void
test_sub ()
{
v = res = 20;
count = 0;
atomic_fetch_sub (&v, count + 1);
if (v != --res)
abort ();
atomic_fetch_sub_explicit (&v, count + 1, memory_order_consume);
if (v != --res)
abort ();
atomic_fetch_sub (&v, 1);
if (v != --res)
abort ();
atomic_fetch_sub_explicit (&v, 1, memory_order_release);
if (v != --res)
abort ();
atomic_fetch_sub (&v, count + 1);
if (v != --res)
abort ();
atomic_fetch_sub_explicit (&v, count + 1, memory_order_seq_cst);
if (v != --res)
abort ();
}
static inline void write_lock(rwlock_t *rw)
{
int priorvalue = atomic_fetch_sub_explicit(&rw->lock, RW_LOCK_BIAS, memory_order_acquire);
while (priorvalue != RW_LOCK_BIAS) {
atomic_fetch_add_explicit(&rw->lock, RW_LOCK_BIAS, memory_order_relaxed);
do {
priorvalue = atomic_load_explicit(&rw->lock, memory_order_relaxed);
} while (priorvalue != RW_LOCK_BIAS);
priorvalue = atomic_fetch_sub_explicit(&rw->lock, RW_LOCK_BIAS, memory_order_acquire);
}
}
static inline void read_lock(rwlock_t *rw)
{
int priorvalue = atomic_fetch_sub_explicit(&rw->lock, 1, memory_order_acquire);
while (priorvalue <= 0) {
atomic_fetch_add_explicit(&rw->lock, 1, memory_order_relaxed);
do {
priorvalue = atomic_load_explicit(&rw->lock, memory_order_relaxed);
} while (priorvalue <= 0);
priorvalue = atomic_fetch_sub_explicit(&rw->lock, 1, memory_order_acquire);
}
}
/** Initialize DALEC. MPI must be initialized before this can be called. It
* invalid to make DALEC calls before initialization. Collective on the world
* group.
*
* @return Zero on success
*/
int PDALEC_Initialize(MPI_Comm user_comm)
{
int dalec_alive = atomic_fetch_sub_explicit(&(DALECI_GLOBAL_STATE.alive),
1,memory_order_seq_cst);
if (dalec_alive == 0) {
/* Initialize, since this is the first call to this function. */
int mpi_is_init, mpi_is_fin;
MPI_Initialized(&mpi_is_init);
MPI_Finalized(&mpi_is_fin);
if (!mpi_is_init || mpi_is_fin) {
DALECI_Warning("MPI must be active when calling DALEC_Initialize");
return DALEC_ERROR_MPI_USAGE;
}
/* Always dupe the user communicator for internal usage. */
/* Do not abort on MPI failure, let user handle if MPI does not abort. */
int rc = MPI_Comm_dup(user_comm, &DALECI_GLOBAL_STATE.mpi_comm);
return DALECI_Check_MPI("DALEC_Initialize", "MPI_Comm_dup", rc);
/* Determine what level of threading MPI supports. */
int mpi_thread_level;
MPI_Query_thread(&mpi_thread_level);
DALECI_GLOBAL_STATE.mpi_thread_level;
} else {
/* Library has already been initialized. */
return DALEC_SUCCESS;
}
}
static void mainloopDataNotifyDecrease(void *p) {
caerMainloopData mainloopData = p;
// No special memory order for decrease, because the acquire load to even start running
// through a mainloop already synchronizes with the release store above.
