diff --git a/src/os/dir_darwin.go b/src/os/dir_darwin.go
index e6d5bda24bdd490c2744c5cf5e4782fd72f1a709..91b67d8d61d1fc0f23a4cf0fce2db8364401efa8 100644
--- a/src/os/dir_darwin.go
+++ b/src/os/dir_darwin.go
@@ -25,16 +25,24 @@ func (d *dirInfo) close() {
}
func (f *File) readdir(n int, mode readdirMode) (names []string, dirents []DirEntry, infos []FileInfo, err error) {
- if f.dirinfo == nil {
+ // If this file has no dirinfo, create one.
+ var d *dirInfo
+ for {
+ d = f.dirinfo.Load()
+ if d != nil {
+ break
+ }
dir, call, errno := f.pfd.OpenDir()
if errno != nil {
return nil, nil, nil, &PathError{Op: call, Path: f.name, Err: errno}
}
- f.dirinfo = &dirInfo{
- dir: dir,
+ d = &dirInfo{dir: dir}
+ if f.dirinfo.CompareAndSwap(nil, d) {
+ break
}
+ // We lost the race: try again.
+ d.close()
}
- d := f.dirinfo
size := n
if size <= 0 {
diff --git a/src/os/dir_plan9.go b/src/os/dir_plan9.go
index 6ea5940e71df9fb58b6ce61fba086663cd33e60d..ab5c1efce5b075294c6964d64f812779b235ff4c 100644
--- a/src/os/dir_plan9.go
+++ b/src/os/dir_plan9.go
@@ -12,10 +12,14 @@ import (
func (file *File) readdir(n int, mode readdirMode) (names []string, dirents []DirEntry, infos []FileInfo, err error) {
// If this file has no dirinfo, create one.
- if file.dirinfo == nil {
- file.dirinfo = new(dirInfo)
+ d := file.dirinfo.Load()
+ if d == nil {
+ d = new(dirInfo)
+ file.dirinfo.Store(d)
}
- d := file.dirinfo
+ d.mu.Lock()
+ defer d.mu.Unlock()
+
size := n
if size <= 0 {
size = 100
diff --git a/src/os/dir_unix.go b/src/os/dir_unix.go
index e14edc13dc7089ad788cf1c15f47729485c469a7..7680be7799c0e6cd3e65ae34ad83f7a8c45c73dd 100644
--- a/src/os/dir_unix.go
+++ b/src/os/dir_unix.go
@@ -17,6 +17,7 @@ import (
// Auxiliary information if the File describes a directory
type dirInfo struct {
+ mu sync.Mutex
buf *[]byte // buffer for directory I/O
nbuf int // length of buf; return value from Getdirentries
bufp int // location of next record in buf.
@@ -43,13 +44,16 @@ func (d *dirInfo) close() {
}
func (f *File) readdir(n int, mode readdirMode) (names []string, dirents []DirEntry, infos []FileInfo, err error) {
- // If this file has no dirinfo, create one.
- if f.dirinfo == nil {
- f.dirinfo = new(dirInfo)
+ // If this file has no dirInfo, create one.
+ d := f.dirinfo.Load()
+ if d == nil {
+ d = new(dirInfo)
+ f.dirinfo.Store(d)
}
- d := f.dirinfo
+ d.mu.Lock()
+ defer d.mu.Unlock()
if d.buf == nil {
- f.dirinfo.buf = dirBufPool.Get().(*[]byte)
+ d.buf = dirBufPool.Get().(*[]byte)
}
// Change the meaning of n for the implementation below.
diff --git a/src/os/dir_windows.go b/src/os/dir_windows.go
index 0dbc3aec3e4ee9b8645c0515d7f0da5f09a5d7da..52d5acda2afd2188fa3a52e015df845f780a2f59 100644
--- a/src/os/dir_windows.go
+++ b/src/os/dir_windows.go
@@ -16,6 +16,7 @@ import (
// Auxiliary information if the File describes a directory
type dirInfo struct {
+ mu sync.Mutex
// buf is a slice pointer so the slice header
// does not escape to the heap when returning
// buf to dirBufPool.
