runtime: fix handling of network deadlines

Ensure that deadlines affect already issued IO.

R=golang-dev, mikioh.mikioh, bradfitz
CC=golang-dev
https://golang.org/cl/12847043

src/pkg/net/fd_poll_unix.go

@@ -351,20 +351,29 @@ func (pd *pollDesc) Init(fd *netFD) error {
 	return nil
 }
 
-// TODO(dfc) these unused error returns could be removed
-
 func (fd *netFD) setDeadline(t time.Time) error {
-	fd.setReadDeadline(t)
-	fd.setWriteDeadline(t)
-	return nil
+	return setDeadlineImpl(fd, t, true, true)
 }
 
 func (fd *netFD) setReadDeadline(t time.Time) error {
-	fd.pd.rdeadline.setTime(t)
-	return nil
+	return setDeadlineImpl(fd, t, true, false)
 }
 
 func (fd *netFD) setWriteDeadline(t time.Time) error {
-	fd.pd.wdeadline.setTime(t)
+	return setDeadlineImpl(fd, t, false, true)
+}
+
+func setDeadlineImpl(fd *netFD, t time.Time, read, write bool) error {
+	if err := fd.incref(); err != nil {
+		return err
+	}
+	defer fd.decref()
+	if read {
+		fd.pd.rdeadline.setTime(t)
+	}
+	if write {
+		fd.pd.wdeadline.setTime(t)
+	}
+	fd.pd.Wakeup()
 	return nil
 }

src/pkg/runtime/netpoll.goc

@@ -134,9 +134,13 @@ func runtime_pollWaitCanceled(pd *PollDesc, mode int) {
 }
 
 func runtime_pollSetDeadline(pd *PollDesc, d int64, mode int) {
+	G *rg, *wg;
+
 	runtime·lock(pd);
-	if(pd->closing)
-		goto ret;
+	if(pd->closing) {
+		runtime·unlock(pd);
+		return;
+	}
 	pd->seq++;  // invalidate current timers
 	// Reset current timers.
 	if(pd->rt.fv) {
@@ -148,9 +152,8 @@ func runtime_pollSetDeadline(pd *PollDesc, d int64, mode int) {
 		pd->wt.fv = nil;
 	}
 	// Setup new timers.
-	if(d != 0 && d <= runtime·nanotime()) {
+	if(d != 0 && d <= runtime·nanotime())
 		d = -1;
-	}
 	if(mode == 'r' || mode == 'r'+'w')
 		pd->rd = d;
 	if(mode == 'w' || mode == 'r'+'w')
@@ -180,8 +183,18 @@ func runtime_pollSetDeadline(pd *PollDesc, d int64, mode int) {
 			runtime·addtimer(&pd->wt);
 		}
 	}
-ret:
+	// If we set the new deadline in the past, unblock currently pending IO if any.
+	rg = nil;
+	wg = nil;
+	if(pd->rd < 0)
+		rg = netpollunblock(pd, 'r', false);
+	if(pd->wd < 0)
+		wg = netpollunblock(pd, 'w', false);
 	runtime·unlock(pd);
+	if(rg)
+		runtime·ready(rg);
+	if(wg)
+		runtime·ready(wg);
 }
 
 func runtime_pollUnblock(pd *PollDesc) {