atomic_fetch_sub_explicit(&mainloopData->dataAvailable, 1, memory_order_relaxed);
}
static inline int write_trylock(rwlock_t *rw)
{
int priorvalue = atomic_fetch_sub_explicit(&rw->lock, RW_LOCK_BIAS, memory_order_acquire);
if (priorvalue == RW_LOCK_BIAS)
return 1;
atomic_fetch_add_explicit(&rw->lock, RW_LOCK_BIAS, memory_order_relaxed);
return 0;
}
static inline int read_trylock(rwlock_t *rw)
{
int priorvalue = atomic_fetch_sub_explicit(&rw->lock, 1, memory_order_acquire);
if (priorvalue > 0)
return 1;
atomic_fetch_add_explicit(&rw->lock, 1, memory_order_relaxed);
return 0;
}
void
test_fetch_sub ()
{
v = res = 20;
count = 0;
if (atomic_fetch_sub_explicit (&v, count + 1, memory_order_relaxed) != res--)
abort ();
if (atomic_fetch_sub_explicit (&v, 1, memory_order_consume) != res--)
abort ();
if (atomic_fetch_sub_explicit (&v, count + 1, memory_order_acquire) != res--)
abort ();
if (atomic_fetch_sub_explicit (&v, 1, memory_order_release) != res--)
abort ();
if (atomic_fetch_sub_explicit (&v, count + 1, memory_order_acq_rel) != res--)
abort ();
if (atomic_fetch_sub_explicit (&v, 1, memory_order_seq_cst) != res--)
abort ();
if (atomic_fetch_sub (&v, 1) != res--)
abort ();
}
int pthread_mutex_unlock(pthread_mutex_t* mutex_interface) {
#if !defined(__LP64__)
// Some apps depend on being able to pass NULL as a mutex and get EINVAL
// back. Don't need to worry about it for LP64 since the ABI is brand new,
// but keep compatibility for LP32. http://b/19995172.
if (mutex_interface == NULL) {
return EINVAL;
}
#endif
pthread_mutex_internal_t* mutex = __get_internal_mutex(mutex_interface);
uint16_t old_state = atomic_load_explicit(&mutex->state, memory_order_relaxed);
uint16_t mtype = (old_state & MUTEX_TYPE_MASK);
uint16_t shared = (old_state & MUTEX_SHARED_MASK);
// Handle common case first.
if (__predict_true(mtype == MUTEX_TYPE_BITS_NORMAL)) {
__pthread_normal_mutex_unlock(mutex, shared);
return 0;
}
// Do we already own this recursive or error-check mutex?
pid_t tid = __get_thread()->tid;
if ( tid != atomic_load_explicit(&mutex->owner_tid, memory_order_relaxed) ) {
return EPERM;
}
// If the counter is > 0, we can simply decrement it atomically.
// Since other threads can mutate the lower state bits (and only the
// lower state bits), use a compare_exchange loop to do it.
if (!MUTEX_COUNTER_BITS_IS_ZERO(old_state)) {
// We still own the mutex, so a release fence is not needed.
atomic_fetch_sub_explicit(&mutex->state, MUTEX_COUNTER_BITS_ONE, memory_order_relaxed);
return 0;
}
// The counter is 0, so we'are going to unlock the mutex by resetting its
// state to unlocked, we need to perform a atomic_exchange inorder to read
// the current state, which will be locked_contended if there may have waiters
// to awake.
// A release fence is required to make previous stores visible to next
// lock owner threads.
atomic_store_explicit(&mutex->owner_tid, 0, memory_order_relaxed);
const uint16_t unlocked = mtype | shared | MUTEX_STATE_BITS_UNLOCKED;
old_state = atomic_exchange_explicit(&mutex->state, unlocked, memory_order_release);
if (MUTEX_STATE_BITS_IS_LOCKED_CONTENDED(old_state)) {
__futex_wake_ex(&mutex->state, shared, 1);
}
return 0;
}
void reader(int id)
{
for (;;) {
int idx = atomic_fetch_sub_explicit(&cnt, 1, std::memory_order_relaxed);
if (idx >= 0) {
std::cout << "reader " << std::to_string(id) << " processed item "
<< std::to_string(data[idx]) << '\n';
} else {
std::cout << "reader " << std::to_string(id) << " done\n";
break;
}
}
}
void LSQBaseRelease(LSQBaseTypeRef self)
{
atomic_fetch_sub_explicit(&self->data.refcount, 1, memory_order_release);
// Execute release callback
if (self->vtable != NULL && self->vtable->release != NULL)
{
self->vtable->release(self->data.userdata);
}
// Execute deallock
if (self->data.refcount <= 0)
{
LSQBaseDealloc(self);
}
}
void tm_thread_do_exit(void)
{
assert(current_thread->held_locks == 0);
