os: revert the use of AddCleanup to close files and roots

This reverts commit fdaac84480b02e600660d0ca7c15339138807107.

Updates #70907
Updates #74574
Updates #74642

Reason for revert: Issue #74574

Change-Id: I7b55b85736e4210d9b6f3fd7a24050ac7bdefef9
Reviewed-on: https://go-review.googlesource.com/c/go/+/688435
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>

1 files changed, 4 insertions, 6 deletions

diff --git a/src/os/file_plan9.go b/src/os/file_plan9.go
index 656a3e0bb0..17026409eb 100644
--- a/src/os/file_plan9.go
+++ b/src/os/file_plan9.go
@@ -23,7 +23,7 @@ func fixLongPath(path string) string {
 
 // file is the real representation of *File.
 // The extra level of indirection ensures that no clients of os
-// can overwrite this data, which could cause the cleanup
+// can overwrite this data, which could cause the finalizer
 // to close the wrong file descriptor.
 type file struct {
 	fdmu       poll.FDMutex
@@ -31,7 +31,6 @@ type file struct {
 	name       string
 	dirinfo    atomic.Pointer[dirInfo] // nil unless directory being read
 	appendMode bool                    // whether file is opened for appending
-	cleanup    runtime.Cleanup         // cleanup closes the file when no longer referenced
 }
 
 // fd is the Plan 9 implementation of Fd.
@@ -49,7 +48,7 @@ func newFileFromNewFile(fd uintptr, name string) *File {
 		return nil
 	}
 	f := &File{&file{sysfd: fdi, name: name}}
-	f.cleanup = runtime.AddCleanup(f, func(f *file) { f.close() }, f.file)
+	runtime.SetFinalizer(f.file, (*file).close)
 	return f
 }
 
@@ -160,9 +159,8 @@ func (file *file) close() error {
 
 	err := file.decref()
 
-	// There is no need for a cleanup at this point. File must be alive at the point
-	// where cleanup.stop is called.
-	file.cleanup.Stop()
+	// no need for a finalizer anymore
+	runtime.SetFinalizer(file, nil)
 	return err
 }