lockdep.c

Kernel code of linux kernel

				break;
		}
		depth--;
		/*
		 * End of lock-stack?
		 */
		if (!depth)
			break;
		/*
		 * Stop the search if we cross into another context:
		 */
		if (curr->held_locks[depth].irq_context !=
				curr->held_locks[depth-1].irq_context)
			break;
	}
	return 1;
out_bug:
	if (!debug_locks_off_graph_unlock())
		return 0;

	WARN_ON(1);

	return 0;
}

unsigned long nr_lock_chains;
struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
int nr_chain_hlocks;
static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];

struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
{
	return lock_classes + chain_hlocks[chain->base + i];
}

/*
 * Look up a dependency chain. If the key is not present yet then
 * add it and return 1 - in this case the new dependency chain is
 * validated. If the key is already hashed, return 0.
 * (On return with 1 graph_lock is held.)
 */
static inline int lookup_chain_cache(struct task_struct *curr,
				     struct held_lock *hlock,
				     u64 chain_key)
{
	struct lock_class *class = hlock_class(hlock);
	struct list_head *hash_head = chainhashentry(chain_key);
	struct lock_chain *chain;
	struct held_lock *hlock_curr, *hlock_next;
	int i, j, n, cn;

	if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
		return 0;
	/*
	 * We can walk it lock-free, because entries only get added
	 * to the hash:
	 */
	list_for_each_entry(chain, hash_head, entry) {
		if (chain->chain_key == chain_key) {
cache_hit:
			debug_atomic_inc(&chain_lookup_hits);
			if (very_verbose(class))
				printk("\nhash chain already cached, key: "
					"%016Lx tail class: [%p] %s\n",
					(unsigned long long)chain_key,
					class->key, class->name);
			return 0;
		}
	}
	if (very_verbose(class))
		printk("\nnew hash chain, key: %016Lx tail class: [%p] %s\n",
			(unsigned long long)chain_key, class->key, class->name);
	/*
	 * Allocate a new chain entry from the static array, and add
	 * it to the hash:
	 */
	if (!graph_lock())
		return 0;
	/*
	 * We have to walk the chain again locked - to avoid duplicates:
	 */
	list_for_each_entry(chain, hash_head, entry) {
		if (chain->chain_key == chain_key) {
			graph_unlock();
			goto cache_hit;
		}
	}
	if (unlikely(nr_lock_chains >= MAX_LOCKDEP_CHAINS)) {
		if (!debug_locks_off_graph_unlock())
			return 0;

		printk("BUG: MAX_LOCKDEP_CHAINS too low!\n");
		printk("turning off the locking correctness validator.\n");
		return 0;
	}
	chain = lock_chains + nr_lock_chains++;
	chain->chain_key = chain_key;
	chain->irq_context = hlock->irq_context;
	/* Find the first held_lock of current chain */
	hlock_next = hlock;
	for (i = curr->lockdep_depth - 1; i >= 0; i--) {
		hlock_curr = curr->held_locks + i;
		if (hlock_curr->irq_context != hlock_next->irq_context)
			break;
		hlock_next = hlock;
	}
	i++;
	chain->depth = curr->lockdep_depth + 1 - i;
	cn = nr_chain_hlocks;
	while (cn + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS) {
		n = cmpxchg(&nr_chain_hlocks, cn, cn + chain->depth);
		if (n == cn)
			break;
		cn = n;
	}
	if (likely(cn + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) {
		chain->base = cn;
		for (j = 0; j < chain->depth - 1; j++, i++) {
			int lock_id = curr->held_locks[i].class_idx - 1;
			chain_hlocks[chain->base + j] = lock_id;
		}
		chain_hlocks[chain->base + j] = class - lock_classes;
	}
	list_add_tail_rcu(&chain->entry, hash_head);
	debug_atomic_inc(&chain_lookup_misses);
	inc_chains();