@@ -93,14 +94,27 @@ func (d *dirInfo) init(h syscall.Handle) {
}
func (file *File) readdir(n int, mode readdirMode) (names []string, dirents []DirEntry, infos []FileInfo, err error) {
- if file.dirinfo == nil {
- file.dirinfo = new(dirInfo)
- file.dirinfo.init(file.pfd.Sysfd)
+ // If this file has no dirInfo, create one.
+ var d *dirInfo
+ for {
+ d = file.dirinfo.Load()
+ if d != nil {
+ break
+ }
+ d = new(dirInfo)
+ d.init(file.pfd.Sysfd)
+ if file.dirinfo.CompareAndSwap(nil, d) {
+ break
+ }
+ // We lost the race: try again.
+ d.close()
}
- d := file.dirinfo
+ d.mu.Lock()
+ defer d.mu.Unlock()
if d.buf == nil {
d.buf = dirBufPool.Get().(*[]byte)
}
+
wantAll := n <= 0
if wantAll {
n = -1
diff --git a/src/os/file.go b/src/os/file.go
index a41aac9bb387831201697f407ef1f3a91b59a190..ec8ad706607865da9f084fc41bbd77eebe3e8709 100644
--- a/src/os/file.go
+++ b/src/os/file.go
@@ -34,9 +34,13 @@
// }
// fmt.Printf("read %d bytes: %q\n", count, data[:count])
//
-// Note: The maximum number of concurrent operations on a File may be limited by
-// the OS or the system. The number should be high, but exceeding it may degrade
-// performance or cause other issues.
+// # Concurrency
+//
+// The methods of [File] correspond to file system operations. All are
+// safe for concurrent use. The maximum number of concurrent
+// operations on a File may be limited by the OS or the system. The
+// number should be high, but exceeding it may degrade performance or
+// cause other issues.
package os
import (
@@ -53,6 +57,8 @@ import (
)
// Name returns the name of the file as presented to Open.
+//
+// It is safe to call Name after [Close].
func (f *File) Name() string { return f.name }
// Stdin, Stdout, and Stderr are open Files pointing to the standard input,
@@ -279,7 +285,7 @@ func (f *File) Seek(offset int64, whence int) (ret int64, err error) {
return 0, err
}
r, e := f.seek(offset, whence)
- if e == nil && f.dirinfo != nil && r != 0 {
+ if e == nil && f.dirinfo.Load() != nil && r != 0 {
e = syscall.EISDIR
}
if e != nil {
diff --git a/src/os/file_plan9.go b/src/os/file_plan9.go
index 477674b80a95c81ce7bcf7335462822eab3b55ef..fc9c89f09a1aaf805dacdad0ba241db34ddcb6ea 100644
--- a/src/os/file_plan9.go
+++ b/src/os/file_plan9.go
@@ -9,6 +9,8 @@ import (
"internal/poll"
"io"
"runtime"
+ "sync"
+ "sync/atomic"
"syscall"
"time"
)
@@ -26,8 +28,8 @@ type file struct {
fdmu poll.FDMutex
fd int
name string
- dirinfo *dirInfo // nil unless directory being read
- appendMode bool // whether file is opened for appending
+ dirinfo atomic.Pointer[dirInfo] // nil unless directory being read
+ appendMode bool // whether file is opened for appending
}
// Fd returns the integer Plan 9 file descriptor referencing the open file.
@@ -60,6 +62,7 @@ func NewFile(fd uintptr, name string) *File {
// Auxiliary information if the File describes a directory
type dirInfo struct {
+ mu sync.Mutex
buf [syscall.STATMAX]byte // buffer for directory I/O
nbuf int // length of buf; return value from Read
bufp int // location of next record in buf.
@@ -349,11 +352,9 @@ func (f *File) seek(offset int64, whence int) (ret int64, err error) {
return 0, err
}
defer f.decref()
- if f.dirinfo != nil {
- // Free cached dirinfo, so we allocate a new one if we
- // access this file as a directory again. See #35767 and #37161.
- f.dirinfo = nil
- }
+ // Free cached dirinfo, so we allocate a new one if we
+ // access this file as a directory again. See #35767 and #37161.
