#include <config.h>
#include <stddef.h>
#include <isc/magic.h>
#include <isc/msgs.h>
#include <isc/platform.h>
#include <isc/rwlock.h>
#include <isc/util.h>
#define RWLOCK_MAGIC ISC_MAGIC('R', 'W', 'L', 'k')
#define VALID_RWLOCK(rwl) ISC_MAGIC_VALID(rwl, RWLOCK_MAGIC)
#ifdef ISC_PLATFORM_USETHREADS
#ifndef RWLOCK_DEFAULT_READ_QUOTA
#define RWLOCK_DEFAULT_READ_QUOTA 4
#endif
#ifndef RWLOCK_DEFAULT_WRITE_QUOTA
#define RWLOCK_DEFAULT_WRITE_QUOTA 4
#endif
#ifdef ISC_RWLOCK_TRACE
#include <stdio.h>
#include <isc/thread.h>
static void
print_lock(const char *operation, isc_rwlock_t *rwl, isc_rwlocktype_t type) {
fprintf(stderr,
isc_msgcat_get(isc_msgcat, ISC_MSGSET_RWLOCK,
ISC_MSG_PRINTLOCK,
"rwlock %p thread %lu %s(%s): %s, %u active, "
"%u granted, %u rwaiting, %u wwaiting\n"),
rwl, isc_thread_self(), operation,
(type == isc_rwlocktype_read ?
isc_msgcat_get(isc_msgcat, ISC_MSGSET_RWLOCK,
ISC_MSG_READ, "read") :
isc_msgcat_get(isc_msgcat, ISC_MSGSET_RWLOCK,
ISC_MSG_WRITE, "write")),
(rwl->type == isc_rwlocktype_read ?
isc_msgcat_get(isc_msgcat, ISC_MSGSET_RWLOCK,
ISC_MSG_READING, "reading") :
isc_msgcat_get(isc_msgcat, ISC_MSGSET_RWLOCK,
ISC_MSG_WRITING, "writing")),
rwl->active, rwl->granted, rwl->readers_waiting,
rwl->writers_waiting);
}
#endif
isc_result_t
isc_rwlock_init(isc_rwlock_t *rwl, unsigned int read_quota,
unsigned int write_quota)
{
isc_result_t result;
REQUIRE(rwl != NULL);
rwl->magic = 0;
rwl->type = isc_rwlocktype_read;
rwl->active = 0;
rwl->granted = 0;
rwl->readers_waiting = 0;
rwl->writers_waiting = 0;
if (read_quota == 0)
read_quota = RWLOCK_DEFAULT_READ_QUOTA;
rwl->read_quota = read_quota;
if (write_quota == 0)
write_quota = RWLOCK_DEFAULT_WRITE_QUOTA;
rwl->write_quota = write_quota;
result = isc_mutex_init(&rwl->lock);
if (result != ISC_R_SUCCESS) {
UNEXPECTED_ERROR(__FILE__, __LINE__,
"isc_mutex_init() %s: %s",
isc_msgcat_get(isc_msgcat, ISC_MSGSET_GENERAL,
ISC_MSG_FAILED, "failed"),
isc_result_totext(result));
return (ISC_R_UNEXPECTED);
}
result = isc_condition_init(&rwl->readable);
if (result != ISC_R_SUCCESS) {
UNEXPECTED_ERROR(__FILE__, __LINE__,
"isc_condition_init(readable) %s: %s",
isc_msgcat_get(isc_msgcat, ISC_MSGSET_GENERAL,
ISC_MSG_FAILED, "failed"),
isc_result_totext(result));
return (ISC_R_UNEXPECTED);
}
result = isc_condition_init(&rwl->writeable);
if (result != ISC_R_SUCCESS) {
UNEXPECTED_ERROR(__FILE__, __LINE__,
"isc_condition_init(writeable) %s: %s",
isc_msgcat_get(isc_msgcat, ISC_MSGSET_GENERAL,
ISC_MSG_FAILED, "failed"),
isc_result_totext(result));
return (ISC_R_UNEXPECTED);
}
rwl->magic = RWLOCK_MAGIC;
return (ISC_R_SUCCESS);
}
static isc_result_t
doit(isc_rwlock_t *rwl, isc_rwlocktype_t type, isc_boolean_t nonblock) {
isc_boolean_t skip = ISC_FALSE;
isc_boolean_t done = ISC_FALSE;
isc_result_t result = ISC_R_SUCCESS;
REQUIRE(VALID_RWLOCK(rwl));
LOCK(&rwl->lock);
#ifdef ISC_RWLOCK_TRACE
print_lock(isc_msgcat_get(isc_msgcat, ISC_MSGSET_RWLOCK,
ISC_MSG_PRELOCK, "prelock"), rwl, type);
#endif
if (type == isc_rwlocktype_read) {
if (rwl->readers_waiting != 0)
skip = ISC_TRUE;
while (!done) {
if (!skip &&
((rwl->active == 0 ||
(rwl->type == isc_rwlocktype_read &&
(rwl->writers_waiting == 0 ||
rwl->granted < rwl->read_quota)))))
{
rwl->type = isc_rwlocktype_read;
rwl->active++;
rwl->granted++;
done = ISC_TRUE;
} else if (nonblock) {
result = ISC_R_LOCKBUSY;
done = ISC_TRUE;
} else {
skip = ISC_FALSE;
rwl->readers_waiting++;
