Fail loudly on a touch read, stop the workers before their sockets close, and file down the small edges

probe.go

@@ -170,10 +170,13 @@ func (p *probeSender) awaitTx(scratch, oob []byte) (int64, bool) {
 	fds := []unix.PollFd{{Fd: int32(p.fd), Events: unix.POLLERR}}
 	deadline := time.Now().Add(probeTimeout)
 	for {
-		ms := int(time.Until(deadline).Milliseconds())
-		if ms <= 0 {
+		left := time.Until(deadline)
+		if left <= 0 {
 			return 0, false
 		}
+		// Rounded up, since truncating would give up with time still on the
+		// clock and shave the last fraction of a millisecond off every wait.
+		ms := int((left + time.Millisecond - 1) / time.Millisecond)
 		n, err := unix.Poll(fds, ms)
 		if err == unix.EINTR {
 			continue