From 5bbd4c2f1b9e45ebbdef29695d848a062b312fc7 Mon Sep 17 00:00:00 2001
From: Russ Cox <rsc@golang.org>
Date: Thu, 15 Oct 2009 17:46:53 -0700
Subject: [PATCH] publish semacquire and semrelease for use by sync.

more enforcing package boundaries

R=r
DELTA=46  (13 added, 15 deleted, 18 changed)
OCL=35806
CL=35806
---
 src/pkg/Make.deps             |  2 +-
 src/pkg/runtime/extern.go     | 11 +++++++++++
 src/pkg/runtime/sema.cgo      |  6 +++---
 src/pkg/sync/internal_test.go | 15 ---------------
 src/pkg/sync/mutex.go         | 21 +++++++++++----------
 src/pkg/sync/mutex_test.go    |  9 +++++----
 6 files changed, 31 insertions(+), 33 deletions(-)
 delete mode 100644 src/pkg/sync/internal_test.go

diff --git a/src/pkg/Make.deps b/src/pkg/Make.deps
index 21e412ba38..a90da1aba0 100644
--- a/src/pkg/Make.deps
+++ b/src/pkg/Make.deps
@@ -61,7 +61,7 @@ runtime.install:
 sort.install:
 strconv.install: bytes.install math.install os.install unicode.install utf8.install
 strings.install: os.install unicode.install utf8.install
-sync.install:
+sync.install: runtime.install
 syscall.install: sync.install
 tabwriter.install: bytes.install container/vector.install io.install os.install utf8.install
 template.install: bytes.install container/vector.install fmt.install io.install os.install reflect.install runtime.install strings.install
diff --git a/src/pkg/runtime/extern.go b/src/pkg/runtime/extern.go
index 131767aef1..70c6f434be 100644
--- a/src/pkg/runtime/extern.go
+++ b/src/pkg/runtime/extern.go
@@ -46,3 +46,14 @@ func GOMAXPROCS(n int)
 
 // Cgocalls returns the number of cgo calls made by the current process.
 func Cgocalls() int64
+
+// Semacquire waits until *s > 0 and then atomically decrements it.
+// It is intended as a simple sleep primitive for use by the synchronization
+// library and should not be used directly.
+func Semacquire(s *uint32)
+
+// Semrelease atomically increments *s and notifies a waiting goroutine
+// if one is blocked in Semacquire.
+// It is intended as a simple wakeup primitive for use by the synchronization
+// library and should not be used directly.
+func Semrelease(s *uint32)
diff --git a/src/pkg/runtime/sema.cgo b/src/pkg/runtime/sema.cgo
index 81834ae6dc..71395ce771 100644
--- a/src/pkg/runtime/sema.cgo
+++ b/src/pkg/runtime/sema.cgo
@@ -17,7 +17,7 @@
 // See Mullender and Cox, ``Semaphores in Plan 9,''
 // http://swtch.com/semaphore.pdf
 
-package sync
+package runtime
 #include "runtime.h"
 
 typedef struct Sema Sema;
@@ -176,10 +176,10 @@ semrelease(uint32 *addr)
 	semwakeup(addr);
 }
 
-func semacquire(addr *uint32) {
+func Semacquire(addr *uint32) {
 	semacquire(addr);
 }
 
-func semrelease(addr *uint32) {
+func Semrelease(addr *uint32) {
 	semrelease(addr);
 }
diff --git a/src/pkg/sync/internal_test.go b/src/pkg/sync/internal_test.go
deleted file mode 100644
index b365f79e91..0000000000
--- a/src/pkg/sync/internal_test.go
+++ /dev/null
@@ -1,15 +0,0 @@
-// 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.
-
-// expose internals for testing
-
-package sync
-
-func Semacquire(s *int32) {
-	semacquire(s);
-}
-
-func Semrelease(s *int32) {
-	semrelease(s);
-}
diff --git a/src/pkg/sync/mutex.go b/src/pkg/sync/mutex.go
index 23691aa33e..309970f1e5 100644
--- a/src/pkg/sync/mutex.go
+++ b/src/pkg/sync/mutex.go
@@ -8,23 +8,24 @@
 // is better done via channels and communication.
 package sync
 
-func cas(val *int32, old, new int32) bool
-func semacquire(*int32)
-func semrelease(*int32)
+import "runtime"
+
+func cas(val *uint32, old, new uint32) bool
 
 // A Mutex is a mutual exclusion lock.
 // Mutexes can be created as part of other structures;
 // the zero value for a Mutex is an unlocked mutex.
 type Mutex struct {
-	key	int32;
-	sema	int32;
+	key	uint32;
+	sema	uint32;
 }
 
-func xadd(val *int32, delta int32) (new int32) {
+func xadd(val *uint32, delta int32) (new uint32) {
 	for {
 		v := *val;
-		if cas(val, v, v+delta) {
-			return v+delta;
+		nv := v+uint32(delta);
+		if cas(val, v, nv) {
+			return nv;
 		}
 	}
 	panic("unreached");
@@ -38,7 +39,7 @@ func (m *Mutex) Lock() {
 		// changed from 0 to 1; we hold lock
 		return;
 	}
-	semacquire(&m.sema);
+	runtime.Semacquire(&m.sema);
 }
 
 // Unlock unlocks m.
@@ -52,7 +53,7 @@ func (m *Mutex) Unlock() {
 		// changed from 1 to 0; no contention
 		return;
 	}
-	semrelease(&m.sema);
+	runtime.Semrelease(&m.sema);
 }
 
 // Stub implementation of r/w locks.
diff --git a/src/pkg/sync/mutex_test.go b/src/pkg/sync/mutex_test.go
index 2944a20fb9..d7be79fff2 100644
--- a/src/pkg/sync/mutex_test.go
+++ b/src/pkg/sync/mutex_test.go
@@ -7,20 +7,21 @@
 package sync_test
 
 import (
+		"runtime";
 	.	"sync";
 		"testing";
 )
 
-func HammerSemaphore(s *int32, cdone chan bool) {
+func HammerSemaphore(s *uint32, cdone chan bool) {
 	for i := 0; i < 1000; i++ {
-		Semacquire(s);
-		Semrelease(s);
+		runtime.Semacquire(s);
+		runtime.Semrelease(s);
 	}
 	cdone <- true;
 }
 
 func TestSemaphore(t *testing.T) {
-	s := new(int32);
+	s := new(uint32);
 	*s = 1;
 	c := make(chan bool);
 	for i := 0; i < 10; i++ {
-- 
2.50.0