code review 12418043: net: add special netFD mutex

src/pkg/runtime/netpoll.goc

 // Copyright 2013 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
 // +build darwin freebsd,amd64 freebsd,386 linux openbsd windows
 
 package net
 
 #include "runtime.h"
 #include "defs_GOOS_GOARCH.h"
@@ skipping 196 matching lines @@
 }
 
 func runtime_Semacquire(addr *uint32) {
         runtime·semacquire(addr, true);
 }
 
 func runtime_Semrelease(addr *uint32) {
         runtime·semrelease(addr);
 }
 
+uintptr
+runtime·netpollfd(PollDesc *pd)
+{
+        return pd->fd;
+}
+
 // make pd ready, newly runnable goroutines (if any) are enqueued info gpp list
 void
 runtime·netpollready(G **gpp, PollDesc *pd, int32 mode)
 {
         G *rg, *wg;
 
         rg = wg = nil;
         runtime·lock(pd);
         if(mode == 'r' || mode == 'r'+'w')
                 rg = netpollunblock(pd, 'r', true);
@@ skipping 142 matching lines @@
                 for(i = 0; i < n; i++) {
                         pd[i].link = pollcache.first;
                         pollcache.first = &pd[i];
                 }
         }
         pd = pollcache.first;
         pollcache.first = pd->link;
         runtime·unlock(&pollcache);
         return pd;
 }