You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: timestamp_barrier.go
    path of file: ./repos/cockroach/pkg/ccl/changefeedccl/schemafeed
    
    the code of the file until where you have to start completion: // Copyright 2024 The Cockroach Authors.
//
// Licensed as a CockroachDB Enterprise file under the Cockroach Community
// License (the "License"); you may not use this file except in compliance with
// the License. You may obtain a copy of the License at
//
//     https://github.com/cockroachdb/cockroach/blob/master/licenses/CCL.txt

package schemafeed

import (
	"github.com/cockroachdb/cockroach/pkg/util/hlc"
	"github.com/cockroachdb/errors"
)

// A timestampBarrier is used to synchronize goroutines that advance a monotonically
// increasing frontier timestamp and goroutines that need to wait for the
// frontier to advance past a specific timestamp.
//
// A monotonically decreasing error timestamp can also 
    
func (m *timestampBarrier) setError(ts hlc.Timestamp, err error) error {
	if ts.LessEq(m.frontier) {
		return errors.AssertionFailedf(
			"cannot set error timestamp to %s, which is earlier or equal to the current frontier %s", ts, m.frontier)
	}
	if err == nil {
		return errors.AssertionFailedf("cannot set nil error for timestamp %s", ts)
	}
	if m.errTS.IsSet() && m.errTS.LessEq(ts) {
		return nil
	}
	m.errTS = ts
	m.err = err

	// Signal all waiters that are waiting at or after the new error timestamp.
	newWaiters := make([]timestampWaiter, 0, len(m.waiters))
	for _, w := range m.waiters {
		if !w.ts.Less(m.errTS) {
			w.errCh <- m.err
			close(w.errCh)
			continue
		}
		newWaiters = append(newWaiters, w)
	}
	m.waiters = newWaiters

	return nil
}