Function wait_pthread

src/bthread/butex.cpp:148–189

bool erase_from_butex(ButexWaiter*, bool, WaiterState);

int wait_pthread(ButexPthreadWaiter& pw, const timespec* abstime) {
    timespec* ptimeout = NULL;
    timespec timeout;
    int64_t timeout_us = 0;
    int rc;

    while (true) {
        if (abstime != NULL) {
            timeout_us = butil::timespec_to_microseconds(*abstime) - butil::gettimeofday_us();
            timeout = butil::microseconds_to_timespec(timeout_us);
            ptimeout = &timeout;
        }
        if (timeout_us > MIN_SLEEP_US || abstime == NULL) {
            rc = futex_wait_private(&pw.sig, PTHREAD_NOT_SIGNALLED, ptimeout);
            if (PTHREAD_NOT_SIGNALLED != pw.sig.load(butil::memory_order_acquire)) {
                // If `sig' is changed, wakeup_pthread() must be called and `pw'
                // is already removed from the butex.
                // Acquire fence makes this thread sees changes before wakeup.
                return rc;
            }
        } else {
            errno = ETIMEDOUT;
            rc = -1;
        }
        // Handle ETIMEDOUT when abstime is valid.
        // If futex_wait_private return EINTR, just continue the loop.
        if (rc != 0 && errno == ETIMEDOUT) {
            // wait futex timeout, `pw' is still in the queue, remove it.
            if (!erase_from_butex(&pw, false, WAITER_STATE_TIMEDOUT)) {
                // Another thread is erasing `pw' as well, wait for the signal.
                // Acquire fence makes this thread sees changes before wakeup.
                if (pw.sig.load(butil::memory_order_acquire) == PTHREAD_NOT_SIGNALLED) {
                    // already timedout, abstime and ptimeout are expired.
                    abstime = NULL;
                    ptimeout = NULL;
                    continue;
                }
            }
            return rc;
        }
    }
}

extern BAIDU_THREAD_LOCAL TaskGroup* tls_task_group;