5 files changed, 274 insertions, 0 deletions
diff --git a/src/pkg/sync/Makefile b/src/pkg/sync/Makefile
new file mode 100644
index 000000000..566853d57
--- /dev/null
+++ b/src/pkg/sync/Makefile
@@ -0,0 +1,61 @@
+# 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.
+
+# DO NOT EDIT.  Automatically generated by gobuild.
+# gobuild -m asm_${GOARCH}.s mutex.go >Makefile
+
+D=
+
+include $(GOROOT)/src/Make.$(GOARCH)
+AR=gopack
+
+default: packages
+
+clean:
+	rm -rf *.[$(OS)] *.a [$(OS)].out _obj
+
+test: packages
+	gotest
+
+coverage: packages
+	gotest
+	6cov -g `pwd` | grep -v '_test\.go:'
+
+%.$O: %.go
+	$(GC) -I_obj $*.go
+
+%.$O: %.c
+	$(CC) $*.c
+
+%.$O: %.s
+	$(AS) $*.s
+
+O1=\
+	asm_$(GOARCH).$O\
+	mutex.$O\
+
+
+phases: a1
+_obj$D/sync.a: phases
+
+a1: $(O1)
+	$(AR) grc _obj$D/sync.a asm_$(GOARCH).$O mutex.$O
+	rm -f $(O1)
+
+
+newpkg: clean
+	mkdir -p _obj$D
+	$(AR) grc _obj$D/sync.a
+
+$(O1): newpkg
+$(O2): a1
+
+nuke: clean
+	rm -f $(GOROOT)/pkg/$(GOOS)_$(GOARCH)$D/sync.a
+
+packages: _obj$D/sync.a
+
+install: packages
+	test -d $(GOROOT)/pkg && mkdir -p $(GOROOT)/pkg/$(GOOS)_$(GOARCH)$D
+	cp _obj$D/sync.a $(GOROOT)/pkg/$(GOOS)_$(GOARCH)$D/sync.a
diff --git a/src/pkg/sync/asm_386.s b/src/pkg/sync/asm_386.s
new file mode 100644
index 000000000..f71182b75
--- /dev/null
+++ b/src/pkg/sync/asm_386.s
@@ -0,0 +1,23 @@
+// 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.
+
+// func cas(val *int32, old, new int32) bool
+// Atomically:
+//	if *val == old {
+//		*val = new;
+//		return true;
+//	}else
+//		return false;
+TEXT sync·cas(SB), 7, $0
+	MOVL	4(SP), BX
+	MOVL	8(SP), AX
+	MOVL	12(SP), CX
+	LOCK
+	CMPXCHGL	CX, 0(BX)
+	JZ ok
+	MOVL	$0, 16(SP)
+	RET
+ok:
+	MOVL	$1, 16(SP)
+	RET
diff --git a/src/pkg/sync/asm_amd64.s b/src/pkg/sync/asm_amd64.s
new file mode 100644
index 000000000..07389dd3b
--- /dev/null
+++ b/src/pkg/sync/asm_amd64.s
@@ -0,0 +1,23 @@
+// 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.
+
+// func cas(val *int32, old, new int32) bool
+// Atomically:
+//	if *val == old {
+//		*val = new;
+//		return true;
+//	}else
+//		return false;
+TEXT sync·cas(SB), 7, $0
+	MOVQ	8(SP), BX
+	MOVL	16(SP), AX
+	MOVL	20(SP), CX
+	LOCK
+	CMPXCHGL	CX, 0(BX)
+	JZ ok
+	MOVL	$0, 24(SP)
+	RET
+ok:
+	MOVL	$1, 24(SP)
+	RET
diff --git a/src/pkg/sync/mutex.go b/src/pkg/sync/mutex.go
new file mode 100644
index 000000000..5a6311a83
--- /dev/null
+++ b/src/pkg/sync/mutex.go
@@ -0,0 +1,114 @@
+// 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.
+
+// The sync package provides basic synchronization primitives
+// such as mutual exclusion locks.  These are intended for use
+// by low-level library routines.  Higher-level synchronization
+// is better done via channels and communication.
+package sync
+
+func cas(val *int32, old, new int32) bool
+func semacquire(*int32)
+func semrelease(*int32)
+
+// 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;
+}
+
+func xadd(val *int32, delta int32) (new int32) {
+	for {
+		v := *val;
+		if cas(val, v, v+delta) {
+			return v+delta;
+		}
+	}
+	panic("unreached")
+}
+
+// Lock locks m.