	return 1;
}

static int validate_chain(struct task_struct *curr, struct lockdep_map *lock,
		struct held_lock *hlock, int chain_head, u64 chain_key)
{
	/*
	 * Trylock needs to maintain the stack of held locks, but it
	 * does not add new dependencies, because trylock can be done
	 * in any order.
	 *
	 * We look up the chain_key and do the O(N^2) check and update of
	 * the dependencies only if this is a new dependency chain.
	 * (If lookup_chain_cache() returns with 1 it acquires
	 * graph_lock for us)
	 */
	if (!hlock->trylock && (hlock->check == 2) &&
	    lookup_chain_cache(curr, hlock, chain_key)) {
		/*
		 * Check whether last held lock:
		 *
		 * - is irq-safe, if this lock is irq-unsafe
		 * - is softirq-safe, if this lock is hardirq-unsafe
		 *
		 * And check whether the new lock's dependency graph
		 * could lead back to the previous lock.
		 *
		 * any of these scenarios could lead to a deadlock. If
		 * All validations
		 */
		int ret = check_deadlock(curr, hlock, lock, hlock->read);

		if (!ret)
			return 0;
		/*
		 * Mark recursive read, as we jump over it when
		 * building dependencies (just like we jump over
		 * trylock entries):
		 */
		if (ret == 2)
			hlock->read = 2;
		/*
		 * Add dependency only if this lock is not the head
		 * of the chain, and if it's not a secondary read-lock:
		 */
		if (!chain_head && ret != 2)
			if (!check_prevs_add(curr, hlock))
				return 0;
		graph_unlock();
	} else
		/* after lookup_chain_cache(): */
		if (unlikely(!debug_locks))
			return 0;

	return 1;
}
#else
static inline int validate_chain(struct task_struct *curr,
	       	struct lockdep_map *lock, struct held_lock *hlock,
		int chain_head, u64 chain_key)
{
	return 1;
}
#endif

/*
 * We are building curr_chain_key incrementally, so double-check
 * it from scratch, to make sure that it's done correctly:
 */
static void check_chain_key(struct task_struct *curr)
{
#ifdef CONFIG_DEBUG_LOCKDEP
	struct held_lock *hlock, *prev_hlock = NULL;
	unsigned int i, id;
	u64 chain_key = 0;

	for (i = 0; i < curr->lockdep_depth; i++) {
		hlock = curr->held_locks + i;
		if (chain_key != hlock->prev_chain_key) {
			debug_locks_off();
			WARN(1, "hm#1, depth: %u [%u], %016Lx != %016Lx\n",
				curr->lockdep_depth, i,
				(unsigned long long)chain_key,
				(unsigned long long)hlock->prev_chain_key);
			return;
		}
		id = hlock->class_idx - 1;
		if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))
			return;

		if (prev_hlock && (prev_hlock->irq_context !=
							hlock->irq_context))
			chain_key = 0;
		chain_key = iterate_chain_key(chain_key, id);
		prev_hlock = hlock;
	}
	if (chain_key != curr->curr_chain_key) {
		debug_locks_off();
		WARN(1, "hm#2, depth: %u [%u], %016Lx != %016Lx\n",
			curr->lockdep_depth, i,
			(unsigned long long)chain_key,
			(unsigned long long)curr->curr_chain_key);
	}
#endif
}

static int
print_usage_bug(struct task_struct *curr, struct held_lock *this,
		enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
{
	if (!debug_locks_off_graph_unlock() || debug_locks_silent)
		return 0;

	printk("\n=================================\n");
	printk(  "[ INFO: inconsistent lock state ]\n");
	print_kernel_version();
	printk(  "---------------------------------\n");

	printk("inconsistent {%s} -> {%s} usage.\n",
		usage_str[prev_bit], usage_str[new_bit]);

	printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] takes:\n",
		curr->comm, task_pid_nr(curr),
		trace_hardirq_context(curr), hardirq_count() >> HARDIRQ_SHIFT,
		trace_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT,
		trace_hardirqs_enabled(curr),
		trace_softirqs_enabled(curr));
	print_lock(this);

	printk("{%s} state was registered at:\n", usage_str[prev_bit]);
	print_stack_trace(hlock_class(this)->usage_traces + prev_bit, 1);

	print_irqtrace_events(curr);
	printk("\nother info that might help us debug this:\n");
	lockdep_print_held_locks(curr);

	printk("\nstack backtrace:\n");
	dump_stack();

	return 0;
}

/*
 * Print out an error if an invalid bit is set:
 */
static inline int
valid_state(struct task_struct *curr, struct held_lock *this,
	    enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit)
{
	if (unlikely(hlock_class(this)->usage_mask & (1 << bad_bit)))
		return print_usage_bug(curr, this, bad_bit, new_bit);
	return 1;
}

static int mark_lock(struct task_struct *curr, struct held_lock *this,
		     enum lock_usage_bit new_bit);

