+/**
+ * Releases the block on a thread created by _Jv_ThreadPark(). This
+ * method can also be used to terminate a blockage caused by a prior
+ * call to park. This operation is unsafe, as the thread must be
+ * guaranteed to be live.
+ *
+ * @param thread the thread to unblock.
+ */
+void
+ParkHelper::unpark ()
+{
+ using namespace ::java::lang;
+ volatile obj_addr_t *ptr = &permit;
+
+ /* If this thread is in state RUNNING, give it a permit and return
+ immediately. */
+ if (compare_and_swap
+ (ptr, Thread::THREAD_PARK_RUNNING, Thread::THREAD_PARK_PERMIT))
+ return;
+
+ /* If this thread is parked, put it into state RUNNING and send it a
+ signal. */
+ if (compare_and_swap
+ (ptr, Thread::THREAD_PARK_PARKED, Thread::THREAD_PARK_RUNNING))
+ {
+ int result;
+ pthread_mutex_lock (&mutex);
+ result = pthread_cond_signal (&cond);
+ pthread_mutex_unlock (&mutex);
+ JvAssert (result == 0);
+ }
+}
+
+/**
+ * Sets our state to dead.
+ */
+void
+ParkHelper::deactivate ()
+{
+ permit = ::java::lang::Thread::THREAD_PARK_DEAD;
+}
+
+void
+ParkHelper::init ()
+{
+ pthread_mutex_init (&mutex, NULL);
+ pthread_cond_init (&cond, NULL);
+ permit = ::java::lang::Thread::THREAD_PARK_RUNNING;
+}
+
+/**
+ * Blocks the thread until a matching _Jv_ThreadUnpark() occurs, the
+ * thread is interrupted or the optional timeout expires. If an
+ * unpark call has already occurred, this also counts. A timeout
+ * value of zero is defined as no timeout. When isAbsolute is true,
+ * the timeout is in milliseconds relative to the epoch. Otherwise,
+ * the value is the number of nanoseconds which must occur before
+ * timeout. This call may also return spuriously (i.e. for no
+ * apparent reason).
+ *
+ * @param isAbsolute true if the timeout is specified in milliseconds from
+ * the epoch.
+ * @param time either the number of nanoseconds to wait, or a time in
+ * milliseconds from the epoch to wait for.
+ */
+void
+ParkHelper::park (jboolean isAbsolute, jlong time)
+{
+ using namespace ::java::lang;
+ volatile obj_addr_t *ptr = &permit;
+
+ /* If we have a permit, return immediately. */
+ if (compare_and_swap
+ (ptr, Thread::THREAD_PARK_PERMIT, Thread::THREAD_PARK_RUNNING))
+ return;
+
+ struct timespec ts;
+
+ if (time)
+ {
+ unsigned long long seconds;
+ unsigned long usec;
+
+ if (isAbsolute)
+ {
+ ts.tv_sec = time / 1000;
+ ts.tv_nsec = (time % 1000) * 1000 * 1000;
+ }
+ else
+ {
+ // Calculate the abstime corresponding to the timeout.
+ jlong nanos = time;
+ jlong millis = 0;
+
+ // For better accuracy, should use pthread_condattr_setclock
+ // and clock_gettime.
+#ifdef HAVE_GETTIMEOFDAY
+ timeval tv;
+ gettimeofday (&tv, NULL);
+ usec = tv.tv_usec;
+ seconds = tv.tv_sec;
+#else
+ unsigned long long startTime
+ = java::lang::System::currentTimeMillis();
+ seconds = startTime / 1000;
+ /* Assume we're about half-way through this millisecond. */
+ usec = (startTime % 1000) * 1000 + 500;
+#endif
+ /* These next two statements cannot overflow. */
+ usec += nanos / 1000;
+ usec += (millis % 1000) * 1000;
+ /* These two statements could overflow only if tv.tv_sec was
+ insanely large. */
+ seconds += millis / 1000;
+ seconds += usec / 1000000;
+
+ ts.tv_sec = seconds;
+ if (ts.tv_sec < 0 || (unsigned long long)ts.tv_sec != seconds)
+ {
+ // We treat a timeout that won't fit into a struct timespec
+ // as a wait forever.
+ millis = nanos = 0;
+ }
+ else
+ /* This next statement also cannot overflow. */
+ ts.tv_nsec = (usec % 1000000) * 1000 + (nanos % 1000);
+ }
+ }
+
+ pthread_mutex_lock (&mutex);
+ if (compare_and_swap
+ (ptr, Thread::THREAD_PARK_RUNNING, Thread::THREAD_PARK_PARKED))
+ {
+ int result = 0;
+
+ if (! time)
+ result = pthread_cond_wait (&cond, &mutex);
+ else
+ result = pthread_cond_timedwait (&cond, &mutex, &ts);
+
+ JvAssert (result == 0 || result == ETIMEDOUT);
+
+ /* If we were unparked by some other thread, this will already
+ be in state THREAD_PARK_RUNNING. If we timed out or were
+ interrupted, we have to do it ourself. */
+ permit = Thread::THREAD_PARK_RUNNING;
+ }
+ pthread_mutex_unlock (&mutex);
+}
+