syscall: don't cache environment variables on Plan 9

Fixes #8849.

LGTM=bradfitz, aram
R=bradfitz, rsc, aram
CC=golang-codereviews
https://golang.org/cl/158970045

diff --git a/src/syscall/env_plan9.go b/src/syscall/env_plan9.go
index 934507905297445a039df14fb99b299d2be85e6d..9ea36c886abd1e6b80590081e3f7ed184c8745f1 100644 (file)
--- a/src/syscall/env_plan9.go
+++ b/src/syscall/env_plan9.go
@@ -8,28 +8,9 @@ package syscall
 
 import (
        "errors"
-       "sync"
 )
 
 var (
-       // envOnce guards copyenv, which populates env, envi and envs.
-       envOnce sync.Once
-
-       // envLock guards env, envi and envs.
-       envLock sync.RWMutex
-
-       // env maps from an environment variable to its value.
-       // TODO: remove this? golang.org/issue/8849
-       env = make(map[string]string)
-
-       // envi maps from an environment variable to its index in envs.
-       // TODO: remove this? golang.org/issue/8849
-       envi = make(map[string]int)
-
-       // envs contains elements of env in the form "key=value".
-       // empty strings mean deleted.
-       envs []string
-
        errZeroLengthKey = errors.New("zero length key")
        errShortWrite    = errors.New("i/o count too small")
 )
@@ -70,47 +51,14 @@ func writeenv(key, value string) error {
        return nil
 }
 
-func copyenv() {
-       fd, err := Open("/env", O_RDONLY)
-       if err != nil {
-               return
-       }
-       defer Close(fd)
-       files, err := readdirnames(fd)
-       if err != nil {
-               return
-       }
-       envs = make([]string, len(files))
-       i := 0
-       for _, key := range files {
-               v, err := readenv(key)
-               if err != nil {
-                       continue
-               }
-               env[key] = v
-               envs[i] = key + "=" + v
-               envi[key] = i
-               i++
-       }
-}
-
 func Getenv(key string) (value string, found bool) {
        if len(key) == 0 {
                return "", false
        }
-
-       envLock.RLock()
-       defer envLock.RUnlock()
-
-       if v, ok := env[key]; ok {
-               return v, true
-       }
        v, err := readenv(key)
        if err != nil {
                return "", false
        }
-       env[key] = v
-       envs = append(envs, key+"="+v)
        return v, true
 }
 
@@ -118,27 +66,14 @@ func Setenv(key, value string) error {
        if len(key) == 0 {
                return errZeroLengthKey
        }
-
-       envLock.Lock()
-       defer envLock.Unlock()
-
        err := writeenv(key, value)
        if err != nil {
                return err
        }
-       env[key] = value
-       envs = append(envs, key+"="+value)
-       envi[key] = len(envs) - 1
        return nil
 }
 
 func Clearenv() {
-       envLock.Lock()
-       defer envLock.Unlock()
-
-       env = make(map[string]string)
-       envi = make(map[string]int)
-       envs = []string{}
        RawSyscall(SYS_RFORK, RFCENVG, 0, 0)
 }
 
@@ -146,30 +81,28 @@ func Unsetenv(key string) error {
        if len(key) == 0 {
                return errZeroLengthKey
        }
-
-       envLock.Lock()
-       defer envLock.Unlock()
-
        Remove("/env/" + key)
-
-       if i, ok := envi[key]; ok {
-               delete(env, key)
-               delete(envi, key)
-               envs[i] = ""
-       }
        return nil
 }
 
 func Environ() []string {
-       envLock.RLock()
-       defer envLock.RUnlock()
+       fd, err := Open("/env", O_RDONLY)
+       if err != nil {
+               return nil
+       }
+       defer Close(fd)
+       files, err := readdirnames(fd)
+       if err != nil {
+               return nil
+       }
+       ret := make([]string, 0, len(files))
 
-       envOnce.Do(copyenv)
-       ret := make([]string, 0, len(envs))
-       for _, pair := range envs {
-               if pair != "" {
-                       ret = append(ret, pair)
+       for _, key := range files {
+               v, err := readenv(key)
+               if err != nil {
+                       continue
                }
+               ret = append(ret, key+"="+v)
        }
        return ret
 }