Messages in this thread Patch in this message | | | From | Waiman Long <> | Subject | [PATCH 2/5] locking/lockdep: Track leaked chain_hlocks entries | Date | Thu, 12 Dec 2019 17:35:22 -0500 |
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If a lock chain contains a class that is zapped, the whole lock chain is now invalid. There is no point in keeping a partial chain behind hoping it can be useful. So just dump the corresponding chain_hlocks entries and account for them in a new nr_leaked_chain_hlocks stat counter which is shown as part of /proc/lockdep_stats.
This patch also changes the type of nr_chain_hlocks to unsigned integer to be consistent with the other counters.
A latter patch will try to reuse the freed chain_hlocks entries.
Signed-off-by: Waiman Long <longman@redhat.com> --- kernel/locking/lockdep.c | 40 ++++++------------------------ kernel/locking/lockdep_internals.h | 5 ++-- kernel/locking/lockdep_proc.c | 4 ++- 3 files changed, 14 insertions(+), 35 deletions(-)
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index c8d0374101b0..d03503b348f1 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -2624,8 +2624,9 @@ check_prevs_add(struct task_struct *curr, struct held_lock *next) 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]; +unsigned int nr_chain_hlocks; +unsigned int nr_leaked_chain_hlocks; struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i) { @@ -4770,57 +4771,32 @@ static void remove_class_from_lock_chain(struct pending_free *pf, struct lock_class *class) { #ifdef CONFIG_PROVE_LOCKING - struct lock_chain *new_chain; - u64 chain_key; int i; for (i = chain->base; i < chain->base + chain->depth; i++) { if (chain_hlocks[i] != class - lock_classes) continue; - /* The code below leaks one chain_hlock[] entry. */ - if (--chain->depth > 0) { - memmove(&chain_hlocks[i], &chain_hlocks[i + 1], - (chain->base + chain->depth - i) * - sizeof(chain_hlocks[0])); - } + /* Account for leaked chain_hlock[] entries. */ + nr_leaked_chain_hlocks += chain->depth; + /* * Each lock class occurs at most once in a lock chain so once * we found a match we can break out of this loop. */ - goto recalc; + goto free_lock_chain; } /* Since the chain has not been modified, return. */ return; -recalc: - chain_key = INITIAL_CHAIN_KEY; - for (i = chain->base; i < chain->base + chain->depth; i++) - chain_key = iterate_chain_key(chain_key, chain_hlocks[i]); - if (chain->depth && chain->chain_key == chain_key) - return; +free_lock_chain: /* Overwrite the chain key for concurrent RCU readers. */ - WRITE_ONCE(chain->chain_key, chain_key); + WRITE_ONCE(chain->chain_key, INITIAL_CHAIN_KEY); /* * Note: calling hlist_del_rcu() from inside a * 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; - /* - * If the modified lock chain matches an existing lock chain, drop - * the modified lock chain. - */ - if (lookup_chain_cache(chain_key)) - return; - new_chain = alloc_lock_chain(); - if (WARN_ON_ONCE(!new_chain)) { - debug_locks_off(); - return; - } - *new_chain = *chain; - hlist_add_head_rcu(&new_chain->entry, chainhashentry(chain_key)); #endif } diff --git a/kernel/locking/lockdep_internals.h b/kernel/locking/lockdep_internals.h index a31d16fd3c43..b6ec9595ae88 100644 --- a/kernel/locking/lockdep_internals.h +++ b/kernel/locking/lockdep_internals.h @@ -128,14 +128,15 @@ extern unsigned long nr_zapped_classes; extern unsigned long nr_list_entries; long lockdep_next_lockchain(long i); unsigned long lock_chain_count(void); -extern int nr_chain_hlocks; extern unsigned long nr_stack_trace_entries; extern unsigned int nr_hardirq_chains; extern unsigned int nr_softirq_chains; extern unsigned int nr_process_chains; -extern unsigned int max_lockdep_depth; +extern unsigned int nr_chain_hlocks; +extern unsigned int nr_leaked_chain_hlocks; +extern unsigned int max_lockdep_depth; extern unsigned int max_bfs_queue_depth; #ifdef CONFIG_PROVE_LOCKING diff --git a/kernel/locking/lockdep_proc.c b/kernel/locking/lockdep_proc.c index 82579fd7469f..aab524530115 100644 --- a/kernel/locking/lockdep_proc.c +++ b/kernel/locking/lockdep_proc.c @@ -271,7 +271,7 @@ static int lockdep_stats_show(struct seq_file *m, void *v) #ifdef CONFIG_PROVE_LOCKING seq_printf(m, " dependency chains: %11lu [max: %lu]\n", lock_chain_count(), MAX_LOCKDEP_CHAINS); - seq_printf(m, " dependency chain hlocks: %11d [max: %lu]\n", + seq_printf(m, " dependency chain hlocks: %11u [max: %lu]\n", nr_chain_hlocks, MAX_LOCKDEP_CHAIN_HLOCKS); #endif @@ -345,6 +345,8 @@ static int lockdep_stats_show(struct seq_file *m, void *v) seq_puts(m, "\n"); seq_printf(m, " zapped classes: %11lu\n", nr_zapped_classes); + seq_printf(m, " leaked chain hlocks: %11u\n", + nr_leaked_chain_hlocks); return 0; } -- 2.18.1
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