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Remove isc_rwlock_downgrade() from isc_rwlock

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The isc_rwlock_downgrade() is not used anywhere, so we can remove it and
make the pthread_rwlock implementation simpler.
This commit is contained in:
Ondřej Surý 2022-10-14 11:42:31 +02:00
parent 1d448de802
commit 98b7a93772
No known key found for this signature in database
GPG key ID: 2820F37E873DEA41
2 changed files with 11 additions and 100 deletions
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25
lib/isc/include/isc/rwlock.h
View file

@ -35,15 +35,10 @@ typedef enum {
#if USE_PTHREAD_RWLOCK
#include <pthread.h>
struct isc_rwlock {
pthread_rwlock_t rwlock;
atomic_bool downgrade;
};
#if ISC_TRACK_PTHREADS_OBJECTS
typedef struct isc_rwlock *isc_rwlock_t;
typedef struct isc_rwlock isc__rwlock_t;
typedef pthread_rwlock_t *isc_rwlock_t;
typedef pthread_rwlock_t isc__rwlock_t;
#define isc_rwlock_init(rwl, rq, wq) \
{ \
@ -54,7 +49,6 @@ typedef struct isc_rwlock isc__rwlock_t;
#define isc_rwlock_trylock(rwl, type) isc___rwlock_trylock(*rwl, type)
#define isc_rwlock_unlock(rwl, type) isc__rwlock_unlock(*rwl, type)
#define isc_rwlock_tryupgrade(rwl) isc___rwlock_tryupgrade(*rwl)
#define isc_rwlock_downgrade(rwl) isc__rwlock_downgrade(*rwl)
#define isc_rwlock_destroy(rwl) \
{ \
isc___rwlock_destroy(*rwl); \
@ -63,15 +57,14 @@ typedef struct isc_rwlock isc__rwlock_t;
#else /* ISC_TRACK_PTHREADS_OBJECTS */
typedef struct isc_rwlock isc_rwlock_t;
typedef struct isc_rwlock isc__rwlock_t;
typedef pthread_rwlock_t isc_rwlock_t;
typedef pthread_rwlock_t isc__rwlock_t;
#define isc_rwlock_init(rwl, rq, wq) isc__rwlock_init(rwl, rq, wq)
#define isc_rwlock_lock(rwl, type) isc__rwlock_lock(rwl, type)
#define isc_rwlock_trylock(rwl, type) isc___rwlock_trylock(rwl, type)
#define isc_rwlock_unlock(rwl, type) isc__rwlock_unlock(rwl, type)
#define isc_rwlock_tryupgrade(rwl) isc___rwlock_tryupgrade(rwl)
#define isc_rwlock_downgrade(rwl) isc__rwlock_downgrade(rwl)
#define isc_rwlock_destroy(rwl) isc__rwlock_destroy(rwl)
#endif /* ISC_TRACK_PTHREADS_OBJECTS */
@ -122,7 +115,6 @@ typedef struct isc_rwlock isc__rwlock_t;
#define isc_rwlock_trylock(rwl, type) isc___rwlock_trylock(rwl, type)
#define isc_rwlock_unlock(rwl, type) isc__rwlock_unlock(rwl, type)
#define isc_rwlock_tryupgrade(rwl) isc___rwlock_tryupgrade(rwl)
#define isc_rwlock_downgrade(rwl) isc__rwlock_downgrade(rwl)
#define isc_rwlock_destroy(rwl) isc__rwlock_destroy(rwl)
#endif /* USE_PTHREAD_RWLOCK */
@ -145,12 +137,6 @@ typedef struct isc_rwlock isc__rwlock_t;
PTHREADS_RUNTIME_CHECK(isc___rwlock_unlock, _ret); \
}
#define isc__rwlock_downgrade(rwl) \
{ \
int _ret = isc___rwlock_downgrade(rwl); \
PTHREADS_RUNTIME_CHECK(isc___rwlock_downgrade, _ret); \
}
#define isc__rwlock_destroy(rwl) \
{ \
int _ret = isc___rwlock_destroy(rwl); \
@ -173,9 +159,6 @@ isc___rwlock_unlock(isc__rwlock_t *rwl, isc_rwlocktype_t type);
isc_result_t
isc___rwlock_tryupgrade(isc__rwlock_t *rwl);
int
isc___rwlock_downgrade(isc__rwlock_t *rwl);
int
isc___rwlock_destroy(isc__rwlock_t *rwl);

