diff options
Diffstat (limited to 'kernel/trace/tracing_map.c')
| -rw-r--r-- | kernel/trace/tracing_map.c | 41 |
1 files changed, 36 insertions, 5 deletions
diff --git a/kernel/trace/tracing_map.c b/kernel/trace/tracing_map.c index 07e75344725b..b30f3439f27f 100644 --- a/kernel/trace/tracing_map.c +++ b/kernel/trace/tracing_map.c @@ -414,7 +414,9 @@ static inline struct tracing_map_elt * __tracing_map_insert(struct tracing_map *map, void *key, bool lookup_only) { u32 idx, key_hash, test_key; + int dup_try = 0; struct tracing_map_entry *entry; + struct tracing_map_elt *val; key_hash = jhash(key, map->key_size, 0); if (key_hash == 0) @@ -426,11 +428,33 @@ __tracing_map_insert(struct tracing_map *map, void *key, bool lookup_only) entry = TRACING_MAP_ENTRY(map->map, idx); test_key = entry->key; - if (test_key && test_key == key_hash && entry->val && - keys_match(key, entry->val->key, map->key_size)) { - if (!lookup_only) - atomic64_inc(&map->hits); - return entry->val; + if (test_key && test_key == key_hash) { + val = READ_ONCE(entry->val); + if (val && + keys_match(key, val->key, map->key_size)) { + if (!lookup_only) + atomic64_inc(&map->hits); + return val; + } else if (unlikely(!val)) { + /* + * The key is present. But, val (pointer to elt + * struct) is still NULL. which means some other + * thread is in the process of inserting an + * element. + * + * On top of that, it's key_hash is same as the + * one being inserted right now. So, it's + * possible that the element has the same + * key as well. + */ + + dup_try++; + if (dup_try > map->map_size) { + atomic64_inc(&map->drops); + break; + } + continue; + } } if (!test_key) { @@ -452,6 +476,13 @@ __tracing_map_insert(struct tracing_map *map, void *key, bool lookup_only) atomic64_inc(&map->hits); return entry->val; + } else { + /* + * cmpxchg() failed. Loop around once + * more to check what key was inserted. + */ + dup_try++; + continue; } } |