internal/poll: defer IOCP association until first IO operation

Defer the association of the IOCP to the handle until the first
I/O operation is performed.

A handle can only be associated with one IOCP at a time, so this allows
external code to associate the handle with their own IOCP and still be
able to use a FD (through os.NewFile) to pass the handle around
(e.g. to a child process standard input, output, and error) without
having to worry about the IOCP association.

This CL doesn't change any user-visible behavior, as os.NewFile still
initializes the FD as non-pollable.

For #19098.

Change-Id: Id22a49846d4fda3a66ffcc0bc1b48eb39b395dc5
Reviewed-on: https://go-review.googlesource.com/c/go/+/661955
Reviewed-by: Damien Neil <[email protected]>
Reviewed-by: Carlos Amedee <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>

Author: qmuntal

src/internal/poll/fd_plan9.go

@@ -36,6 +36,10 @@ type FD struct {
 	isFile bool
 }
 
+func (fd *FD) initIO() error {
+	return nil
+}
+
 // We need this to close out a file descriptor when it is unlocked,
 // but the real implementation has to live in the net package because
 // it uses os.File's.

src/internal/poll/fd_poll_runtime.go

@@ -155,6 +155,8 @@ func setDeadlineImpl(fd *FD, t time.Time, mode int) error {
 		return err
 	}
 	defer fd.decref()
+
+	fd.initIO()
 	if fd.pd.runtimeCtx == 0 {
 		return ErrNoDeadline
 	}

src/internal/poll/fd_unix.go

@@ -47,6 +47,10 @@ type FD struct {
 	isFile bool
 }
 
+func (fd *FD) initIO() error {
+	return nil
+}
+
 // Init initializes the FD. The Sysfd field should already be set.
 // This can be called multiple times on a single FD.
 // The net argument is a network name from the net package (e.g., "tcp"),

src/internal/poll/fd_windows.go

@@ -157,6 +157,7 @@ func (o *operation) InitMsg(p []byte, oob []byte) {
 // It supports both synchronous and asynchronous IO.
 func execIO(o *operation, submit func(o *operation) error) (int, error) {
 	fd := o.fd
+	fd.initIO()
 	// Notify runtime netpoll about starting IO.
 	err := fd.pd.prepare(int(o.mode), fd.isFile)
 	if err != nil {
@@ -297,8 +298,13 @@ type FD struct {
 	// The kind of this file.
 	kind fileKind
 
-	// Whether FILE_FLAG_OVERLAPPED was not set when opening the file
+	// Whether FILE_FLAG_OVERLAPPED was not set when opening the file.
 	isBlocking bool
+
+	// Initialization parameters.
+	initIOOnce   sync.Once
+	initIOErr    error // only used in the net package
+	initPollable bool  // value passed to [FD.Init]
 }
 
 // setOffset sets the offset fields of the overlapped object
@@ -336,7 +342,51 @@ const (
 )
 
 // logInitFD is set by tests to enable file descriptor initialization logging.
-var logInitFD func(net string, fd *FD, err error)
+var logInitFD func(net int, fd *FD, err error)
+
+func (fd *FD) initIO() error {
+	fd.initIOOnce.Do(func() {
+		if fd.initPollable {
+			// The runtime poller will ignore I/O completion
+			// notifications not initiated by this package,
+			// so it is safe to add handles owned by the caller.
+			//
+			// If we could not add the handle to the runtime poller,
+			// assume the handle hasn't been opened for overlapped I/O.
+			fd.initIOErr = fd.pd.init(fd)
+			if fd.initIOErr != nil {
+				fd.initPollable = false
+			}
+		}
+		if logInitFD != nil {
+			logInitFD(int(fd.kind), fd, fd.initIOErr)
+		}
+		if !fd.initPollable {
+			// Handle opened for overlapped I/O (aka non-blocking) that are not added
+			// to the runtime poller need special handling when reading and writing.
+			var info windows.FILE_MODE_INFORMATION
+			if err := windows.NtQueryInformationFile(fd.Sysfd, &windows.IO_STATUS_BLOCK{}, uintptr(unsafe.Pointer(&info)), uint32(unsafe.Sizeof(info)), windows.FileModeInformation); err == nil {
+				fd.isBlocking = info.Mode&(windows.FILE_SYNCHRONOUS_IO_ALERT|windows.FILE_SYNCHRONOUS_IO_NONALERT) != 0
+			} else {
+				// If we fail to get the file mode information, assume the file is blocking.
+				fd.isBlocking = true
+			}
+		} else {
+			fd.rop.runtimeCtx = fd.pd.runtimeCtx
+			fd.wop.runtimeCtx = fd.pd.runtimeCtx
+			if fd.kind != kindNet || socketCanUseSetFileCompletionNotificationModes {
+				// Non-socket handles can use SetFileCompletionNotificationModes without problems.
+				err := syscall.SetFileCompletionNotificationModes(fd.Sysfd,
+					syscall.FILE_SKIP_SET_EVENT_ON_HANDLE|syscall.FILE_SKIP_COMPLETION_PORT_ON_SUCCESS,
+				)
+				if err == nil {
+					fd.skipSyncNotif = true
+				}
+			}
+		}
+	})
+	return fd.initIOErr
+}
 
