[patch 2/2] add timer specific object debugging code

Thomas Gleixner
2008-03-01T10:26:00Z

[-- Attachment #1: timer-debugging.patch --]
[-- Type: text/plain, Size: 7033 bytes --]

Add calls to the generic object debugging infrastructure and provide a
fixup function which allows to keep the system alive when recoverable
problems have been detected by the object debugging core code. Add a
selftest, which covers the two possible mistakes: free/init of an
active timer.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
include/linux/debugobjects.h | 1
include/linux/timer.h | 22 +++++++++++
kernel/timer.c | 85 +++++++++++++++++++++++++++++++++++++++++++
lib/Kconfig.debug | 7 +++
lib/debugobjects.c | 18 ++++++++-
5 files changed, 131 insertions(+), 2 deletions(-)

Index: linux-2.6/include/linux/debugobjects.h
===================================================================
--- linux-2.6.orig/include/linux/debugobjects.h
+++ linux-2.6/include/linux/debugobjects.h
@@ -14,6 +14,7 @@ enum debug_obj_op {

enum {
ODEBUG_TYPE_UNKNOWN,
+ ODEBUG_TYPE_TIMER,
ODEBUG_MAX_TYPES
};

Index: linux-2.6/include/linux/timer.h
===================================================================
--- linux-2.6.orig/include/linux/timer.h
+++ linux-2.6/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;

@@ -20,6 +21,9 @@ struct timer_list {
char start_comm[16];
int start_pid;
#endif
+#ifdef CONFIG_DEBUG_OBJECT_TIMERS
+ struct debug_obj dobj;
+#endif
};

extern struct tvec_base boot_tvec_bases;
@@ -164,5 +168,23 @@ unsigned long __round_jiffies_relative(u
unsigned long round_jiffies(unsigned long j);
unsigned long round_jiffies_relative(unsigned long j);

+#ifdef CONFIG_DEBUG_OBJECT_TIMERS
+static inline void
+debug_timer_object_op(struct timer_list *timer, enum debug_obj_op mode)
+{
+ timer->dobj.type = ODEBUG_TYPE_TIMER;
+ debug_object_op(&timer->dobj, mode);
+}
+extern int timer_fixup_object(struct debug_obj *obj, enum debug_obj_op mode);
+extern int timer_debug_object_selftest(void);
+#else
+static inline void
+debug_timer_object_op(struct timer_list *timer, enum debug_obj_op mode)
+{
+}
+# define timer_fixup_object NULL
+static inline int timer_debug_object_selftest(void) { return 0; }
+#endif
+

#endif
Index: linux-2.6/kernel/timer.c
===================================================================
--- linux-2.6.orig/kernel/timer.c
+++ linux-2.6/kernel/timer.c
@@ -320,6 +320,84 @@ static void timer_stats_account_timer(st
static void timer_stats_account_timer(struct timer_list *timer) {}
#endif

+#ifdef CONFIG_DEBUG_OBJECT_TIMERS
+
+static int timer_fixup_done __read_mostly;
+
+int timer_fixup_object(struct debug_obj *obj, enum debug_obj_op op)
+{
+ struct timer_list *timer = container_of(obj, struct timer_list, dobj);
+
+ switch (op) {
+ case ODEBUG_INIT:
+ case ODEBUG_FREE:
+ del_timer_sync(timer);
+ timer_fixup_done++;
+ return 0;
+ /*
+ * These are fatal timer.c internal errors. No real way to
+ * survive:
+ */
+ case ODEBUG_ADD:
+ case ODEBUG_DEL:
+ return -1;
+ default:
+ return -1;
+ }
+}
+
+/*
+ * Test the two popular bugs:
+ *
+ * - reinit a timer which is enqueued
+ * - free a datastructure which contains an enqueued timer
+ */
+
+static void __init timer_debug_selftest_fn(unsigned long arg)
+{
+}
+
+int __init timer_debug_object_selftest(void)
+{
+ struct timer_list *timer;
+ int fixup_cnt = timer_fixup_done;
+
+ timer = kmalloc(sizeof(struct timer_list), GFP_KERNEL);
+ if (!timer)
+ return -ENOMEM;
+
+ setup_timer(timer, timer_debug_selftest_fn, 0);
+
+ timer->expires = jiffies + HZ;
+ add_timer(timer);
+
+ setup_timer(timer, timer_debug_selftest_fn, 0);
+ if (fixup_cnt == timer_fixup_done)
+ goto err;
+
+#ifdef CONFIG_DEBUG_OBJECTS_FREE
+ timer->expires = jiffies + HZ;
+ add_timer(timer);
+
+ fixup_cnt = timer_fixup_done;
+ kfree(timer);
+ timer = NULL;
+
+ if (fixup_cnt == timer_fixup_done)
+ goto err;
+#else
+ kfree(timer);
+#endif
+ return 0;
+
+err:
+ printk(KERN_ERR "TIMER: ODEBUG selftest failed\n");
+ kfree(timer);
+ return -1;
+}
+
+#endif
+
/**
* init_timer - initialize a timer.
* @timer: the timer to be initialized
@@ -329,6 +407,8 @@ static void timer_stats_account_timer(st
*/
void init_timer(struct timer_list *timer)
{
+ debug_timer_object_op(timer, ODEBUG_INIT);
+
timer->entry.next = NULL;
timer->base = __raw_get_cpu_var(tvec_bases);
#ifdef CONFIG_TIMER_STATS
@@ -351,6 +431,8 @@ static inline void detach_timer(struct t
{
struct list_head *entry = &timer->entry;

