libgo/go/syscall/pwd_plan9.go

   1 // Copyright 2015 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 // The working directory in Plan 9 is effectively per P, so different
   6 // goroutines and even the same goroutine as it's rescheduled on
   7 // different Ps can see different working directories.
   8 //
   9 // Instead, track a Go process-wide intent of the current working directory,
  10 // and switch to it at important points.
  11
  12 package syscall
  13
  14 import "sync"
  15
  16 var (
  17         wdmu  sync.Mutex // guards following
  18         wdSet bool
  19         wdStr string
  20 )
  21
  22 func Fixwd() {
  23         wdmu.Lock()
  24         defer wdmu.Unlock()
  25         fixwdLocked()
  26 }
  27
  28 func fixwdLocked() {
  29         if !wdSet {
  30                 return
  31         }
  32         // always call chdir when getwd returns an error
  33         wd, _ := getwd()
  34         if wd == wdStr {
  35                 return
  36         }
  37         if err := chdir(wdStr); err != nil {
  38                 return
  39         }
  40 }
  41
  42 // goroutine-specific getwd
  43 func getwd() (wd string, err error) {
  44         fd, err := open(".", O_RDONLY)
  45         if err != nil {
  46                 return "", err
  47         }
  48         defer Close(fd)
  49         return Fd2path(fd)
  50 }
  51
  52 func Getwd() (wd string, err error) {
  53         wdmu.Lock()
  54         defer wdmu.Unlock()
  55
  56         if wdSet {
  57                 return wdStr, nil
  58         }
  59         wd, err = getwd()
  60         if err != nil {
  61                 return
  62         }
  63         wdSet = true
  64         wdStr = wd
  65         return wd, nil
  66 }
  67
  68 func Chdir(path string) error {
  69         wdmu.Lock()
  70         defer wdmu.Unlock()
  71
  72         if err := chdir(path); err != nil {
  73                 return err
  74         }
  75
  76         wd, err := getwd()
  77         if err != nil {
  78                 return err
  79         }
  80         wdSet = true
  81         wdStr = wd
  82         return nil
  83 }