 // Init initializes the FD. The Sysfd field should already be set.
 // This can be called multiple times on a single FD.
@@ -349,63 +399,42 @@ func (fd *FD) Init(net string, pollable bool) error {
 	}
 
 	switch net {
-	case "file", "dir":
+	case "file":
 		fd.kind = kindFile
 	case "console":
 		fd.kind = kindConsole
 	case "pipe":
 		fd.kind = kindPipe
-	case "tcp", "tcp4", "tcp6",
-		"udp", "udp4", "udp6",
-		"ip", "ip4", "ip6",
-		"unix", "unixgram", "unixpacket":
-		fd.kind = kindNet
 	default:
-		return errors.New("internal error: unknown network type " + net)
+		// We don't actually care about the various network types.
+		fd.kind = kindNet
 	}
 	fd.isFile = fd.kind != kindNet
+	fd.initPollable = pollable
 	fd.rop.mode = 'r'
 	fd.wop.mode = 'w'
 	fd.rop.fd = fd
 	fd.wop.fd = fd
 
-	var err error
-	if pollable {
-		// Note that the runtime poller will ignore I/O completion
-		// notifications not initiated by this package,
-		// so it is safe to add handles owned by the caller.
-		//
-		// If we could not add the handle to the runtime poller,
-		// assume the handle hasn't been opened for overlapped I/O.
-		err = fd.pd.init(fd)
-		pollable = err == nil
-	}
-	if logInitFD != nil {
-		logInitFD(net, fd, err)
-	}
-	if !pollable {
-		// Handle opened for overlapped I/O (aka non-blocking) that are not added
-		// to the runtime poller need special handling when reading and writing.
-		var info windows.FILE_MODE_INFORMATION
-		if err := windows.NtQueryInformationFile(fd.Sysfd, &windows.IO_STATUS_BLOCK{}, uintptr(unsafe.Pointer(&info)), uint32(unsafe.Sizeof(info)), windows.FileModeInformation); err == nil {
-			fd.isBlocking = info.Mode&(windows.FILE_SYNCHRONOUS_IO_ALERT|windows.FILE_SYNCHRONOUS_IO_NONALERT) != 0
-		} else {
-			// If we fail to get the file mode information, assume the file is blocking.
-			fd.isBlocking = true
-		}
-		return err
-	}
-	if fd.kind != kindNet || socketCanUseSetFileCompletionNotificationModes {
-		// Non-socket handles can use SetFileCompletionNotificationModes without problems.
-		err := syscall.SetFileCompletionNotificationModes(fd.Sysfd,
-			syscall.FILE_SKIP_SET_EVENT_ON_HANDLE|syscall.FILE_SKIP_COMPLETION_PORT_ON_SUCCESS,
-		)
-		if err == nil {
-			fd.skipSyncNotif = true
+	// A file handle (and its duplicated handles) can only be associated
+	// with one IOCP. A new association will fail if the handle is already
+	// associated. Defer the association until the first I/O operation so that
+	// overlapped handles passed in os.NewFile have a chance to be used
+	// with an external IOCP. This is common case, for example, when calling
+	// os.NewFile on a handle just to pass it to a exec.Command standard
+	// input/output/error. If the association fails, the I/O operations
+	// will be performed synchronously.
+	if fd.kind == kindNet {
+		// The net package is the only consumer that requires overlapped
+		// handles and that cares about handle IOCP association errors.
+		// We can should do the IOCP association here.
+		return fd.initIO()
+	} else {
+		if logInitFD != nil {
+			// For testing.
+			logInitFD(int(fd.kind), fd, nil)
 		}
 	}
-	fd.rop.runtimeCtx = fd.pd.runtimeCtx
-	fd.wop.runtimeCtx = fd.pd.runtimeCtx
 	return nil
 }
 