+ f.dirinfo.Store(nil)
return syscall.Seek(f.fd, offset, whence)
}
diff --git a/src/os/file_unix.go b/src/os/file_unix.go
index f36028bfcbdaea9bd22dd5eada994481cdb991db..8ecbffa81f7b6a5ded1645f362d967d3c01055b0 100644
--- a/src/os/file_unix.go
+++ b/src/os/file_unix.go
@@ -11,6 +11,7 @@ import (
"internal/syscall/unix"
"io/fs"
"runtime"
+ "sync/atomic"
"syscall"
_ "unsafe" // for go:linkname
)
@@ -58,10 +59,10 @@ func rename(oldname, newname string) error {
type file struct {
pfd poll.FD
name string
- dirinfo *dirInfo // nil unless directory being read
- nonblock bool // whether we set nonblocking mode
- stdoutOrErr bool // whether this is stdout or stderr
- appendMode bool // whether file is opened for appending
+ dirinfo atomic.Pointer[dirInfo] // nil unless directory being read
+ nonblock bool // whether we set nonblocking mode
+ stdoutOrErr bool // whether this is stdout or stderr
+ appendMode bool // whether file is opened for appending
}
// Fd returns the integer Unix file descriptor referencing the open file.
@@ -325,9 +326,8 @@ func (file *file) close() error {
if file == nil {
return syscall.EINVAL
}
- if file.dirinfo != nil {
- file.dirinfo.close()
- file.dirinfo = nil
+ if info := file.dirinfo.Swap(nil); info != nil {
+ info.close()
}
var err error
if e := file.pfd.Close(); e != nil {
@@ -347,11 +347,10 @@ func (file *file) close() error {
// relative to the current offset, and 2 means relative to the end.
// It returns the new offset and an error, if any.
func (f *File) seek(offset int64, whence int) (ret int64, err error) {
- if f.dirinfo != nil {
+ if info := f.dirinfo.Swap(nil); info != nil {
// Free cached dirinfo, so we allocate a new one if we
// access this file as a directory again. See #35767 and #37161.
- f.dirinfo.close()
- f.dirinfo = nil
+ info.close()
}
ret, err = f.pfd.Seek(offset, whence)
runtime.KeepAlive(f)
diff --git a/src/os/file_windows.go b/src/os/file_windows.go
index 6ee15eb9932508495e441ecfceddeab8cf0e5b4e..d883eb5cb21e5680ebf324a5f66e69ee33d66e5a 100644
--- a/src/os/file_windows.go
+++ b/src/os/file_windows.go
@@ -11,6 +11,7 @@ import (
"internal/syscall/windows"
"runtime"
"sync"
+ "sync/atomic"
"syscall"
"unsafe"
)
@@ -25,8 +26,8 @@ const _UTIME_OMIT = -1
type file struct {
pfd poll.FD
name string
- dirinfo *dirInfo // nil unless directory being read
- appendMode bool // whether file is opened for appending
+ dirinfo atomic.Pointer[dirInfo] // nil unless directory being read
+ appendMode bool // whether file is opened for appending
}
// Fd returns the Windows handle referencing the open file.
@@ -127,9 +128,8 @@ func (file *file) close() error {
if file == nil {
return syscall.EINVAL
}
- if file.dirinfo != nil {
- file.dirinfo.close()
- file.dirinfo = nil
+ if info := file.dirinfo.Swap(nil); info != nil {
+ info.close()
}
var err error
if e := file.pfd.Close(); e != nil {
@@ -149,11 +149,10 @@ func (file *file) close() error {
// relative to the current offset, and 2 means relative to the end.
// It returns the new offset and an error, if any.
func (f *File) seek(offset int64, whence int) (ret int64, err error) {
- if f.dirinfo != nil {
+ if info := f.dirinfo.Swap(nil); info != nil {
// Free cached dirinfo, so we allocate a new one if we
// access this file as a directory again. See #35767 and #37161.
- f.dirinfo.close()
- f.dirinfo = nil
+ info.close()
}
ret, err = f.pfd.Seek(offset, whence)
runtime.KeepAlive(f)
diff --git a/src/os/types.go b/src/os/types.go
index 66eb8bc8cbfc6c5dd1e31c90197ef7bab4713463..d51a458f44f9fbff30cf25377e40f46591c55a19 100644
--- a/src/os/types.go
+++ b/src/os/types.go
@@ -13,6 +13,8 @@ import (
func Getpagesize() int { return syscall.Getpagesize() }
// File represents an open file descriptor.
+//
+// The methods of File are safe for concurrent use.
type File struct {
*file // os specific
}