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Commit de4643a7 authored by Bart Van Assche's avatar Bart Van Assche Committed by Ingo Molnar
Browse files

locking/lockdep: Reuse lock chains that have been freed 



A previous patch introduced a lock chain leak. Fix that leak by reusing
lock chains that have been freed.

Signed-off-by: default avatarBart Van Assche <bvanassche@acm.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: johannes.berg@intel.com
Cc: tj@kernel.org
Link: https://lkml.kernel.org/r/20190214230058.196511-16-bvanassche@acm.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 527af3ea

kernel/locking/lockdep.c

+37 −20
Original line number Diff line number Diff line
@@ -292,9 +292,12 @@ static LIST_HEAD(free_lock_classes); 
/**

 * struct pending_free - information about data structures about to be freed

 * @zapped: Head of a list with struct lock_class elements.

 * @lock_chains_being_freed: Bitmap that indicates which lock_chains[] elements

 *	are about to be freed.

 */

struct pending_free {

	struct list_head zapped;

	DECLARE_BITMAP(lock_chains_being_freed, MAX_LOCKDEP_CHAINS);

};



/**
@@ -2096,8 +2099,8 @@ check_prevs_add(struct task_struct *curr, struct held_lock *next) 
	return 0;

}



static unsigned long nr_lock_chains;

struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];

static DECLARE_BITMAP(lock_chains_in_use, MAX_LOCKDEP_CHAINS);

int nr_chain_hlocks;

static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
@@ -2236,12 +2239,25 @@ static int check_no_collision(struct task_struct *curr, 
 */

long lockdep_next_lockchain(long i)

{

	return i + 1 < nr_lock_chains ? i + 1 : -2;

	i = find_next_bit(lock_chains_in_use, ARRAY_SIZE(lock_chains), i + 1);

	return i < ARRAY_SIZE(lock_chains) ? i : -2;

}



unsigned long lock_chain_count(void)

{

	return nr_lock_chains;

	return bitmap_weight(lock_chains_in_use, ARRAY_SIZE(lock_chains));

}



/* Must be called with the graph lock held. */

static struct lock_chain *alloc_lock_chain(void)

{

	int idx = find_first_zero_bit(lock_chains_in_use,

				      ARRAY_SIZE(lock_chains));



	if (unlikely(idx >= ARRAY_SIZE(lock_chains)))

		return NULL;

	__set_bit(idx, lock_chains_in_use);

	return lock_chains + idx;

}



/*
@@ -2260,11 +2276,6 @@ static inline int add_chain_cache(struct task_struct *curr, 
	struct lock_chain *chain;

	int i, j;



	/*

	 * Allocate a new chain entry from the static array, and add

	 * it to the hash:

	 */



	/*

	 * The caller must hold the graph lock, ensure we've got IRQs

	 * disabled to make this an IRQ-safe lock.. for recursion reasons
@@ -2273,7 +2284,8 @@ static inline int add_chain_cache(struct task_struct *curr, 
	if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))

		return 0;



	if (unlikely(nr_lock_chains >= MAX_LOCKDEP_CHAINS)) {

	chain = alloc_lock_chain();

	if (!chain) {

		if (!debug_locks_off_graph_unlock())

			return 0;
@@ -2281,7 +2293,6 @@ static inline int add_chain_cache(struct task_struct *curr, 
		dump_stack();

		return 0;

	}

	chain = lock_chains + nr_lock_chains++;

	chain->chain_key = chain_key;

	chain->irq_context = hlock->irq_context;

	i = get_first_held_lock(curr, hlock);
@@ -4208,7 +4219,8 @@ void lockdep_reset(void) 
}



/* Remove a class from a lock chain. Must be called with the graph lock held. */

static void remove_class_from_lock_chain(struct lock_chain *chain,

static void remove_class_from_lock_chain(struct pending_free *pf,

					 struct lock_chain *chain,

					 struct lock_class *class)

{

#ifdef CONFIG_PROVE_LOCKING
@@ -4246,6 +4258,7 @@ static void remove_class_from_lock_chain(struct lock_chain *chain, 
	 * hlist_for_each_entry_rcu() loop is safe.

	 */

	hlist_del_rcu(&chain->entry);

	__set_bit(chain - lock_chains, pf->lock_chains_being_freed);

	if (chain->depth == 0)

		return;

	/*
@@ -4254,22 +4267,19 @@ static void remove_class_from_lock_chain(struct lock_chain *chain, 
	 */

	if (lookup_chain_cache(chain_key))

		return;

	if (WARN_ON_ONCE(nr_lock_chains >= MAX_LOCKDEP_CHAINS)) {

	new_chain = alloc_lock_chain();

	if (WARN_ON_ONCE(!new_chain)) {

		debug_locks_off();

		return;

	}

	/*

	 * Leak *chain because it is not safe to reinsert it before an RCU

	 * grace period has expired.

	 */

	new_chain = lock_chains + nr_lock_chains++;

	*new_chain = *chain;

	hlist_add_head_rcu(&new_chain->entry, chainhashentry(chain_key));

#endif

}



/* Must be called with the graph lock held. */

static void remove_class_from_lock_chains(struct lock_class *class)

static void remove_class_from_lock_chains(struct pending_free *pf,

					  struct lock_class *class)

{

	struct lock_chain *chain;

	struct hlist_head *head;
@@ -4278,7 +4288,7 @@ static void remove_class_from_lock_chains(struct lock_class *class) 
	for (i = 0; i < ARRAY_SIZE(chainhash_table); i++) {

		head = chainhash_table + i;

		hlist_for_each_entry_rcu(chain, head, entry) {

			remove_class_from_lock_chain(chain, class);

			remove_class_from_lock_chain(pf, chain, class);

		}

	}

}
@@ -4317,7 +4327,7 @@ static void zap_class(struct pending_free *pf, struct lock_class *class) 
			  class->name);

	}



	remove_class_from_lock_chains(class);

	remove_class_from_lock_chains(pf, class);

}



static void reinit_class(struct lock_class *class)
@@ -4383,6 +4393,12 @@ static void __free_zapped_classes(struct pending_free *pf) 
		reinit_class(class);



	list_splice_init(&pf->zapped, &free_lock_classes);



#ifdef CONFIG_PROVE_LOCKING

	bitmap_andnot(lock_chains_in_use, lock_chains_in_use,

		      pf->lock_chains_being_freed, ARRAY_SIZE(lock_chains));

	bitmap_clear(pf->lock_chains_being_freed, 0, ARRAY_SIZE(lock_chains));

#endif

}



static void free_zapped_rcu(struct rcu_head *ch)
@@ -4623,6 +4639,7 @@ void __init lockdep_init(void) 
#ifdef CONFIG_PROVE_LOCKING

		+ sizeof(lock_cq)

		+ sizeof(lock_chains)

		+ sizeof(lock_chains_in_use)

		+ sizeof(chain_hlocks)

#endif

		) / 1024