assert(current_thread->blocklist == 0);
struct async_call *thread_cleanup_call = async_call_create(¤t_thread->cleanup_call, 0,
tm_thread_destroy, (unsigned long)current_thread, 0);
struct ticker *ticker = (void *)atomic_exchange(¤t_thread->alarm_ticker, NULL);
if(ticker) {
if(ticker_delete(ticker, ¤t_thread->alarm_timeout) != -ENOENT)
tm_thread_put(current_thread);
}
linkedlist_remove(¤t_process->threadlist, ¤t_thread->pnode);
tm_thread_remove_kerfs_entries(current_thread);
atomic_fetch_sub_explicit(&running_threads, 1, memory_order_relaxed);
if(atomic_fetch_sub(¤t_process->thread_count, 1) == 1) {
atomic_fetch_sub_explicit(&running_processes, 1, memory_order_relaxed);
tm_process_remove_kerfs_entries(current_process);
tm_process_exit(current_thread->exit_code);
}
cpu_disable_preemption();
assert(!current_thread->blocklist);
tqueue_remove(current_thread->cpu->active_queue, ¤t_thread->activenode);
atomic_fetch_sub_explicit(¤t_thread->cpu->numtasks, 1, memory_order_relaxed);
tm_thread_raise_flag(current_thread, THREAD_SCHEDULE);
current_thread->state = THREADSTATE_DEAD;
workqueue_insert(&__current_cpu->work, thread_cleanup_call);
cpu_interrupt_set(0); /* don't schedule away until we get back
to the syscall handler! */
cpu_enable_preemption();
}
static int __pthread_rwlock_timedwrlock(pthread_rwlock_internal_t* rwlock,
const timespec* abs_timeout_or_null) {
if (__predict_false(__get_thread()->tid == atomic_load_explicit(&rwlock->writer_thread_id,
memory_order_relaxed))) {
return EDEADLK;
}
while (true) {
int old_state = atomic_load_explicit(&rwlock->state, memory_order_relaxed);
if (__predict_true(old_state == 0)) {
if (atomic_compare_exchange_weak_explicit(&rwlock->state, &old_state, -1,
memory_order_acquire, memory_order_relaxed)) {
// writer_thread_id is protected by rwlock and can only be modified in rwlock write
// owner thread. Other threads may read it for EDEADLK error checking, atomic operation
// is safe enough for it.
atomic_store_explicit(&rwlock->writer_thread_id, __get_thread()->tid, memory_order_relaxed);
return 0;
}
} else {
timespec ts;
timespec* rel_timeout = NULL;
if (abs_timeout_or_null != NULL) {
rel_timeout = &ts;
if (!timespec_from_absolute_timespec(*rel_timeout, *abs_timeout_or_null, CLOCK_REALTIME)) {
return ETIMEDOUT;
}
}
// To avoid losing wake ups, the pending_writers increment should be observed before
// futex_wait by all threads. A seq_cst fence instead of a seq_cst operation is used
// here. Because only a seq_cst fence can ensure sequential consistency for non-atomic
// operations in futex_wait.
atomic_fetch_add_explicit(&rwlock->pending_writers, 1, memory_order_relaxed);
atomic_thread_fence(memory_order_seq_cst);
int ret = __futex_wait_ex(&rwlock->state, rwlock->process_shared(), old_state,
rel_timeout);
atomic_fetch_sub_explicit(&rwlock->pending_writers, 1, memory_order_relaxed);
if (ret == -ETIMEDOUT) {
return ETIMEDOUT;
}
}
}
}
int pthread_rwlock_unlock(pthread_rwlock_t* rwlock_interface) {
pthread_rwlock_internal_t* rwlock = __get_internal_rwlock(rwlock_interface);
int old_state = atomic_load_explicit(&rwlock->state, memory_order_relaxed);
if (__state_owned_by_writer(old_state)) {
if (atomic_load_explicit(&rwlock->writer_tid, memory_order_relaxed) != __get_thread()->tid) {
return EPERM;
}
atomic_store_explicit(&rwlock->writer_tid, 0, memory_order_relaxed);
old_state = atomic_fetch_and_explicit(&rwlock->state, ~STATE_OWNED_BY_WRITER_FLAG,
memory_order_release);
if (!__state_have_pending_readers_or_writers(old_state)) {
return 0;
}
} else if (__state_owned_by_readers(old_state)) {
old_state = atomic_fetch_sub_explicit(&rwlock->state, STATE_READER_COUNT_CHANGE_STEP,
memory_order_release);
if (!__state_is_last_reader(old_state) || !__state_have_pending_readers_or_writers(old_state)) {
return 0;
}
} else {
return EPERM;
}
// Wake up pending readers or writers.
