code review 12418043: net: add special netFD mutex

src/pkg/net/fd_poll_runtime.go

 // 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 linux windows
 
 package net
 
 import (
         "sync"
@@ skipping 20 matching lines @@
         serverInit.Do(runtime_pollServerInit)
         ctx, errno := runtime_pollOpen(uintptr(fd.sysfd))
         if errno != 0 {
                 return syscall.Errno(errno)
         }
         pd.runtimeCtx = ctx
         return nil
 }
 
 func (pd *pollDesc) Close() {
+        if pd.runtimeCtx == 0 {
+                return
+        }
         runtime_pollClose(pd.runtimeCtx)
+        pd.runtimeCtx = 0
 }
 
 func (pd *pollDesc) Lock() {
 }
 
 func (pd *pollDesc) Unlock() {
 }
 
 func (pd *pollDesc) Wakeup() {
 }
 
 // Evict evicts fd from the pending list, unblocking any I/O running on fd.
 // Return value is whether the pollServer should be woken up.
 func (pd *pollDesc) Evict() bool {
+        if pd.runtimeCtx == 0 {
+                return false
+        }
         runtime_pollUnblock(pd.runtimeCtx)
         return false
 }
 
 func (pd *pollDesc) Prepare(mode int) error {
         res := runtime_pollReset(pd.runtimeCtx, mode)
         return convertErr(res)
 }
 
 func (pd *pollDesc) PrepareRead() error {
@@ skipping 52 matching lines @@
 
 func setDeadline(fd *netFD, t time.Time) error {
         return setDeadlineImpl(fd, t, 'r'+'w')
 }
 
 func setDeadlineImpl(fd *netFD, t time.Time, mode int) error {
         d := t.UnixNano()
         if t.IsZero() {
                 d = 0
         }
-        if err := fd.lock(false); err != nil {
+        if err := fd.incref(); err != nil {
                 return err
         }
         runtime_pollSetDeadline(fd.pd.runtimeCtx, d, mode)
-        fd.unlock()
+        fd.decref()
         return nil
 }