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/*
* Copyright (C) Internet Systems Consortium, Inc. ("ISC")
*
* SPDX-License-Identifier: MPL-2.0
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, you can obtain one at https://mozilla.org/MPL/2.0/.
*
* See the COPYRIGHT file distributed with this work for additional
* information regarding copyright ownership.
*/
/*! \file */
#include <stddef.h>
#include <isc/atomic.h>
#include <isc/quota.h>
#include <isc/util.h>
#define QUOTA_MAGIC ISC_MAGIC('Q', 'U', 'O', 'T')
#define VALID_QUOTA(p) ISC_MAGIC_VALID(p, QUOTA_MAGIC)
#define QUOTA_CB_MAGIC ISC_MAGIC('Q', 'T', 'C', 'B')
#define VALID_QUOTA_CB(p) ISC_MAGIC_VALID(p, QUOTA_CB_MAGIC)
void
isc_quota_init(isc_quota_t *quota, unsigned int max) {
atomic_init("a->max, max);
atomic_init("a->used, 0);
atomic_init("a->soft, 0);
atomic_init("a->waiting, 0);
ISC_LIST_INIT(quota->cbs);
isc_mutex_init("a->cblock);
ISC_LINK_INIT(quota, link);
quota->magic = QUOTA_MAGIC;
}
void
isc_quota_destroy(isc_quota_t *quota) {
REQUIRE(VALID_QUOTA(quota));
quota->magic = 0;
INSIST(atomic_load("a->used) == 0);
INSIST(atomic_load("a->waiting) == 0);
INSIST(ISC_LIST_EMPTY(quota->cbs));
atomic_store_release("a->max, 0);
atomic_store_release("a->used, 0);
atomic_store_release("a->soft, 0);
isc_mutex_destroy("a->cblock);
}
void
isc_quota_soft(isc_quota_t *quota, unsigned int soft) {
REQUIRE(VALID_QUOTA(quota));
atomic_store_release("a->soft, soft);
}
void
isc_quota_max(isc_quota_t *quota, unsigned int max) {
REQUIRE(VALID_QUOTA(quota));
atomic_store_release("a->max, max);
}
unsigned int
isc_quota_getmax(isc_quota_t *quota) {
REQUIRE(VALID_QUOTA(quota));
return (atomic_load_relaxed("a->max));
}
unsigned int
isc_quota_getsoft(isc_quota_t *quota) {
REQUIRE(VALID_QUOTA(quota));
return (atomic_load_relaxed("a->soft));
}
unsigned int
isc_quota_getused(isc_quota_t *quota) {
REQUIRE(VALID_QUOTA(quota));
return (atomic_load_relaxed("a->used));
}
static isc_result_t
quota_reserve(isc_quota_t *quota) {
isc_result_t result;
uint_fast32_t max = atomic_load_acquire("a->max);
uint_fast32_t soft = atomic_load_acquire("a->soft);
uint_fast32_t used = atomic_load_acquire("a->used);
do {
if (max != 0 && used >= max) {
return (ISC_R_QUOTA);
}
if (soft != 0 && used >= soft) {
result = ISC_R_SOFTQUOTA;
} else {
result = ISC_R_SUCCESS;
}
} while (!atomic_compare_exchange_weak_acq_rel("a->used, &used,
used + 1));
return (result);
}
/* Must be quota->cbslock locked */
static void
enqueue(isc_quota_t *quota, isc_quota_cb_t *cb) {
REQUIRE(cb != NULL);
ISC_LIST_ENQUEUE(quota->cbs, cb, link);
atomic_fetch_add_release("a->waiting, 1);
}
/* Must be quota->cbslock locked */
static isc_quota_cb_t *
dequeue(isc_quota_t *quota) {
isc_quota_cb_t *cb = ISC_LIST_HEAD(quota->cbs);
INSIST(cb != NULL);
ISC_LIST_DEQUEUE(quota->cbs, cb, link);
atomic_fetch_sub_relaxed("a->waiting, 1);
return (cb);
}
static void
quota_release(isc_quota_t *quota) {
uint_fast32_t used;
/*
* This is opportunistic - we might race with a failing quota_attach_cb
* and not detect that something is waiting, but eventually someone will
* be releasing quota and will detect it, so we don't need to worry -
* and we're saving a lot by not locking cblock every time.
*/
if (atomic_load_acquire("a->waiting) > 0) {
isc_quota_cb_t *cb = NULL;
LOCK("a->cblock);
if (atomic_load_relaxed("a->waiting) > 0) {
cb = dequeue(quota);
}
UNLOCK("a->cblock);
if (cb != NULL) {
cb->cb_func(quota, cb->data);
return;
}
}
used = atomic_fetch_sub_release("a->used, 1);
INSIST(used > 0);
}
static isc_result_t
doattach(isc_quota_t *quota, isc_quota_t **p) {
isc_result_t result;
REQUIRE(p != NULL && *p == NULL);
result = quota_reserve(quota);
if (result == ISC_R_SUCCESS || result == ISC_R_SOFTQUOTA) {
*p = quota;
}
return (result);
}
isc_result_t
isc_quota_attach(isc_quota_t *quota, isc_quota_t **quotap) {
REQUIRE(VALID_QUOTA(quota));
REQUIRE(quotap != NULL && *quotap == NULL);
return (isc_quota_attach_cb(quota, quotap, NULL));
}
isc_result_t
isc_quota_attach_cb(isc_quota_t *quota, isc_quota_t **quotap,
isc_quota_cb_t *cb) {
REQUIRE(VALID_QUOTA(quota));
REQUIRE(cb == NULL || VALID_QUOTA_CB(cb));
REQUIRE(quotap != NULL && *quotap == NULL);
isc_result_t result = doattach(quota, quotap);
if (result == ISC_R_QUOTA && cb != NULL) {
LOCK("a->cblock);
enqueue(quota, cb);
UNLOCK("a->cblock);
}
return (result);
}
void
isc_quota_cb_init(isc_quota_cb_t *cb, isc_quota_cb_func_t cb_func, void *data) {
ISC_LINK_INIT(cb, link);
cb->cb_func = cb_func;
cb->data = data;
cb->magic = QUOTA_CB_MAGIC;
}
void
isc_quota_detach(isc_quota_t **quotap) {
REQUIRE(quotap != NULL && VALID_QUOTA(*quotap));
isc_quota_t *quota = *quotap;
*quotap = NULL;
quota_release(quota);
}
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