qht: add qht_iter_remove
This currently has no users, but the use case is so common that I think we must support it. Note that without the appended we cannot safely remove a set of elements; a 2-step approach (i.e. qht_iter first, keep track of the to-be-deleted elements, and then a bunch of qht_remove calls) would be racy, since between the iteration and the removals other threads might insert additional elements. 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>
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@ -44,6 +44,8 @@ struct qht_stats {
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typedef bool (*qht_lookup_func_t)(const void *obj, const void *userp);
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typedef void (*qht_iter_func_t)(struct qht *ht, void *p, uint32_t h, void *up);
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typedef bool (*qht_iter_bool_func_t)(struct qht *ht, void *p, uint32_t h,
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void *up);
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#define QHT_MODE_AUTO_RESIZE 0x1 /* auto-resize when heavily loaded */
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#define QHT_MODE_RAW_MUTEXES 0x2 /* bypass the profiler (QSP) */
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@ -179,9 +181,26 @@ bool qht_resize(struct qht *ht, size_t n_elems);
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*
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* Each time it is called, user-provided @func is passed a pointer-hash pair,
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* plus @userp.
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*
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* Note: @ht cannot be accessed from @func
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* See also: qht_iter_remove()
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*/
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void qht_iter(struct qht *ht, qht_iter_func_t func, void *userp);
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/**
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* qht_iter_remove - Iterate over a QHT, optionally removing entries
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* @ht: QHT to be iterated over
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* @func: function to be called for each entry in QHT
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* @userp: additional pointer to be passed to @func
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*
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* Each time it is called, user-provided @func is passed a pointer-hash pair,
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* plus @userp. If @func returns true, the pointer-hash pair is removed.
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*
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* Note: @ht cannot be accessed from @func
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* See also: qht_iter()
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*/
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void qht_iter_remove(struct qht *ht, qht_iter_bool_func_t func, void *userp);
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/**
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* qht_statistics_init - Gather statistics from a QHT
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* @ht: QHT to gather statistics from
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74
util/qht.c
74
util/qht.c
@ -89,6 +89,19 @@
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#define QHT_BUCKET_ENTRIES 4
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#endif
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enum qht_iter_type {
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QHT_ITER_VOID, /* do nothing; use retvoid */
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QHT_ITER_RM, /* remove element if retbool returns true */
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};
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struct qht_iter {
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union {
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qht_iter_func_t retvoid;
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qht_iter_bool_func_t retbool;
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} f;
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enum qht_iter_type type;
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};
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/*
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* Do _not_ use qemu_mutex_[try]lock directly! Use these macros, otherwise
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* the profiler (QSP) will deadlock.
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@ -733,9 +746,10 @@ bool qht_remove(struct qht *ht, const void *p, uint32_t hash)
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return ret;
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}
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static inline void qht_bucket_iter(struct qht *ht, struct qht_bucket *b,
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qht_iter_func_t func, void *userp)
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static inline void qht_bucket_iter(struct qht *ht, struct qht_bucket *head,
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const struct qht_iter *iter, void *userp)
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{
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struct qht_bucket *b = head;
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int i;
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do {
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@ -743,7 +757,25 @@ static inline void qht_bucket_iter(struct qht *ht, struct qht_bucket *b,
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if (b->pointers[i] == NULL) {
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return;
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}
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func(ht, b->pointers[i], b->hashes[i], userp);
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switch (iter->type) {
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case QHT_ITER_VOID:
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iter->f.retvoid(ht, b->pointers[i], b->hashes[i], userp);
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break;
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case QHT_ITER_RM:
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if (iter->f.retbool(ht, b->pointers[i], b->hashes[i], userp)) {
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/* replace i with the last valid element in the bucket */
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seqlock_write_begin(&head->sequence);
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qht_bucket_remove_entry(b, i);
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seqlock_write_end(&head->sequence);
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qht_bucket_debug__locked(b);
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/* reevaluate i, since it just got replaced */
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i--;
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continue;
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}
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break;
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default:
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g_assert_not_reached();
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}
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}
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b = b->next;
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} while (b);
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@ -751,26 +783,48 @@ static inline void qht_bucket_iter(struct qht *ht, struct qht_bucket *b,
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/* call with all of the map's locks held */
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static inline void qht_map_iter__all_locked(struct qht *ht, struct qht_map *map,
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qht_iter_func_t func, void *userp)
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const struct qht_iter *iter,
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void *userp)
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{
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size_t i;
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for (i = 0; i < map->n_buckets; i++) {
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qht_bucket_iter(ht, &map->buckets[i], func, userp);
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qht_bucket_iter(ht, &map->buckets[i], iter, userp);
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}
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}
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void qht_iter(struct qht *ht, qht_iter_func_t func, void *userp)
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static inline void
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do_qht_iter(struct qht *ht, const struct qht_iter *iter, void *userp)
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{
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struct qht_map *map;
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map = atomic_rcu_read(&ht->map);
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qht_map_lock_buckets(map);
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/* Note: ht here is merely for carrying ht->mode; ht->map won't be read */
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qht_map_iter__all_locked(ht, map, func, userp);
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qht_map_iter__all_locked(ht, map, iter, userp);
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qht_map_unlock_buckets(map);
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}
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void qht_iter(struct qht *ht, qht_iter_func_t func, void *userp)
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{
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const struct qht_iter iter = {
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.f.retvoid = func,
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.type = QHT_ITER_VOID,
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};
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do_qht_iter(ht, &iter, userp);
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}
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void qht_iter_remove(struct qht *ht, qht_iter_bool_func_t func, void *userp)
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{
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const struct qht_iter iter = {
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.f.retbool = func,
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.type = QHT_ITER_RM,
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};
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do_qht_iter(ht, &iter, userp);
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}
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static void qht_map_copy(struct qht *ht, void *p, uint32_t hash, void *userp)
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{
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struct qht_map *new = userp;
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@ -787,6 +841,10 @@ static void qht_map_copy(struct qht *ht, void *p, uint32_t hash, void *userp)
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static void qht_do_resize_reset(struct qht *ht, struct qht_map *new, bool reset)
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{
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struct qht_map *old;
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const struct qht_iter iter = {
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.f.retvoid = qht_map_copy,
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.type = QHT_ITER_VOID,
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};
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old = ht->map;
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qht_map_lock_buckets(old);
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@ -801,7 +859,7 @@ static void qht_do_resize_reset(struct qht *ht, struct qht_map *new, bool reset)
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}
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g_assert(new->n_buckets != old->n_buckets);
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qht_map_iter__all_locked(ht, old, qht_map_copy, new);
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qht_map_iter__all_locked(ht, old, &iter, new);
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qht_map_debug__all_locked(new);
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atomic_rcu_set(&ht->map, new);
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