os: add and use ignoringEINTR2

Copy ignoringEINTR2 from internal/poll and make use of it to remove
open-coded implementations.

Change-Id: I8802862f2012980f2af445b75eb45bb5a97bcc2a
Reviewed-on: https://go-review.googlesource.com/c/go/+/627479
Auto-Submit: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Damien Neil <dneil@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

src/os/file_plan9.go

@@ -617,3 +617,7 @@ func newRawConn(file *File) (*rawConn, error) {
 func ignoringEINTR(fn func() error) error {
 	return fn()
 }
+
+func ignoringEINTR2[T any](fn func() (T, error)) (T, error) {
+	return fn()
+}

src/os/file_posix.go

@@ -254,3 +254,13 @@ func ignoringEINTR(fn func() error) error {
 		}
 	}
 }
+
+// ignoringEINTR2 is ignoringEINTR, but returning an additional value.
+func ignoringEINTR2[T any](fn func() (T, error)) (T, error) {
+	for {
+		v, err := fn()
+		if err != syscall.EINTR {
+			return v, err
+		}
+	}
+}

src/os/file_unix.go

@@ -446,22 +446,15 @@ func Symlink(oldname, newname string) error {
 func readlink(name string) (string, error) {
 	for len := 128; ; len *= 2 {
 		b := make([]byte, len)
-		var (
+		n, err := ignoringEINTR2(func() (int, error) {
-			n int
+			return fixCount(syscall.Readlink(name, b))
-			e error
+		})
-		)
-		for {
-			n, e = fixCount(syscall.Readlink(name, b))
-			if e != syscall.EINTR {
-				break
-			}
-		}
 		// buffer too small
-		if (runtime.GOOS == "aix" || runtime.GOOS == "wasip1") && e == syscall.ERANGE {
+		if (runtime.GOOS == "aix" || runtime.GOOS == "wasip1") && err == syscall.ERANGE {
 			continue
 		}
-		if e != nil {
+		if err != nil {
-			return "", &PathError{Op: "readlink", Path: name, Err: e}
+			return "", &PathError{Op: "readlink", Path: name, Err: err}
 		}
 		if n < len {
 			return string(b[0:n]), nil

src/os/getwd.go

@@ -53,12 +53,7 @@ func Getwd() (dir string, err error) {
 
 	// If the operating system provides a Getwd call, use it.
 	if syscall.ImplementsGetwd {
-		for {
+		dir, err = ignoringEINTR2(syscall.Getwd)
-			dir, err = syscall.Getwd()
-			if err != syscall.EINTR {
-				break
-			}
-		}
 		// Linux returns ENAMETOOLONG if the result is too long.
 		// Some BSD systems appear to return EINVAL.
 		// FreeBSD systems appear to use ENOMEM

src/os/removeall_at.go

@@ -166,20 +166,11 @@ func removeAllFrom(parent *File, base string) error {
 // we are going to (try to) remove the file.
 // The contents of this file are not relevant for test caching.
 func openDirAt(dirfd int, name string) (*File, error) {
-	var r int
+	r, err := ignoringEINTR2(func() (int, error) {
-	for {
+		return unix.Openat(dirfd, name, O_RDONLY|syscall.O_CLOEXEC|syscall.O_DIRECTORY|syscall.O_NOFOLLOW, 0)
-		var e error
+	})
-		r, e = unix.Openat(dirfd, name, O_RDONLY|syscall.O_CLOEXEC|syscall.O_DIRECTORY|syscall.O_NOFOLLOW, 0)
+	if err != nil {
-		if e == nil {
+		return nil, err
-			break
-		}
-
-		// See comment in openFileNolog.
-		if e == syscall.EINTR {
-			continue
-		}
-
-		return nil, e
 	}
 
 	if !supportsCloseOnExec {