regions inside ParallelExecute op is blocked until all inputs to all regions
    are materialized and ops following ParallelExecute op are blocked until all
    regions are executed.
  }];

  let results = (outs
    Variadic<AnyType>:$execute_outputs
  );

  let regions = (region VariadicRegion<SizedRegion<1>>:$regions);

  let extraClassDeclaration = [{
    Block& GetRegionBlockWithIndex(unsigned index);

	state atomic.Uint64 // high 32 bits are counter, low 32 bits are waiter count.
	sema  uint32
}

// Add adds delta, which may be negative, to the [WaitGroup] counter.
// If the counter becomes zero, all goroutines blocked on [WaitGroup.Wait] are released.
// If the counter goes negative, Add panics.
//
// Note that calls with a positive delta that occur when the counter is zero

                            + "in this parallel build, those kind of mojos require exclusive access to "
                            + "reactor to prevent race conditions. This mojo execution will be blocked "
                            + "until the aggregator mojo is done.";
                    warn(msg);
                    acquiredAggregatorLock.lock();
                }

	preemptoff    string // if != "", keep curg running on this m
	locks         int32
	dying         int32
	profilehz     int32
	spinning      bool // m is out of work and is actively looking for work
	blocked       bool // m is blocked on a note
	newSigstack   bool // minit on C thread called sigaltstack
	printlock     int8
	incgo         bool          // m is executing a cgo call
	isextra       bool          // m is an extra m

	}
}

// blockableSig reports whether sig may be blocked by the signal mask.
// We never want to block the signals marked _SigUnblock;
// these are the synchronous signals that turn into a Go panic.
// We never want to block the preemption signal if it is being used.
// In a Go program--not a c-archive/c-shared--we never want to block
// the signals marked _SigKill or _SigThrow, as otherwise it's possible

func (rw *rwmutex) unlock() {
	// Announce to readers that there is no active writer.
	r := rw.readerCount.Add(rwmutexMaxReaders)
	if r >= rwmutexMaxReaders {
		throw("unlock of unlocked rwmutex")
	}
	// Unblock blocked readers.
	lock(&rw.rLock)
	for rw.readers.ptr() != nil {
		reader := rw.readers.ptr()
		rw.readers = reader.schedlink
		reader.schedlink.set(nil)
		notewakeup(&reader.park)
		r -= 1

	EvGoBlock             // goroutine blocks [timestamp, reason, stack ID]
	EvGoUnblock           // goroutine is unblocked [timestamp, goroutine ID, goroutine seq, stack ID]
	EvGoSyscallBegin      // syscall enter [timestamp, P seq, stack ID]
	EvGoSyscallEnd        // syscall exit [timestamp]
	EvGoSyscallEndBlocked // syscall exit and it blocked at some point [timestamp]

	})

	// Wait until process Q has either failed or locked file B.
	// Otherwise, P.2 might not block on file B as intended.
locked:
	for {
		if _, err := os.Stat(filepath.Join(dir, "locked")); !os.IsNotExist(err) {
			break locked
		}
		timer := time.NewTimer(1 * time.Millisecond)
		select {
		case <-qDone:
			timer.Stop()
			break locked
		case <-timer.C:
		}
	}

     * allows tasks in other projects to access the state of this project without deadlocks in cases where there are dependency cycles between projects. It also allows other non-taask work
     * to run while the task is blocked.
     *
     * <p>When parallel execution is not enabled, the lock is shared between projects within a build, and each build in the build tree has its own shared lock.
     */
    ResourceLock getTaskExecutionLock();

// from a placeholder node "arg_tensor_enqueue_<tensor_id>".
//
// `tensor` is still owned by the caller. This call will be blocked if the queue
// has reached its capacity, and will be unblocked when the queued tensors again
// drop below the capacity due to dequeuing.
//
// Tensors are dequeued via the corresponding TF dequeue op.
// TODO(hongm): Add support for `timeout_ms`.