+ debug_timer_object_op(timer, ODEBUG_DEL);
+
__list_del(entry->prev, entry->next);
if (clear_pending)
entry->next = NULL;
@@ -405,6 +487,8 @@ int __mod_timer(struct timer_list *timer
ret = 1;
}

+ debug_timer_object_op(timer, ODEBUG_ADD);
+
new_base = __get_cpu_var(tvec_bases);

if (base != new_base) {
@@ -450,6 +534,7 @@ void add_timer_on(struct timer_list *tim
BUG_ON(timer_pending(timer) || !timer->function);
spin_lock_irqsave(&base->lock, flags);
timer_set_base(timer, base);
+ debug_timer_object_op(timer, ODEBUG_ADD);
internal_add_timer(base, timer);
spin_unlock_irqrestore(&base->lock, flags);
}
Index: linux-2.6/lib/Kconfig.debug
===================================================================
--- linux-2.6.orig/lib/Kconfig.debug
+++ linux-2.6/lib/Kconfig.debug
@@ -199,6 +199,13 @@ config DEBUG_OBJECT_FREE
properly. This can make kmalloc/kfree-intensive workloads
much slower.

+config DEBUG_OBJECT_TIMERS
+ bool "Debug timer objects"
+ depends on DEBUG_OBJECT_OPS
+ help
+ If you say Y here, additional code will be inserted into the
+ timer routines to validate the timer operations.
+
config DEBUG_SLAB
bool "Debug slab memory allocations"
depends on DEBUG_KERNEL && SLAB
Index: linux-2.6/lib/debugobjects.c
===================================================================
--- linux-2.6.orig/lib/debugobjects.c
+++ linux-2.6/lib/debugobjects.c
@@ -12,6 +12,7 @@
#include <linux/debugfs.h>
#include <linux/debugobjects.h>
#include <linux/seq_file.h>
+#include <linux/timer.h>

#define ODEBUG_HASH_SIZE 4096
#define ODEBUG_HASH_MASK (ODEBUG_HASH_SIZE - 1)
@@ -48,11 +49,13 @@ static struct odebug *object_get_hash(un
}

static const void * const debug_fixup[ODEBUG_MAX_TYPES] = {
+ [ODEBUG_TYPE_TIMER] = timer_fixup_object,
};

static const char * const obj_types[ODEBUG_MAX_TYPES] = {

[ODEBUG_TYPE_UNKNOWN] = "unknown type",
+ [ODEBUG_TYPE_TIMER] = "timer_list",
};

static void debug_print_object(struct debug_obj *obj, char *msg)
@@ -246,11 +249,22 @@ void __init debug_objects_init(void)

int __init debug_objects_do_selftest(void)
{
+ int res;
+
if (!debug_objects_enabled)
return 0;

debug_objects_init_debugfs();
- printk(KERN_INFO "ODEBUG: Selftest pass\n");
- return 0;
+
+ debug_objects_selftest = 1;
+
+ res = timer_debug_object_selftest();
+
+ debug_objects_selftest = 0;
+
+ if (!res)
+ printk(KERN_INFO "ODEBUG: Selftest pass\n");
+
+ return res;
}
__initcall(debug_objects_do_selftest);

--