path: root/lib/debugobjects.c

/*
 * Generic infrastructure for lifetime debugging of objects.
 *
 * Started by Thomas Gleixner
 *
 * Copyright (C) 2008, Thomas Gleixner <tglx@linutronix.de>
 *
 * For licencing details see kernel-base/COPYING
 */
#include <linux/debugobjects.h>
#include <linux/interrupt.h>
#include <linux/seq_file.h>
#include <linux/debugfs.h>
#include <linux/hash.h>

#define ODEBUG_HASH_BITS	14
#define ODEBUG_HASH_SIZE	(1 << ODEBUG_HASH_BITS)

#define ODEBUG_POOL_SIZE	512
#define ODEBUG_POOL_MIN_LEVEL	256

#define ODEBUG_CHUNK_SHIFT	PAGE_SHIFT
#define ODEBUG_CHUNK_SIZE	(1 << ODEBUG_CHUNK_SHIFT)
#define ODEBUG_CHUNK_MASK	(~(ODEBUG_CHUNK_SIZE - 1))

struct debug_bucket {
	struct hlist_head	list;
	spinlock_t		lock;
};

static struct debug_bucket	obj_hash[ODEBUG_HASH_SIZE];

static struct debug_obj		obj_static_pool[ODEBUG_POOL_SIZE];

static DEFINE_SPINLOCK(pool_lock);

static HLIST_HEAD(obj_pool);

static int			obj_pool_min_free = ODEBUG_POOL_SIZE;
static int			obj_pool_free = ODEBUG_POOL_SIZE;
static int			obj_pool_used;
static int			obj_pool_max_used;
static struct kmem_cache	*obj_cache;

static int			debug_objects_maxchain __read_mostly;
static int			debug_objects_fixups __read_mostly;
static int			debug_objects_warnings __read_mostly;
static int			debug_objects_enabled __read_mostly;
static struct debug_obj_descr	*descr_test  __read_mostly;

static int __init enable_object_debug(char *str)
{
	debug_objects_enabled = 1;
	return 0;
}
early_param("debug_objects", enable_object_debug);

static const char *obj_states[ODEBUG_STATE_MAX] = {
	[ODEBUG_STATE_NONE]		= "none",
	[ODEBUG_STATE_INIT]		= "initialized",
	[ODEBUG_STATE_INACTIVE]		= "inactive",
	[ODEBUG_STATE_ACTIVE]		= "active",
	[ODEBUG_STATE_DESTROYED]	= "destroyed",
	[ODEBUG_STATE_NOTAVAILABLE]	= "not available",
};

static int fill_pool(void)
{
	gfp_t gfp = GFP_ATOMIC | __GFP_NORETRY | __GFP_NOWARN;
	struct debug_obj *new;

	if (likely(obj_pool_free >= ODEBUG_POOL_MIN_LEVEL))
		return obj_pool_free;

	if (unlikely(!obj_cache))
		return obj_pool_free;

	while (obj_pool_free < ODEBUG_POOL_MIN_LEVEL) {

		new = kmem_cache_zalloc(obj_cache, gfp);
		if (!new)
			return obj_pool_free;

		spin_lock(&pool_lock);
		hlist_add_head(&new->node, &obj_pool);
		obj_pool_free++;
		spin_unlock(&pool_lock);
	}
	return obj_pool_free;
}

/*
 * Lookup an object in the hash bucket.
 */
static struct debug_obj *lookup_object(void *addr, struct debug_bucket *b)
{
	struct hlist_node *node;
	struct debug_obj *obj;
	int cnt = 0;

	hlist_for_each_entry(obj, node, &b->list, node) {
		cnt++;
		if (obj->object == addr)
			return obj;
	}
	if (cnt > debug_objects_maxchain)
		debug_objects_maxchain = cnt;

	return NULL;
}

/*
 * Allocate a new object. If the pool is empty and no refill possible,
 * switch off the debugger.
 */
static struct debug_obj *
alloc_object(void *addr, struct debug_bucket *b, struct debug_obj_descr *descr)
{
	struct debug_obj *obj = NULL;
	int retry = 0;

repeat:
	spin_lock(&pool_lock);
	if (obj_pool.first) {
		obj	    = hlist_entry(obj_pool.first, typeof(*obj), node);

		obj->object = addr;
		obj->descr  = descr;
		obj->state  = ODEBUG_STATE_NONE;
		hlist_del(&obj->node);

		hlist_add_head(&obj->node, &b->list);

		obj_pool_used++;
		if (obj_pool_used > obj_pool_max_used)
			obj_pool_max_used = obj_pool_used;

		obj_pool_free--;
		if (obj_pool_free < obj_pool_min_free)
			obj_pool_min_free = obj_pool_free;
	}
	spin_unlock(&pool_lock);

	if (fill_pool() && !obj && !retry++)
		goto repeat;

	return obj;
}

/*
 * Put the object back into the pool or give it back to kmem_cache:
 */
static void free_object(struct debug_obj *obj)
{
	unsigned long idx = (unsigned long)(obj - obj_static_pool);

	if (obj_pool_free < ODEBUG_POOL_SIZE || idx < ODEBUG_POOL_SIZE) {
		spin_lock(&pool_lock);
		hlist_add_head(&obj->node, &obj_pool);
		obj_pool_free++;
		obj_pool_used--;
		spin_unlock(&pool_lock);
	} else {
		spin_lock(&pool_lock);
		obj_pool_used--;
		spin_unlock(&pool_lock);
		kmem_cache_free(obj_cache, obj);
	}
}

/*
 * We run out of memory. That means we probably have tons of objects
 * allocated.
 */
static void debug_objects_oom(void)
{
	struct debug_bucket *db = obj_hash;
	struct hlist_node *node, *tmp;
	struct debug_obj *obj;
	unsigned long flags;
	int i;

	printk(KERN_WARNING "ODEBUG: Out of memory. ODEBUG disabled\n");

	for (i = 0; i < ODEBUG_HASH_SIZE; i++, db++) {
		spin_lock_irqsave(&db->lock, flags);