Emilio G. Cota <c...@braap.org> writes:
> The meaning of "existing" is now changed to "matches in hash and
> ht->cmp result". This is saner than just checking the pointer value.
>
> Suggested-by: Richard Henderson <richard.hender...@linaro.org>
> Reviewed-by: Richard Henderson <richard.hender...@linaro.org>
> Signed-off-by: Emilio G. Cota <c...@braap.org>
Reviewed-by: Alex Bennée <alex.ben...@linaro.org>
> ---
> include/qemu/qht.h | 7 +++++--
> accel/tcg/translate-all.c | 2 +-
> tests/qht-bench.c | 4 ++--
> tests/test-qht.c | 8 +++++++-
> util/qht.c | 27 +++++++++++++++++----------
> 5 files changed, 32 insertions(+), 16 deletions(-)
>
> diff --git a/include/qemu/qht.h b/include/qemu/qht.h
> index 5f03a0f..1fb9116 100644
> --- a/include/qemu/qht.h
> +++ b/include/qemu/qht.h
> @@ -70,6 +70,7 @@ void qht_destroy(struct qht *ht);
> * @ht: QHT to insert to
> * @p: pointer to be inserted
> * @hash: hash corresponding to @p
> + * @existing: address where the pointer to an existing entry can be copied to
> *
> * Attempting to insert a NULL @p is a bug.
> * Inserting the same pointer @p with different @hash values is a bug.
> @@ -78,9 +79,11 @@ void qht_destroy(struct qht *ht);
> * inserted into the hash table.
> *
> * Returns true on success.
> - * Returns false if the @p-@hash pair already exists in the hash table.
> + * Returns false if there is an existing entry in the table that is
> equivalent
> + * (i.e. ht->cmp matches and the hash is the same) to @p-@h. If @existing
> + * is !NULL, a pointer to this existing entry is copied to it.
> */
> -bool qht_insert(struct qht *ht, void *p, uint32_t hash);
> +bool qht_insert(struct qht *ht, void *p, uint32_t hash, void **existing);
>
> /**
> * qht_lookup_custom - Look up a pointer using a custom comparison function.
> diff --git a/accel/tcg/translate-all.c b/accel/tcg/translate-all.c
> index 5b7b91d..8080eb7 100644
> --- a/accel/tcg/translate-all.c
> +++ b/accel/tcg/translate-all.c
> @@ -1242,7 +1242,7 @@ static void tb_link_page(TranslationBlock *tb,
> tb_page_addr_t phys_pc,
> /* add in the hash table */
> h = tb_hash_func(phys_pc, tb->pc, tb->flags, tb->cflags & CF_HASH_MASK,
> tb->trace_vcpu_dstate);
> - qht_insert(&tb_ctx.htable, tb, h);
> + qht_insert(&tb_ctx.htable, tb, h, NULL);
>
> #ifdef CONFIG_USER_ONLY
> if (DEBUG_TB_CHECK_GATE) {
> diff --git a/tests/qht-bench.c b/tests/qht-bench.c
> index c94ac25..f492b3a 100644
> --- a/tests/qht-bench.c
> +++ b/tests/qht-bench.c
> @@ -163,7 +163,7 @@ static void do_rw(struct thread_info *info)
> bool written = false;
>
> if (qht_lookup(&ht, p, hash) == NULL) {
> - written = qht_insert(&ht, p, hash);
> + written = qht_insert(&ht, p, hash, NULL);
> }
> if (written) {
> stats->in++;
> @@ -322,7 +322,7 @@ static void htable_init(void)
> r = xorshift64star(r);
> p = &keys[r & (init_range - 1)];
> hash = h(*p);
> - if (qht_insert(&ht, p, hash)) {
> + if (qht_insert(&ht, p, hash, NULL)) {
> break;
> }
> retries++;
> diff --git a/tests/test-qht.c b/tests/test-qht.c
> index b069881..dda6a06 100644
> --- a/tests/test-qht.c
> +++ b/tests/test-qht.c
> @@ -27,11 +27,17 @@ static void insert(int a, int b)
>
> for (i = a; i < b; i++) {
> uint32_t hash;
> + void *existing;
> + bool inserted;
>
> arr[i] = i;
> hash = i;
>
> - qht_insert(&ht, &arr[i], hash);
> + inserted = qht_insert(&ht, &arr[i], hash, NULL);
> + g_assert_true(inserted);
> + inserted = qht_insert(&ht, &arr[i], hash, &existing);
> + g_assert_false(inserted);
> + g_assert_true(existing == &arr[i]);
> }
> }
>
> diff --git a/util/qht.c b/util/qht.c
> index 8610ce3..9d030e7 100644
> --- a/util/qht.c
> +++ b/util/qht.c
> @@ -511,9 +511,9 @@ void *qht_lookup(struct qht *ht, const void *userp,
> uint32_t hash)
> }
>
> /* call with head->lock held */
> -static bool qht_insert__locked(struct qht *ht, struct qht_map *map,
> - struct qht_bucket *head, void *p, uint32_t
> hash,
> - bool *needs_resize)
> +static void *qht_insert__locked(struct qht *ht, struct qht_map *map,
> + struct qht_bucket *head, void *p, uint32_t
> hash,
> + bool *needs_resize)
> {
> struct qht_bucket *b = head;
> struct qht_bucket *prev = NULL;
> @@ -523,8 +523,9 @@ static bool qht_insert__locked(struct qht *ht, struct
> qht_map *map,
> do {
> for (i = 0; i < QHT_BUCKET_ENTRIES; i++) {
> if (b->pointers[i]) {
> - if (unlikely(b->pointers[i] == p)) {
> - return false;
> + if (unlikely(b->hashes[i] == hash &&
> + ht->cmp(b->pointers[i], p))) {
> + return b->pointers[i];
> }
> } else {
> goto found;
> @@ -553,7 +554,7 @@ static bool qht_insert__locked(struct qht *ht, struct
> qht_map *map,
> atomic_set(&b->hashes[i], hash);
> atomic_set(&b->pointers[i], p);
> seqlock_write_end(&head->sequence);
> - return true;
> + return NULL;
> }
>
> static __attribute__((noinline)) void qht_grow_maybe(struct qht *ht)
> @@ -577,25 +578,31 @@ static __attribute__((noinline)) void
> qht_grow_maybe(struct qht *ht)
> qemu_mutex_unlock(&ht->lock);
> }
>
> -bool qht_insert(struct qht *ht, void *p, uint32_t hash)
> +bool qht_insert(struct qht *ht, void *p, uint32_t hash, void **existing)
> {
> struct qht_bucket *b;
> struct qht_map *map;
> bool needs_resize = false;
> - bool ret;
> + void *prev;
>
> /* NULL pointers are not supported */
> qht_debug_assert(p);
>
> b = qht_bucket_lock__no_stale(ht, hash, &map);
> - ret = qht_insert__locked(ht, map, b, p, hash, &needs_resize);
> + prev = qht_insert__locked(ht, map, b, p, hash, &needs_resize);
> qht_bucket_debug__locked(b);
> qemu_spin_unlock(&b->lock);
>
> if (unlikely(needs_resize) && ht->mode & QHT_MODE_AUTO_RESIZE) {
> qht_grow_maybe(ht);
> }
> - return ret;
> + if (likely(prev == NULL)) {
> + return true;
> + }
> + if (existing) {
> + *existing = prev;
> + }
> + return false;
> }
>
> static inline bool qht_entry_is_last(struct qht_bucket *b, int pos)
--
Alex Bennée