#if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)

/*
 * print irq inversion bug:
 */
static int
print_irq_inversion_bug(struct task_struct *curr, struct lock_class *other,
			struct held_lock *this, int forwards,
			const char *irqclass)
{
	if (!debug_locks_off_graph_unlock() || debug_locks_silent)
		return 0;

	printk("\n=========================================================\n");
	printk(  "[ INFO: possible irq lock inversion dependency detected ]\n");
	print_kernel_version();
	printk(  "---------------------------------------------------------\n");
	printk("%s/%d just changed the state of lock:\n",
		curr->comm, task_pid_nr(curr));
	print_lock(this);
	if (forwards)
		printk("but this lock took another, %s-irq-unsafe lock in the past:\n", irqclass);
	else
		printk("but this lock was taken by another, %s-irq-safe lock in the past:\n", irqclass);
	print_lock_name(other);
	printk("\n\nand interrupts could create inverse lock ordering between them.\n\n");

	printk("\nother info that might help us debug this:\n");
	lockdep_print_held_locks(curr);

	printk("\nthe first lock's dependencies:\n");
	print_lock_dependencies(hlock_class(this), 0);

	printk("\nthe second lock's dependencies:\n");
	print_lock_dependencies(other, 0);

	printk("\nstack backtrace:\n");
	dump_stack();

	return 0;
}

/*
 * Prove that in the forwards-direction subgraph starting at <this>
 * there is no lock matching <mask>:
 */
static int
check_usage_forwards(struct task_struct *curr, struct held_lock *this,
		     enum lock_usage_bit bit, const char *irqclass)
{
	int ret;

	find_usage_bit = bit;
	/* fills in <forwards_match> */
	ret = find_usage_forwards(hlock_class(this), 0);
	if (!ret || ret == 1)
		return ret;

	return print_irq_inversion_bug(curr, forwards_match, this, 1, irqclass);
}

/*
 * Prove that in the backwards-direction subgraph starting at <this>
 * there is no lock matching <mask>:
 */
static int
check_usage_backwards(struct task_struct *curr, struct held_lock *this,
		      enum lock_usage_bit bit, const char *irqclass)
{
	int ret;

	find_usage_bit = bit;
	/* fills in <backwards_match> */
	ret = find_usage_backwards(hlock_class(this), 0);
	if (!ret || ret == 1)
		return ret;

	return print_irq_inversion_bug(curr, backwards_match, this, 0, irqclass);
}

void print_irqtrace_events(struct task_struct *curr)
{
	printk("irq event stamp: %u\n", curr->irq_events);
	printk("hardirqs last  enabled at (%u): ", curr->hardirq_enable_event);
	print_ip_sym(curr->hardirq_enable_ip);
	printk("hardirqs last disabled at (%u): ", curr->hardirq_disable_event);
	print_ip_sym(curr->hardirq_disable_ip);
	printk("softirqs last  enabled at (%u): ", curr->softirq_enable_event);
	print_ip_sym(curr->softirq_enable_ip);
	printk("softirqs last disabled at (%u): ", curr->softirq_disable_event);
	print_ip_sym(curr->softirq_disable_ip);
}

static int hardirq_verbose(struct lock_class *class)
{
#if HARDIRQ_VERBOSE
	return class_filter(class);
#endif
	return 0;
}

static int softirq_verbose(struct lock_class *class)
{
#if SOFTIRQ_VERBOSE
	return class_filter(class);
#endif
	return 0;
}

