on_stack_key(timer, name, key);
}
/**
--- wireless-testing.orig/kernel/timer.c 2009-01-28 11:33:17.000000000 +0100
+++ wireless-testing/kernel/timer.c 2009-01-28 11:34:26.000000000 +0100
@@ -491,14 +491,18 @@ static inline void debug_timer_free(stru
debug_object_free(timer, &timer_debug_descr);
}
-static void __init_timer(struct timer_list *timer);
-
-void init_timer_on_stack(struct timer_list *timer)
+static void __init_timer(struct timer_list *timer,
+ const char *name,
+ struct lock_class_key *key);
+
+void init_timer_on_stack_key(struct timer_list *timer,
+ const char *name,
+ struct lock_class_key *key)
{
debug_object_init_on_stack(timer, &timer_debug_descr);
- __init_timer(timer);
+ __init_timer(timer, name, key);
}
-EXPORT_SYMBOL_GPL(init_timer_on_stack);
+EXPORT_SYMBOL_GPL(init_timer_on_stack_key);
void destroy_timer_on_stack(struct timer_list *timer)
{
@@ -512,7 +516,9 @@ static inline void debug_timer_activate(
static inline void debug_timer_deactivate(struct timer_list *timer) { }
#endif
-static void __init_timer(struct timer_list *timer)
+static void __init_timer(struct timer_list *timer,
+ const char *name,
+ struct lock_class_key *key)
{
timer->entry.next = NULL;
timer->base = __raw_get_cpu_var(tvec_bases);
@@ -521,6 +527,7 @@ static void __init_timer(struct timer_li
timer->start_pid = -1;
memset(timer->start_comm, 0, TASK_COMM_LEN);
#endif
+ lockdep_init_map(&timer->lockdep_map, name, key, 0);
}
/**
@@ -530,19 +537,23 @@ static void __init_timer(struct timer_li
* init_timer() must be done to a timer prior calling *any* of the
* other timer functions.
*/
-void init_timer(struct timer_list *timer)
+void init_timer_key(struct timer_list *timer,
+ const char *name,
+ struct lock_class_key *key)
{
debug_timer_init(timer);
- __init_timer(timer);
+ __init_timer(timer, name, key);
}
-EXPORT_SYMBOL(init_timer);
+EXPORT_SYMBOL(init_timer_key);
-void init_timer_deferrable(struct timer_list *timer)
+void init_timer_deferrable_key(struct timer_list *timer,
+ const char *name,
+ struct lock_class_key *key)
{
- init_timer(timer);
+ init_timer_key(timer, name, key);
timer_set_deferrable(timer);
}
-EXPORT_SYMBOL(init_timer_deferrable);
+EXPORT_SYMBOL(init_timer_deferrable_key);
static inline void detach_timer(struct timer_list *timer,
int clear_pending)
@@ -789,6 +800,15 @@ EXPORT_SYMBOL(try_to_del_timer_sync);
*/
int del_timer_sync(struct timer_list *timer)
{
+#ifdef CONFIG_LOCKDEP
+ unsigned long flags;
+
+ local_irq_save(flags);
+ lock_map_acquire(&timer->lockdep_map);
+ lock_map_release(&timer->lockdep_map);
+ local_irq_restore(flags);
+#endif
+
for (;;) {
int ret = try_to_del_timer_sync(timer);
if (ret >= 0)
@@ -861,10 +881,36 @@ static inline void __run_timers(struct t
set_running_timer(base, timer);
detach_timer(timer, 1);
+
spin_unlock_irq(&base->lock);
{
int preempt_count = preempt_count();
+
+#ifdef CONFIG_LOCKDEP
+ /*
+ * It is permissible to free the timer from
+ * inside the function that is called from
+ * it, this we need to take into account for
+ * lockdep too. To avoid bogus "held lock
+ * freed" warnings as well as problems when
+ * looking into timer->lockdep_map, make a
+ * copy and use that here.
+ */
+ struct lockdep_map lockdep_map =
+ timer->lockdep_map;
+#endif
+ /*
+ * Couple the lock chain with the lock chain at
+ * del_timer_sync() by acquiring the lock_map
+ * around the fn() call here and in
+ * del_timer_sync().
+ */
+ lock_map_acquire(&lockdep_map);
+
fn(data);
+
+ lock_map_release(&lockdep_map);
+
if (preempt_count != preempt_count()) {
printk(KERN_ERR "huh, entered %p "
"with preempt_count %08x, exited"
--
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