Messages in this thread Patch in this message |  | | Date | Tue, 4 Feb 2020 13:36:29 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH v5 6/7] locking/lockdep: Reuse freed chain_hlocks entries |
| |
On Mon, Feb 03, 2020 at 11:41:46AM -0500, Waiman Long wrote: > + if (unlikely(size < 2)) > + return; // XXX leak!
Stuck this on top...
--- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -2631,7 +2631,8 @@ struct lock_chain lock_chains[MAX_LOCKDE static DECLARE_BITMAP(lock_chains_in_use, MAX_LOCKDEP_CHAINS); static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS]; unsigned long nr_zapped_lock_chains; -unsigned int nr_free_chain_hlocks; /* Free cfhain_hlocks in buckets */ +unsigned int nr_free_chain_hlocks; /* Free chain_hlocks in buckets */ +unsigned int nr_lost_chain_hlocks; /* Lost chain_hlocks */ unsigned int nr_large_chain_blocks; /* size > MAX_CHAIN_BUCKETS */ /* @@ -2718,8 +2719,17 @@ static inline void add_chain_block(int o int bucket = size_to_bucket(size); int next = chain_block_buckets[bucket]; - if (unlikely(size < 2)) - return; // XXX leak! + if (unlikely(size < 2)) { + /* + * We can't store single entries on the freelist. Leak them. + * + * One possible way out would be to uniquely mark them, other + * than with CHAIN_BLK_FLAG, such that we can recover them when + * the block before it is re-added. + */ + nr_lost_chain_hlocks++; + return; + } init_chain_block(offset, next, bucket, size); chain_block_buckets[bucket] = offset; @@ -2798,8 +2808,8 @@ static int alloc_chain_hlocks(int req) search: /* - * linear search in the 'dump' bucket; look for an exact match or the - * largest block. + * linear search of the variable sized freelist; look for an exact + * match or the largest block. */ for_each_chain_block(0, prev, curr, next) { size = chain_block_size(curr); --- a/kernel/locking/lockdep_internals.h +++ b/kernel/locking/lockdep_internals.h @@ -141,6 +141,7 @@ extern unsigned int nr_hardirq_chains; extern unsigned int nr_softirq_chains; extern unsigned int nr_process_chains; extern unsigned int nr_free_chain_hlocks; +extern unsigned int nr_lost_chain_hlocks; extern unsigned int nr_large_chain_blocks; extern unsigned int max_lockdep_depth; --- a/kernel/locking/lockdep_proc.c +++ b/kernel/locking/lockdep_proc.c @@ -278,9 +278,11 @@ static int lockdep_stats_show(struct seq #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: %11lu [max: %lu]\n", - MAX_LOCKDEP_CHAIN_HLOCKS - nr_free_chain_hlocks, + seq_printf(m, " dependency chain hlocks used: %11lu [max: %lu]\n", + MAX_LOCKDEP_CHAIN_HLOCKS - (nr_free_chain_hlocks - nr_lost_chain_hlocks), MAX_LOCKDEP_CHAIN_HLOCKS); + seq_printf(m, " dependency chain hlocks free: %11lu\n", nr_free_chain_hlocks); + seq_printf(m, " dependency chain hlocks lost: %11lu\n", nr_lost_chain_hlocks); #endif #ifdef CONFIG_TRACE_IRQFLAGS
|  |