1 files changed, 42 insertions, 0 deletions
diff --git a/src/internal/poll/file_plan9.go b/src/internal/poll/file_plan9.go
new file mode 100644
index 0000000..57dc0c6
--- /dev/null
+++ b/src/internal/poll/file_plan9.go
@@ -0,0 +1,42 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package poll
+
+// Expose fdMutex for use by the os package on Plan 9.
+// On Plan 9 we don't want to use async I/O for file operations,
+// but we still want the locking semantics that fdMutex provides.
+
+// FDMutex is an exported fdMutex, only for Plan 9.
+type FDMutex struct {
+	fdmu fdMutex
+}
+
+func (fdmu *FDMutex) Incref() bool {
+	return fdmu.fdmu.incref()
+}
+
+func (fdmu *FDMutex) Decref() bool {
+	return fdmu.fdmu.decref()
+}
+
+func (fdmu *FDMutex) IncrefAndClose() bool {
+	return fdmu.fdmu.increfAndClose()
+}
+
+func (fdmu *FDMutex) ReadLock() bool {
+	return fdmu.fdmu.rwlock(true)
+}
+
+func (fdmu *FDMutex) ReadUnlock() bool {
+	return fdmu.fdmu.rwunlock(true)
+}
+
+func (fdmu *FDMutex) WriteLock() bool {
+	return fdmu.fdmu.rwlock(false)
+}
+
+func (fdmu *FDMutex) WriteUnlock() bool {
+	return fdmu.fdmu.rwunlock(false)
+}