86
lib/isc/rwlock.c
View file

@ -39,39 +39,18 @@ isc___rwlock_init(isc__rwlock_t *rwl, unsigned int read_quota,
UNUSED(read_quota);
UNUSED(write_quota);
ret = pthread_rwlock_init(&rwl->rwlock, NULL);
atomic_init(&rwl->downgrade, false);
ret = pthread_rwlock_init(rwl, NULL);
return (ret);
}
int
isc___rwlock_lock(isc__rwlock_t *rwl, isc_rwlocktype_t type) {
int ret;
switch (type) {
case isc_rwlocktype_read:
return (pthread_rwlock_rdlock(&rwl->rwlock));
return (pthread_rwlock_rdlock(rwl));
case isc_rwlocktype_write:
while (true) {
ret = pthread_rwlock_wrlock(&rwl->rwlock);
if (ret != 0) {
return (ret);
}
/* Unlock if in middle of downgrade operation */
if (atomic_load_acquire(&rwl->downgrade)) {
ret = pthread_rwlock_unlock(&rwl->rwlock);
if (ret != 0) {
return (ret);
}
while (atomic_load_acquire(&rwl->downgrade)) {
}
continue;
}
break;
}
return (0);
return (pthread_rwlock_wrlock(rwl));
default:
UNREACHABLE();
}
@ -82,14 +61,10 @@ isc___rwlock_trylock(isc__rwlock_t *rwl, isc_rwlocktype_t type) {
int ret = 0;
switch (type) {
case isc_rwlocktype_read:
ret = pthread_rwlock_tryrdlock(&rwl->rwlock);
ret = pthread_rwlock_tryrdlock(rwl);
break;
case isc_rwlocktype_write:
ret = pthread_rwlock_trywrlock(&rwl->rwlock);
if ((ret == 0) && atomic_load_acquire(&rwl->downgrade)) {
RUNTIME_CHECK(pthread_rwlock_unlock(&rwl->rwlock) == 0);
return (ISC_R_LOCKBUSY);
}
ret = pthread_rwlock_trywrlock(rwl);
break;
default:
UNREACHABLE();
@ -110,7 +85,7 @@ isc___rwlock_trylock(isc__rwlock_t *rwl, isc_rwlocktype_t type) {
int
isc___rwlock_unlock(isc__rwlock_t *rwl, isc_rwlocktype_t type) {
UNUSED(type);
return (pthread_rwlock_unlock(&rwl->rwlock));
return (pthread_rwlock_unlock(rwl));
}
isc_result_t
@ -119,30 +94,9 @@ isc___rwlock_tryupgrade(isc__rwlock_t *rwl) {
return (ISC_R_LOCKBUSY);
}
int
isc___rwlock_downgrade(isc__rwlock_t *rwl) {
int ret;
atomic_store_release(&rwl->downgrade, true);
ret = pthread_rwlock_unlock(&rwl->rwlock);
if (ret != 0) {
return (ret);
}
ret = pthread_rwlock_rdlock(&rwl->rwlock);
if (ret != 0) {
return (ret);
}
atomic_store_release(&rwl->downgrade, false);
return (0);
}
int
isc___rwlock_destroy(isc__rwlock_t *rwl) {
return (pthread_rwlock_destroy(&rwl->rwlock));
return (pthread_rwlock_destroy(rwl));
}
#else /* if USE_PTHREAD_RWLOCK */
@ -555,32 +509,6 @@ isc___rwlock_tryupgrade(isc__rwlock_t *rwl) {
return (ISC_R_SUCCESS);
}
int
isc___rwlock_downgrade(isc__rwlock_t *rwl) {
int32_t prev_readers;
REQUIRE(VALID_RWLOCK(rwl));
/* Become an active reader. */
prev_readers = atomic_fetch_add_release(&rwl->cnt_and_flag,
READER_INCR);
/* We must have been a writer. */
INSIST((prev_readers & WRITER_ACTIVE) != 0);
/* Complete write */
atomic_fetch_sub_release(&rwl->cnt_and_flag, WRITER_ACTIVE);
atomic_fetch_add_release(&rwl->write_completions, 1);
/* Resume other readers */
LOCK(&rwl->lock);
if (rwl->readers_waiting > 0) {
BROADCAST(&rwl->readable);
}
UNLOCK(&rwl->lock);
return (0);
}
int
isc___rwlock_unlock(isc__rwlock_t *rwl, isc_rwlocktype_t type) {
int32_t prev_cnt;