rwlock->pending_lock.lock();
if (rwlock->pending_writer_count != 0) {
rwlock->pending_writer_wakeup_serial++;
rwlock->pending_lock.unlock();
__futex_wake_ex(&rwlock->pending_writer_wakeup_serial, rwlock->pshared, 1);
} else if (rwlock->pending_reader_count != 0) {
rwlock->pending_reader_wakeup_serial++;
rwlock->pending_lock.unlock();
__futex_wake_ex(&rwlock->pending_reader_wakeup_serial, rwlock->pshared, INT_MAX);
} else {
// It happens when waiters are woken up by timeout.
rwlock->pending_lock.unlock();
}
return 0;
}
void mrqd_rlock(void * lock) {
MRQDLock *l = (MRQDLock*)lock;
bool bRaised = false;
int readPatience = 0;
start:
rgri_arrive(&l->readIndicator);
if(tatas_is_locked(&l->mutexLock)) {
rgri_depart(&l->readIndicator);
while(tatas_is_locked(&l->mutexLock)) {
thread_yield();
if((readPatience == MRQD_READ_PATIENCE_LIMIT) && !bRaised) {
atomic_fetch_add_explicit(&l->writeBarrier.value, 1, memory_order_seq_cst);
bRaised = true;
}
readPatience = readPatience + 1;
}
goto start;
}
if(bRaised) {
atomic_fetch_sub_explicit(&l->writeBarrier.value, 1, memory_order_seq_cst);
}
}
/**
* Update speed meter.
* @param[in] speed
* @param[in] count
*/
void spdm_update(struct speed_meter *speed, uint64_t count)
{
uint64_t curr_time = zclock(false);
uint64_t last_update = atomic_load_explicit(&speed->last_update, memory_order_acquire);
if (curr_time - last_update >= SEC2USEC(1)) {
if (atomic_compare_exchange_strong_explicit(&speed->last_update, &last_update, curr_time, memory_order_release,
memory_order_relaxed)) {
size_t i = atomic_load_explicit(&speed->i, memory_order_acquire);
uint64_t speed_aux = atomic_load_explicit(&speed->speed_aux, memory_order_acquire);
atomic_store_explicit(&speed->backlog[i].speed, speed_aux, memory_order_release);
atomic_fetch_sub_explicit(&speed->speed_aux, speed_aux, memory_order_release);
atomic_store_explicit(&speed->backlog[i].timestamp, last_update, memory_order_release);
i++;
if (SPEED_METER_BACKLOG == i) {
i = 0;
}
atomic_store_explicit(&speed->i, i, memory_order_release);
}
}
atomic_fetch_add_explicit(&speed->speed_aux, count, memory_order_release);
}
/** Finalize DALEC. Must be called before MPI is finalized. DALEC calls are
* not valid after finalization. Collective on world group.
*
* @return Zero on success
*/
int PDALEC_Finalize(void)
{
int dalec_alive = atomic_fetch_sub_explicit(&(DALECI_GLOBAL_STATE.alive),
1,memory_order_seq_cst);
if (dalec_alive == 1) {
/* Check for MPI initialization */
int mpi_is_init, mpi_is_fin;
MPI_Initialized(&mpi_is_init);
MPI_Finalized(&mpi_is_fin);
/* Free communicator if possible and return */
if (!mpi_is_init || mpi_is_fin) {
DALECI_Warning("MPI must be active when calling DALEC_Finalize");
return DALEC_ERROR_MPI_USAGE;
} else {
int rc = MPI_Comm_free(&DALECI_GLOBAL_STATE.mpi_comm);
return DALECI_Check_MPI("DALEC_Finalize", "MPI_Comm_free", rc);
}
} else {
/* Library is still active. */
return DALEC_SUCCESS;
}
}
/**
* Authenticate and set client info.
* @param[in] sess Client session.
* @return Zero on success (or one of *_RC).
