1 files changed, 156 insertions, 0 deletions
diff --git a/src/runtime/sigqueue_plan9.go b/src/runtime/sigqueue_plan9.go
new file mode 100644
index 0000000..d5fe8f8
--- /dev/null
+++ b/src/runtime/sigqueue_plan9.go
@@ -0,0 +1,156 @@
+// Copyright 2009 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.
+
+// This file implements runtime support for signal handling.
+
+package runtime
+
+import _ "unsafe"
+
+const qsize = 64
+
+var sig struct {
+	q     noteQueue
+	inuse bool
+
+	lock     mutex
+	note     note
+	sleeping bool
+}
+
+type noteData struct {
+	s [_ERRMAX]byte
+	n int // n bytes of s are valid
+}
+
+type noteQueue struct {
+	lock mutex
+	data [qsize]noteData
+	ri   int
+	wi   int
+	full bool
+}
+
+// It is not allowed to allocate memory in the signal handler.
+func (q *noteQueue) push(item *byte) bool {
+	lock(&q.lock)
+	if q.full {
+		unlock(&q.lock)
+		return false
+	}
+	s := gostringnocopy(item)
+	copy(q.data[q.wi].s[:], s)
+	q.data[q.wi].n = len(s)
+	q.wi++
+	if q.wi == qsize {
+		q.wi = 0
+	}
+	if q.wi == q.ri {
+		q.full = true
+	}
+	unlock(&q.lock)
+	return true
+}
+
+func (q *noteQueue) pop() string {
+	lock(&q.lock)
+	q.full = false
+	if q.ri == q.wi {
+		unlock(&q.lock)
+		return ""
+	}
+	note := &q.data[q.ri]
+	item := string(note.s[:note.n])
+	q.ri++
+	if q.ri == qsize {
+		q.ri = 0
+	}
+	unlock(&q.lock)
+	return item
+}
+
+// Called from sighandler to send a signal back out of the signal handling thread.
+// Reports whether the signal was sent. If not, the caller typically crashes the program.
+func sendNote(s *byte) bool {
+	if !sig.inuse {
+		return false
+	}
+
+	// Add signal to outgoing queue.
+	if !sig.q.push(s) {
+		return false
+	}
+
+	lock(&sig.lock)
+	if sig.sleeping {
+		sig.sleeping = false
+		notewakeup(&sig.note)
+	}
+	unlock(&sig.lock)
+
+	return true
+}
+
+// Called to receive the next queued signal.
+// Must only be called from a single goroutine at a time.
+//go:linkname signal_recv os/signal.signal_recv
+func signal_recv() string {
+	for {
+		note := sig.q.pop()
+		if note != "" {
+			return note
+		}
+
+		lock(&sig.lock)
+		sig.sleeping = true
+		noteclear(&sig.note)
+		unlock(&sig.lock)
+		notetsleepg(&sig.note, -1)
+	}
+}
+
+// signalWaitUntilIdle waits until the signal delivery mechanism is idle.
+// This is used to ensure that we do not drop a signal notification due
+// to a race between disabling a signal and receiving a signal.
+// This assumes that signal delivery has already been disabled for
+// the signal(s) in question, and here we are just waiting to make sure
+// that all the signals have been delivered to the user channels
+// by the os/signal package.
+//go:linkname signalWaitUntilIdle os/signal.signalWaitUntilIdle
+func signalWaitUntilIdle() {
+	for {
+		lock(&sig.lock)
+		sleeping := sig.sleeping
+		unlock(&sig.lock)
+		if sleeping {
+			return
+		}
+		Gosched()
+	}
+}
+
+// Must only be called from a single goroutine at a time.
+//go:linkname signal_enable os/signal.signal_enable
+func signal_enable(s uint32) {
+	if !sig.inuse {
+		// This is the first call to signal_enable. Initialize.
+		sig.inuse = true // enable reception of signals; cannot disable
+		noteclear(&sig.note)
+	}
+}
+
+// Must only be called from a single goroutine at a time.
+//go:linkname signal_disable os/signal.signal_disable
+func signal_disable(s uint32) {
+}
+
+// Must only be called from a single goroutine at a time.
+//go:linkname signal_ignore os/signal.signal_ignore
+func signal_ignore(s uint32) {
+}
+
+//go:linkname signal_ignored os/signal.signal_ignored
+func signal_ignored(s uint32) bool {
+	return false
+}