Commit-ID: de4643a77356a77bce73f64275b125b4b71a69cf Gitweb: https://git.kernel.org/tip/de4643a77356a77bce73f64275b125b4b71a69cf Author: Bart Van Assche <bvanass...@acm.org> AuthorDate: Thu, 14 Feb 2019 15:00:50 -0800 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Thu, 28 Feb 2019 07:55:45 +0100
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: Bart Van Assche <bvanass...@acm.org> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> Cc: Andrew Morton <a...@linux-foundation.org> Cc: Johannes Berg <johan...@sipsolutions.net> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Paul E. McKenney <paul...@linux.vnet.ibm.com> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Thomas Gleixner <t...@linutronix.de> Cc: Waiman Long <long...@redhat.com> Cc: Will Deacon <will.dea...@arm.com> Cc: johannes.b...@intel.com Cc: t...@kernel.org Link: https://lkml.kernel.org/r/20190214230058.196511-16-bvanass...@acm.org Signed-off-by: Ingo Molnar <mi...@kernel.org> --- kernel/locking/lockdep.c | 57 +++++++++++++++++++++++++++++++----------------- 1 file changed, 37 insertions(+), 20 deletions(-) diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index ec0cb794f70d..0bb204464afe 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -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 @@ out_bug: 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 @@ recalc: * 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 @@ recalc: */ 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
