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qht: return existing entry when qht_insert fails

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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.henderson@linaro.org>
Reviewed-by:  Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Emilio G. Cota 2017-07-11 18:48:21 -04:00 • committed by Richard Henderson
parent 61b8cef1d4
commit 32359d529f
5 changed files with 32 additions and 16 deletions
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27
util/qht.c
View file

@ -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)