*/
static int session_authenticate(struct zsession *sess)
{
int ret = OTHER_RC;
VALUE_PAIR *request_attrs = NULL, *response_attrs = NULL, *attrs = NULL;
char msg[8192]; // WARNING: libfreeradius-client has unsafe working with this buffer.
rc_handle *rh = zinst()->radh;
struct in_addr ip_addr;
char ip_str[INET_ADDRSTRLEN];
struct zcrules rules;
crules_init(&rules);
ip_addr.s_addr = htonl(sess->ip);
if (unlikely(NULL == inet_ntop(AF_INET, &ip_addr, ip_str, sizeof(ip_str)))) {
goto end;
}
if (unlikely(NULL == rc_avpair_add(rh, &request_attrs, PW_USER_NAME, ip_str, -1, 0))) {
goto end;
}
if (unlikely(NULL == rc_avpair_add(rh, &request_attrs, PW_USER_PASSWORD, "", -1, 0))) {
goto end;
}
if (unlikely(NULL == rc_avpair_add(rh, &request_attrs, PW_NAS_IDENTIFIER, zcfg()->radius_nas_identifier, -1, 0))) {
goto end;
}
if (unlikely(NULL == rc_avpair_add(rh, &request_attrs, PW_CALLING_STATION_ID, ip_str, -1, 0))) {
goto end;
}
ret = rc_auth(rh, 0, request_attrs, &response_attrs, msg);
if (OK_RC != ret) {
ZERO_LOG(LOG_ERR, "Session authentication failed for %s (code:%d)", ip_str, ret);
goto end;
}
attrs = response_attrs;
while (likely(NULL != attrs)) {
switch (attrs->attribute) {
case PW_FILTER_ID:
crules_parse(&rules, attrs->strvalue);
break;
case PW_SESSION_TIMEOUT:
atomic_store_explicit(&sess->max_duration, SEC2USEC(attrs->lvalue), memory_order_release);
break;
case PW_ACCT_INTERIM_INTERVAL:
atomic_store_explicit(&sess->acct_interval, SEC2USEC(attrs->lvalue), memory_order_release);
break;
}
attrs = attrs->next;
}
if (likely(rules.have.user_id && rules.have.login)) {
struct zclient *client = sess->client;
client_db_find_or_set_id(zinst()->client_db, rules.user_id, &client);
if (client != sess->client) {
// found
pthread_rwlock_wrlock(&sess->lock_client);
atomic_fetch_add_explicit(&client->refcnt, 1, memory_order_relaxed);
client_release(sess->client);
sess->client = client;
client_session_add(sess->client, sess);
pthread_rwlock_unlock(&sess->lock_client);
} else {
client_apply_rules(sess->client, &rules);
}
atomic_fetch_sub_explicit(&zinst()->unauth_sessions_cnt, 1, memory_order_release);
// log successful authentication
{
UT_string rules_str;
utstring_init(&rules_str);
utstring_reserve(&rules_str, 1024);
attrs = response_attrs;
while (likely(NULL != attrs)) {
switch (attrs->attribute) {
case PW_FILTER_ID:
utstring_printf(&rules_str, " %s", attrs->strvalue);
break;
default:
break;
}
attrs = attrs->next;
}
zero_syslog(LOG_INFO, "Authenticated session %s (rules:%s)", ip_str, utstring_body(&rules_str));
utstring_done(&rules_str);
}
} else {
ret = OTHER_RC;
ZERO_LOG(LOG_ERR, "Session authentication failed for %s (code:%d)", ip_str, ret);
}
end:
crules_free(&rules);
if (request_attrs) rc_avpair_free(request_attrs);
if (response_attrs) rc_avpair_free(response_attrs);
return ret;
}
/**
* Send radius accounting packet.
* @param[in] sess Session
* @param[in] status Accounting status (PW_STATUS_START, PW_STATUS_STOP, PW_STATUS_ALIVE)
* @param[in] cause Accounting termination cause (used only in case of PW_STATUS_STOP)
* @return Zero on success (one of *_RC codes).
