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Make isc_counter use atomics instead of locks

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Witold Kręcicki 2019-01-24 12:05:29 +01:00 committed by Witold Krecicki
parent 0af500a2c5
commit 42d9a536a7
1 changed files with 19 additions and 30 deletions
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49
lib/isc/counter.c
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@ -16,6 +16,7 @@
#include <stdbool.h>
#include <stddef.h>
#include <isc/atomic.h>
#include <isc/counter.h>
#include <isc/magic.h>
#include <isc/mem.h>
@ -27,10 +28,9 @@
struct isc_counter {
unsigned int magic;
isc_mem_t *mctx;
isc_mutex_t lock;
unsigned int references;
unsigned int limit;
unsigned int used;
atomic_uint_fast32_t references;
atomic_uint_fast32_t limit;
atomic_uint_fast32_t used;
};
isc_result_t
@ -43,14 +43,12 @@ isc_counter_create(isc_mem_t *mctx, int limit, isc_counter_t **counterp) {
if (counter == NULL)
return (ISC_R_NOMEMORY);
isc_mutex_init(&counter->lock);
counter->mctx = NULL;
isc_mem_attach(mctx, &counter->mctx);
counter->references = 1;
counter->limit = limit;
counter->used = 0;
atomic_store(&counter->references, 1);
atomic_store(&counter->limit, limit);
atomic_store(&counter->used, 0);
counter->magic = COUNTER_MAGIC;
*counterp = counter;
@ -61,11 +59,11 @@ isc_result_t
isc_counter_increment(isc_counter_t *counter) {
isc_result_t result = ISC_R_SUCCESS;
LOCK(&counter->lock);
counter->used++;
if (counter->limit != 0 && counter->used >= counter->limit)
uint32_t used = atomic_fetch_add(&counter->used, 1) + 1;
if (atomic_load(&counter->limit) != 0 &&
used >= atomic_load(&counter->limit)) {
result = ISC_R_QUOTA;
UNLOCK(&counter->lock);
}
return (result);
}
@ -74,16 +72,14 @@ unsigned int
isc_counter_used(isc_counter_t *counter) {
REQUIRE(VALID_COUNTER(counter));
return (counter->used);
return (atomic_load(&counter->used));
}
void
isc_counter_setlimit(isc_counter_t *counter, int limit) {
REQUIRE(VALID_COUNTER(counter));
LOCK(&counter->lock);
counter->limit = limit;
UNLOCK(&counter->lock);
atomic_store(&counter->limit, limit);
}
void
@ -91,10 +87,7 @@ isc_counter_attach(isc_counter_t *source, isc_counter_t **targetp) {
REQUIRE(VALID_COUNTER(source));
REQUIRE(targetp != NULL && *targetp == NULL);
LOCK(&source->lock);
source->references++;
INSIST(source->references > 0);
UNLOCK(&source->lock);
INSIST(atomic_fetch_add(&source->references, 1) > 0);
*targetp = source;
}
@ -102,14 +95,13 @@ isc_counter_attach(isc_counter_t *source, isc_counter_t **targetp) {
static void
destroy(isc_counter_t *counter) {
counter->magic = 0;
isc_mutex_destroy(&counter->lock);
isc_mem_putanddetach(&counter->mctx, counter, sizeof(*counter));
}
void
isc_counter_detach(isc_counter_t **counterp) {
isc_counter_t *counter;
bool want_destroy = false;
uint32_t oldrefs;
REQUIRE(counterp != NULL && *counterp != NULL);
counter = *counterp;
@ -117,13 +109,10 @@ isc_counter_detach(isc_counter_t **counterp) {
*counterp = NULL;
LOCK(&counter->lock);
INSIST(counter->references > 0);
counter->references--;
if (counter->references == 0)
want_destroy = true;
UNLOCK(&counter->lock);
oldrefs = atomic_fetch_sub(&counter->references, 1);
INSIST(oldrefs > 0);
if (want_destroy)
if (oldrefs == 1) {
destroy(counter);
}
}