#define STRICT_READ_CHECKS	1

static int mark_lock_irq(struct task_struct *curr, struct held_lock *this,
		enum lock_usage_bit new_bit)
{
	int ret = 1;

	switch(new_bit) {
	case LOCK_USED_IN_HARDIRQ:
		if (!valid_state(curr, this, new_bit, LOCK_ENABLED_HARDIRQS))
			return 0;
		if (!valid_state(curr, this, new_bit,
				 LOCK_ENABLED_HARDIRQS_READ))
			return 0;
		/*
		 * just marked it hardirq-safe, check that this lock
		 * took no hardirq-unsafe lock in the past:
		 */
		if (!check_usage_forwards(curr, this,
					  LOCK_ENABLED_HARDIRQS, "hard"))
			return 0;
#if STRICT_READ_CHECKS
		/*
		 * just marked it hardirq-safe, check that this lock
		 * took no hardirq-unsafe-read lock in the past:
		 */
		if (!check_usage_forwards(curr, this,
				LOCK_ENABLED_HARDIRQS_READ, "hard-read"))
			return 0;
#endif
		if (hardirq_verbose(hlock_class(this)))
			ret = 2;
		break;
	case LOCK_USED_IN_SOFTIRQ:
		if (!valid_state(curr, this, new_bit, LOCK_ENABLED_SOFTIRQS))
			return 0;
		if (!valid_state(curr, this, new_bit,
				 LOCK_ENABLED_SOFTIRQS_READ))
			return 0;
		/*
		 * just marked it softirq-safe, check that this lock
		 * took no softirq-unsafe lock in the past:
		 */
		if (!check_usage_forwards(curr, this,
					  LOCK_ENABLED_SOFTIRQS, "soft"))
			return 0;
#if STRICT_READ_CHECKS
		/*
		 * just marked it softirq-safe, check that this lock
		 * took no softirq-unsafe-read lock in the past:
		 */
		if (!check_usage_forwards(curr, this,
				LOCK_ENABLED_SOFTIRQS_READ, "soft-read"))
			return 0;
#endif
		if (softirq_verbose(hlock_class(this)))
			ret = 2;
		break;
	case LOCK_USED_IN_HARDIRQ_READ:
		if (!valid_state(curr, this, new_bit, LOCK_ENABLED_HARDIRQS))
			return 0;
		/*
		 * just marked it hardirq-read-safe, check that this lock
		 * took no hardirq-unsafe lock in the past:
		 */
		if (!check_usage_forwards(curr, this,
					  LOCK_ENABLED_HARDIRQS, "hard"))
			return 0;
		if (hardirq_verbose(hlock_class(this)))
			ret = 2;
		break;
	case LOCK_USED_IN_SOFTIRQ_READ:
		if (!valid_state(curr, this, new_bit, LOCK_ENABLED_SOFTIRQS))
			return 0;
		/*
		 * just marked it softirq-read-safe, check that this lock
		 * took no softirq-unsafe lock in the past:
		 */
		if (!check_usage_forwards(curr, this,
					  LOCK_ENABLED_SOFTIRQS, "soft"))
			return 0;
		if (softirq_verbose(hlock_class(this)))
			ret = 2;
		break;
	case LOCK_ENABLED_HARDIRQS:
		if (!valid_state(curr, this, new_bit, LOCK_USED_IN_HARDIRQ))
			return 0;
		if (!valid_state(curr, this, new_bit,
				 LOCK_USED_IN_HARDIRQ_READ))
			return 0;
		/*
		 * just marked it hardirq-unsafe, check that no hardirq-safe
		 * lock in the system ever took it in the past:
		 */
		if (!check_usage_backwards(curr, this,
					   LOCK_USED_IN_HARDIRQ, "hard"))
			return 0;
#if STRICT_READ_CHECKS
		/*
		 * just marked it hardirq-unsafe, check that no
		 * hardirq-safe-read lock in the system ever took
		 * it in the past:
		 */
		if (!check_usage_backwards(curr, this,
				   LOCK_USED_IN_HARDIRQ_READ, "hard-read"))
			return 0;
#endif
		if (hardirq_verbose(hlock_class(this)))
			ret = 2;
		break;
	case LOCK_ENABLED_SOFTIRQS:
		if (!valid_state(curr, this, new_bit, LOCK_USED_IN_SOFTIRQ))
			return 0;
		if (!valid_state(curr, this, new_bit,
				 LOCK_USED_IN_SOFTIRQ_READ))
			return 0;
		/*
		 * just marked it softirq-unsafe, check that no softirq-safe
		 * lock in the system ever took it in the past:
		 */
		if (!check_usage_backwards(curr, this,
					   LOCK_USED_IN_SOFTIRQ, "soft"))
			return 0;
#if STRICT_READ_CHECKS
		/*