src/internal/poll/fd_windows_test.go

@@ -23,7 +23,7 @@ import (
 )
 
 type loggedFD struct {
-	Net string
+	Net int
 	FD  *poll.FD
 	Err error
 }
@@ -33,7 +33,7 @@ var (
 	loggedFDs map[syscall.Handle]*loggedFD
 )
 
-func logFD(net string, fd *poll.FD, err error) {
+func logFD(net int, fd *poll.FD, err error) {
 	logMu.Lock()
 	defer logMu.Unlock()
 
@@ -201,10 +201,6 @@ func newFD(t testing.TB, h syscall.Handle, kind string, overlapped, pollable boo
 	if overlapped && err != nil {
 		// Overlapped file handles should not error.
 		t.Fatal(err)
-	} else if !overlapped && pollable && err == nil {
-		// Non-overlapped file handles should return an error but still
-		// be usable as sync handles.
-		t.Fatal("expected error for non-overlapped file handle")
 	}
 	return &fd
 }
@@ -454,6 +450,24 @@ func TestPipeWriteEOF(t *testing.T) {
 	}
 }
 
+func TestPipeReadTimeout(t *testing.T) {
+	t.Parallel()
+	name := pipeName()
+	_ = newBytePipe(t, name, true, true)
+	file := newFile(t, name, true, true)
+
+	err := file.SetReadDeadline(time.Now().Add(time.Millisecond))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var buf [10]byte
+	_, err = file.Read(buf[:])
+	if err != poll.ErrDeadlineExceeded {
+		t.Errorf("expected deadline exceeded, got %v", err)
+	}
+}
+
 func TestPipeCanceled(t *testing.T) {
 	t.Parallel()
 	name := pipeName()
@@ -488,6 +502,26 @@ func TestPipeCanceled(t *testing.T) {
 	}
 }
 
+func TestPipeExternalIOCP(t *testing.T) {
+	// Test that a caller can associate an overlapped handle to an external IOCP
+	// even when the handle is also associated to a poll.FD. Also test that
+	// the FD can still perform I/O after the association.
+	t.Parallel()
+	name := pipeName()
+	pipe := newMessagePipe(t, name, true, true)
+	_ = newFile(t, name, true, true) // Just open a pipe client
+
+	_, err := windows.CreateIoCompletionPort(syscall.Handle(pipe.Sysfd), 0, 0, 1)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	_, err = pipe.Write([]byte("hello"))
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
 func BenchmarkReadOverlapped(b *testing.B) {
 	benchmarkRead(b, true)
 }

src/internal/syscall/windows/syscall_windows.go

@@ -513,6 +513,7 @@ const (
 	PIPE_TYPE_MESSAGE = 0x00000004
 )
 
+//sys	CreateIoCompletionPort(filehandle syscall.Handle, cphandle syscall.Handle, key uintptr, threadcnt uint32) (handle syscall.Handle, err error)
 //sys	GetOverlappedResult(handle syscall.Handle, overlapped *syscall.Overlapped, done *uint32, wait bool) (err error)
 //sys	CreateNamedPipe(name *uint16, flags uint32, pipeMode uint32, maxInstances uint32, outSize uint32, inSize uint32, defaultTimeout uint32, sa *syscall.SecurityAttributes) (handle syscall.Handle, err error)  [failretval==syscall.InvalidHandle] = CreateNamedPipeW