diff options
| -rw-r--r-- | include/qemu/qht.h | 5 | ||||
| -rw-r--r-- | util/qht.c | 7 |
2 files changed, 11 insertions, 1 deletions
diff --git a/include/qemu/qht.h b/include/qemu/qht.h index 70bfc68b8d..311139b85a 100644 --- a/include/qemu/qht.h +++ b/include/qemu/qht.h @@ -69,6 +69,9 @@ void qht_destroy(struct qht *ht); * Attempting to insert a NULL @p is a bug. * Inserting the same pointer @p with different @hash values is a bug. * + * In case of successful operation, smp_wmb() is implied before the pointer is + * inserted into the hash table. + * * Returns true on sucess. * Returns false if the @p-@hash pair already exists in the hash table. */ @@ -83,6 +86,8 @@ bool qht_insert(struct qht *ht, void *p, uint32_t hash); * * Needs to be called under an RCU read-critical section. * + * smp_read_barrier_depends() is implied before the call to @func. + * * The user-provided @func compares pointers in QHT against @userp. * If the function returns true, a match has been found. * diff --git a/util/qht.c b/util/qht.c index 40d6e218f7..28ce289245 100644 --- a/util/qht.c +++ b/util/qht.c @@ -445,7 +445,11 @@ void *qht_do_lookup(struct qht_bucket *head, qht_lookup_func_t func, do { for (i = 0; i < QHT_BUCKET_ENTRIES; i++) { if (b->hashes[i] == hash) { - void *p = atomic_read(&b->pointers[i]); + /* The pointer is dereferenced before seqlock_read_retry, + * so (unlike qht_insert__locked) we need to use + * atomic_rcu_read here. + */ + void *p = atomic_rcu_read(&b->pointers[i]); if (likely(p) && likely(func(p, userp))) { return p; @@ -535,6 +539,7 @@ static bool qht_insert__locked(struct qht *ht, struct qht_map *map, atomic_rcu_set(&prev->next, b); } b->hashes[i] = hash; + /* smp_wmb() implicit in seqlock_write_begin. */ atomic_set(&b->pointers[i], p); seqlock_write_end(&head->sequence); return true; |