WAIT(&rwl->readable, &rwl->lock);
rwl->readers_waiting--;
}
}
} else {
if (rwl->writers_waiting != 0)
skip = ISC_TRUE;
while (!done) {
if (!skip && rwl->active == 0) {
rwl->type = isc_rwlocktype_write;
rwl->active = 1;
rwl->granted++;
done = ISC_TRUE;
} else if (nonblock) {
result = ISC_R_LOCKBUSY;
done = ISC_TRUE;
} else {
skip = ISC_FALSE;
rwl->writers_waiting++;
WAIT(&rwl->writeable, &rwl->lock);
rwl->writers_waiting--;
}
}
}
#ifdef ISC_RWLOCK_TRACE
print_lock(isc_msgcat_get(isc_msgcat, ISC_MSGSET_RWLOCK,
ISC_MSG_POSTLOCK, "postlock"), rwl, type);
#endif
UNLOCK(&rwl->lock);
return (result);
}
isc_result_t
isc_rwlock_lock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
return (doit(rwl, type, ISC_FALSE));
}
isc_result_t
isc_rwlock_trylock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
return (doit(rwl, type, ISC_TRUE));
}
isc_result_t
isc_rwlock_unlock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
REQUIRE(VALID_RWLOCK(rwl));
LOCK(&rwl->lock);
REQUIRE(rwl->type == type);
UNUSED(type);
#ifdef ISC_RWLOCK_TRACE
print_lock(isc_msgcat_get(isc_msgcat, ISC_MSGSET_RWLOCK,
ISC_MSG_PREUNLOCK, "preunlock"), rwl, type);
#endif
INSIST(rwl->active > 0);
rwl->active--;
if (rwl->active == 0) {
if (rwl->type == isc_rwlocktype_read) {
rwl->granted = 0;
if (rwl->writers_waiting > 0) {
rwl->type = isc_rwlocktype_write;
SIGNAL(&rwl->writeable);
} else if (rwl->readers_waiting > 0) {
BROADCAST(&rwl->readable);
}
} else {
if (rwl->readers_waiting > 0) {
if (rwl->writers_waiting > 0 &&
rwl->granted < rwl->write_quota) {
SIGNAL(&rwl->writeable);
} else {
rwl->granted = 0;
rwl->type = isc_rwlocktype_read;
BROADCAST(&rwl->readable);
}
} else if (rwl->writers_waiting > 0) {
rwl->granted = 0;
SIGNAL(&rwl->writeable);
} else {
rwl->granted = 0;
}
}
}
#ifdef ISC_RWLOCK_TRACE
print_lock(isc_msgcat_get(isc_msgcat, ISC_MSGSET_RWLOCK,
ISC_MSG_POSTUNLOCK, "postunlock"),
rwl, type);
#endif
UNLOCK(&rwl->lock);
return (ISC_R_SUCCESS);
}
void
isc_rwlock_destroy(isc_rwlock_t *rwl) {
REQUIRE(VALID_RWLOCK(rwl));
LOCK(&rwl->lock);
REQUIRE(rwl->active == 0 &&
rwl->readers_waiting == 0 &&
rwl->writers_waiting == 0);
UNLOCK(&rwl->lock);
rwl->magic = 0;
(void)isc_condition_destroy(&rwl->readable);
(void)isc_condition_destroy(&rwl->writeable);
DESTROYLOCK(&rwl->lock);
}
#else
isc_result_t
isc_rwlock_init(isc_rwlock_t *rwl, unsigned int read_quota,
unsigned int write_quota)
{
REQUIRE(rwl != NULL);
UNUSED(read_quota);
UNUSED(write_quota);
rwl->type = isc_rwlocktype_read;
rwl->active = 0;
rwl->magic = RWLOCK_MAGIC;
return (ISC_R_SUCCESS);
}
isc_result_t
isc_rwlock_lock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
REQUIRE(VALID_RWLOCK(rwl));
if (type == isc_rwlocktype_read) {
if (rwl->type != isc_rwlocktype_read && rwl->active != 0)
return (ISC_R_LOCKBUSY);
rwl->type = isc_rwlocktype_read;
rwl->active++;
} else {
if (rwl->active != 0)
return (ISC_R_LOCKBUSY);
rwl->type = isc_rwlocktype_write;
rwl->active = 1;
}
return (ISC_R_SUCCESS);
}
isc_result_t
isc_rwlock_trylock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
return (isc_rwlock_lock(rwl, type));
}
isc_result_t
isc_rwlock_unlock(isc_rwlock_t *rwl, isc_rwlocktype_t type) {
REQUIRE(VALID_RWLOCK(rwl));
REQUIRE(rwl->type == type);
UNUSED(type);
INSIST(rwl->active > 0);
rwl->active--;
return (ISC_R_SUCCESS);
}
void
isc_rwlock_destroy(isc_rwlock_t *rwl) {
REQUIRE(rwl != NULL);
REQUIRE(rwl->active == 0);
rwl->magic = 0;
}
#endif