*/
static int session_accounting(struct zsession *sess, uint32_t status, uint32_t term_cause)
{
int ret = OTHER_RC;
VALUE_PAIR *request_attrs = NULL;
rc_handle *rh = zinst()->radh;
struct in_addr ip_addr;
char ip_str[INET_ADDRSTRLEN];
uint64_t traff_down = atomic_load_explicit(&sess->traff_down, memory_order_acquire);
uint64_t traff_up = atomic_load_explicit(&sess->traff_up, memory_order_acquire);
uint32_t octets_down = (uint32_t) (traff_down % UINT32_MAX);
uint32_t octets_up = (uint32_t) (traff_up % UINT32_MAX);
uint32_t packets_down = atomic_load_explicit(&sess->packets_down, memory_order_acquire) % UINT32_MAX;
uint32_t packets_up = atomic_load_explicit(&sess->packets_up, memory_order_acquire) % UINT32_MAX;
uint32_t gigawords_down = 0;
uint32_t gigawords_up = 0;
char session_id[255];
snprintf(session_id, sizeof(session_id), "%s-%" PRIu32, sess->client->login, sess->ip);
ip_addr.s_addr = htonl(sess->ip);
if (unlikely(NULL == inet_ntop(AF_INET, &ip_addr, ip_str, sizeof(ip_str)))) {
goto end;
}
if (unlikely(NULL == rc_avpair_add(rh, &request_attrs, PW_CALLING_STATION_ID, ip_str, -1, 0))) {
goto end;
}
if (unlikely(NULL == rc_avpair_add(rh, &request_attrs, PW_FRAMED_IP_ADDRESS, &sess->ip, -1, 0))) {
goto end;
}
if (unlikely(NULL == rc_avpair_add(rh, &request_attrs, PW_USER_NAME, sess->client->login, -1, 0))) {
goto end;
}
if (unlikely(NULL == rc_avpair_add(rh, &request_attrs, PW_ACCT_SESSION_ID, session_id, -1, 0))) {
goto end;
}
if (unlikely(NULL == rc_avpair_add(rh, &request_attrs, PW_NAS_IDENTIFIER, zcfg()->radius_nas_identifier, -1, 0))) {
goto end;
}
if (PW_STATUS_STOP == status) {
if (unlikely(NULL == rc_avpair_add(rh, &request_attrs, PW_ACCT_TERMINATE_CAUSE, &term_cause, -1, 0))) {
goto end;
}
}
if (unlikely(NULL == rc_avpair_add(rh, &request_attrs, PW_ACCT_STATUS_TYPE, &status, -1, 0))) {
goto end;
}
if (unlikely(NULL == rc_avpair_add(rh, &request_attrs, PW_ACCT_INPUT_OCTETS, &octets_down, -1, 0))) {
goto end;
}
if (unlikely(NULL == rc_avpair_add(rh, &request_attrs, PW_ACCT_INPUT_PACKETS, &packets_down, -1, 0))) {
goto end;
}
if (unlikely(NULL == rc_avpair_add(rh, &request_attrs, PW_ACCT_OUTPUT_OCTETS, &octets_up, -1, 0))) {
goto end;
}
if (unlikely(NULL == rc_avpair_add(rh, &request_attrs, PW_ACCT_OUTPUT_PACKETS, &packets_down, -1, 0))) {
goto end;
}
if (unlikely(UINT32_MAX < traff_down)) {
gigawords_down = (uint32_t) (traff_down / UINT32_MAX);
if (unlikely(NULL == rc_avpair_add(rh, &request_attrs, PW_ACCT_INPUT_GIGAWORDS, &gigawords_down, -1, 0))) {
goto end;
}
}
if (unlikely(UINT32_MAX < traff_up)) {
gigawords_up = (uint32_t) (traff_up / UINT32_MAX);
if (unlikely(NULL == rc_avpair_add(rh, &request_attrs, PW_ACCT_OUTPUT_GIGAWORDS, &gigawords_up, -1, 0))) {
goto end;
}
}
ret = rc_acct(rh, 0, request_attrs);
if (unlikely(OK_RC != ret)) {
ZERO_LOG(LOG_ERR, "radius accounting failed %s (code:%d)", ip_str, ret);
goto end;
}
atomic_fetch_sub_explicit(&sess->traff_down, traff_down, memory_order_release);
atomic_fetch_sub_explicit(&sess->traff_up, traff_up, memory_order_release);
atomic_fetch_sub_explicit(&sess->packets_down, packets_down, memory_order_release);
atomic_fetch_sub_explicit(&sess->packets_up, packets_up, memory_order_release);
end:
if (request_attrs) {
rc_avpair_free(request_attrs);
}
return ret;
}
void ponyint_asio_noisy_remove()
{
atomic_fetch_sub_explicit(&running_base.noisy_count, 1, memory_order_relaxed);
}
TEST(stdatomic, atomic_fetch_sub) {
atomic_int i = ATOMIC_VAR_INIT(123);
ASSERT_EQ(123, atomic_fetch_sub(&i, 1));
ASSERT_EQ(122, atomic_fetch_sub_explicit(&i, 1, memory_order_relaxed));
ASSERT_EQ(121, atomic_load(&i));
}