A previous patch introduced a lock chain leak. Fix that leak by reusing lock chains that have been freed.
Cc: Peter Zijlstra <[email protected]> Cc: Waiman Long <[email protected]> Cc: Johannes Berg <[email protected]> Signed-off-by: Bart Van Assche <[email protected]> --- kernel/locking/lockdep.c | 48 +++++++++++++++++++++++++++------------- 1 file changed, 33 insertions(+), 15 deletions(-) diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index cdab3831beb2..8ba326c68253 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -299,6 +299,7 @@ static struct pending_free { struct rcu_head rcu_head; bool scheduled; DECLARE_BITMAP(list_entries_being_freed, MAX_LOCKDEP_ENTRIES); + DECLARE_BITMAP(lock_chains_being_freed, MAX_LOCKDEP_CHAINS); } pending_free[2]; static DECLARE_WAIT_QUEUE_HEAD(rcu_cb); @@ -2092,8 +2093,8 @@ 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]; @@ -2232,12 +2233,25 @@ 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; } /* @@ -2269,7 +2283,8 @@ 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; @@ -2277,7 +2292,6 @@ 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); @@ -4214,7 +4228,8 @@ 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 @@ -4252,6 +4267,7 @@ 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; /* @@ -4260,22 +4276,19 @@ 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; @@ -4284,7 +4297,7 @@ 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); } } } @@ -4324,7 +4337,7 @@ 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) @@ -4373,6 +4386,11 @@ static void free_zapped_classes(struct rcu_head *ch) bitmap_andnot(list_entries_in_use, list_entries_in_use, pf->list_entries_being_freed, ARRAY_SIZE(list_entries)); bitmap_clear(pf->list_entries_being_freed, 0, ARRAY_SIZE(list_entries)); +#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 graph_unlock(); restore_irqs: raw_local_irq_restore(flags); -- 2.20.0.rc2.403.gdbc3b29805-goog
