net: let OS-specific AddFD routine wake up polling thread.

With gccgo some operating systems require using select rather
than epoll or kevent.  Using select means that we have to wake
up the polling thread each time we add a new file descriptor.
This implements that in the generic code rather than adding
another wakeup channel, even though nothing in the current net
package uses the capability.

R=rsc, iant2
CC=golang-dev
https://golang.org/cl/4284069

src/pkg/net/fd.go

@@ -122,9 +122,13 @@ func (s *pollServer) AddFD(fd *netFD, mode int) {
 		doWakeup = true
 	}
 
-	if err := s.poll.AddFD(intfd, mode, false); err != nil {
+	wake, err := s.poll.AddFD(intfd, mode, false)
+	if err != nil {
 		panic("pollServer AddFD " + err.String())
 	}
+	if wake {
+		doWakeup = true
+	}
 
 	s.Unlock()
 

src/pkg/net/fd_darwin.go

@@ -31,7 +31,7 @@ func newpollster() (p *pollster, err os.Error) {
 	return p, nil
 }
 
-func (p *pollster) AddFD(fd int, mode int, repeat bool) os.Error {
+func (p *pollster) AddFD(fd int, mode int, repeat bool) (bool, os.Error) {
 	// pollServer is locked.
 
 	var kmode int
@@ -53,15 +53,15 @@ func (p *pollster) AddFD(fd int, mode int, repeat bool) os.Error {
 
 	n, e := syscall.Kevent(p.kq, p.kbuf[0:], p.kbuf[0:], nil)
 	if e != 0 {
-		return os.NewSyscallError("kevent", e)
+		return false, os.NewSyscallError("kevent", e)
 	}
 	if n != 1 || (ev.Flags&syscall.EV_ERROR) == 0 || int(ev.Ident) != fd || int(ev.Filter) != kmode {
-		return os.ErrorString("kqueue phase error")
+		return false, os.ErrorString("kqueue phase error")
 	}
 	if ev.Data != 0 {
-		return os.Errno(int(ev.Data))
+		return false, os.Errno(int(ev.Data))
 	}
-	return nil
+	return false, nil
 }
 
 func (p *pollster) DelFD(fd int, mode int) {

src/pkg/net/fd_freebsd.go

@@ -31,7 +31,7 @@ func newpollster() (p *pollster, err os.Error) {
 	return p, nil
 }
 
-func (p *pollster) AddFD(fd int, mode int, repeat bool) os.Error {
+func (p *pollster) AddFD(fd int, mode int, repeat bool) (bool, os.Error) {
 	// pollServer is locked.
 
 	var kmode int
@@ -51,15 +51,15 @@ func (p *pollster) AddFD(fd int, mode int, repeat bool) os.Error {
 
 	n, e := syscall.Kevent(p.kq, p.kbuf[:], nil, nil)
 	if e != 0 {
-		return os.NewSyscallError("kevent", e)
+		return false, os.NewSyscallError("kevent", e)
 	}
 	if n != 1 || (ev.Flags&syscall.EV_ERROR) == 0 || int(ev.Ident) != fd || int(ev.Filter) != kmode {
-		return os.NewSyscallError("kqueue phase error", e)
+		return false, os.NewSyscallError("kqueue phase error", e)
 	}
 	if ev.Data != 0 {
-		return os.Errno(int(ev.Data))
+		return false, os.Errno(int(ev.Data))
 	}
-	return nil
+	return false, nil
 }
 
 func (p *pollster) DelFD(fd int, mode int) {

src/pkg/net/fd_linux.go

@@ -47,7 +47,7 @@ func newpollster() (p *pollster, err os.Error) {
 	return p, nil
 }
 
-func (p *pollster) AddFD(fd int, mode int, repeat bool) os.Error {
+func (p *pollster) AddFD(fd int, mode int, repeat bool) (bool, os.Error) {
 	// pollServer is locked.
 
 	var already bool
@@ -69,10 +69,10 @@ func (p *pollster) AddFD(fd int, mode int, repeat bool) os.Error {
 		op = syscall.EPOLL_CTL_ADD
 	}
 	if e := syscall.EpollCtl(p.epfd, op, fd, &p.ctlEvent); e != 0 {
-		return os.NewSyscallError("epoll_ctl", e)
+		return false, os.NewSyscallError("epoll_ctl", e)
 	}
 	p.events[fd] = p.ctlEvent.Events
-	return nil
+	return false, nil
 }
 
 func (p *pollster) StopWaiting(fd int, bits uint) {

src/pkg/net/newpollserver.go

@@ -31,7 +31,7 @@ func newPollServer() (s *pollServer, err os.Error) {
 	if s.poll, err = newpollster(); err != nil {
 		goto Error
 	}
-	if err = s.poll.AddFD(s.pr.Fd(), 'r', true); err != nil {
+	if _, err = s.poll.AddFD(s.pr.Fd(), 'r', true); err != nil {
 		s.poll.Close()
 		goto Error
 	}