+// If the lock is already in use, the calling goroutine
+// blocks until the mutex is available.
+func (m *Mutex) Lock() {
+	if xadd(&m.key, 1) == 1 {
+		// changed from 0 to 1; we hold lock
+		return;
+	}
+	semacquire(&m.sema);
+}
+
+// Unlock unlocks m.
+// It is a run-time error if m is not locked on entry to Unlock.
+//
+// A locked Mutex is not associated with a particular goroutine.
+// It is allowed for one goroutine to lock a Mutex and then
+// arrange for another goroutine to unlock it.
+func (m *Mutex) Unlock() {
+	if xadd(&m.key, -1) == 0 {
+		// changed from 1 to 0; no contention
+		return;
+	}
+	semrelease(&m.sema);
+}
+
+// Stub implementation of r/w locks.
+// This satisfies the semantics but
+// is not terribly efficient.
+
+// The next comment goes in the BUGS section of the document,
+// in its own paragraph, without the (rsc) tag.
+
+// BUG(rsc): RWMutex does not (yet) allow multiple readers;
+// instead it behaves as if RLock and RUnlock were Lock and Unlock.
+
+// An RWMutex is a reader/writer mutual exclusion lock.
+// The lock can be held by an arbitrary number of readers
+// or a single writer.
+// RWMutexes can be created as part of other
+// structures; the zero value for a RWMutex is
+// an unlocked mutex.
+type RWMutex struct {
+	m Mutex;
+}
+
+// RLock locks rw for reading.
+// If the lock is already locked for writing or there is a writer already waiting
+// to acquire the lock, RLock blocks until the writer has released the lock.
+func (rw *RWMutex) RLock() {
+	rw.m.Lock();
+}
+
+// RUnlock undoes a single RLock call;
+// it does not affect other simultaneous readers.
+// It is a run-time error if rw is not locked for reading
+// on entry to RUnlock.
+func (rw *RWMutex) RUnlock() {
+	rw.m.Unlock();
+}
+
+// Lock locks rw for writing.
+// If the lock is already locked for reading or writing,
+// Lock blocks until the lock is available.
+// To ensure that the lock eventually becomes available,
+// a blocked Lock call excludes new readers from acquiring
+// the lock.
+func (rw *RWMutex) Lock() {
+	rw.m.Lock();
+}
+
+// Unlock unlocks rw for writing.
+// It is a run-time error if rw is not locked for writing
+// on entry to Unlock.
+//
+// Like for Mutexes,
+// a locked RWMutex is not associated with a particular goroutine.
+// It is allowed for one goroutine to RLock (Lock) an RWMutex and then
+// arrange for another goroutine to RUnlock (Unlock) it.
+func (rw *RWMutex) Unlock() {
+	rw.m.Unlock();
+}
+
diff --git a/src/pkg/sync/mutex_test.go b/src/pkg/sync/mutex_test.go
new file mode 100644
index 000000000..819dbb9de
--- /dev/null
+++ b/src/pkg/sync/mutex_test.go
@@ -0,0 +1,53 @@
+// 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.
+
+// GOMAXPROCS=10 gotest
+
+package sync
+
+import (
+	"sync";
+	"testing"
+)
+
+func HammerSemaphore(s *int32, cdone chan bool) {
+	for i := 0; i < 1000; i++ {
+		semacquire(s);
+		semrelease(s);
+	}
+	cdone <- true;
+}
+
+func TestSemaphore(t *testing.T) {
+	s := new(int32);
+	*s = 1;
+	c := make(chan bool);
+	for i := 0; i < 10; i++ {
+		go HammerSemaphore(s, c);
+	}
+	for i := 0; i < 10; i++ {
+		<-c;
+	}
+}
+
+
+func HammerMutex(m *Mutex, cdone chan bool) {
+	for i := 0; i < 1000; i++ {
+		m.Lock();
+		m.Unlock();
+	}
+	cdone <- true;
+}
+
+func TestMutex(t *testing.T) {
+	m := new(Mutex);
+	c := make(chan bool);
+	for i := 0; i < 10; i++ {
+		go HammerMutex(m, c);
+	}
+	for i := 0; i < 10; i++ {
+		<-c;
+	}
+}
+