libgo: Update to weekly.2012-02-22 release.

From-SVN: r184819

9 files changed, 182 insertions, 30 deletions

diff --git a/libgo/go/sync/cond.go b/libgo/go/sync/cond.go
index 75494b5..1fc3dea 100644
--- a/libgo/go/sync/cond.go
+++ b/libgo/go/sync/cond.go
@@ -4,8 +4,6 @@
 
 package sync
 
-import "runtime"
-
 // Cond implements a condition variable, a rendezvous point
 // for goroutines waiting for or announcing the occurrence
 // of an event.
@@ -43,9 +41,10 @@ func NewCond(l Locker) *Cond {
 
 // Wait atomically unlocks c.L and suspends execution
 // of the calling goroutine.  After later resuming execution,
-// Wait locks c.L before returning.
+// Wait locks c.L before returning.  Unlike in other systems,
+// Wait cannot return unless awoken by Broadcast or Signal.
 //
-// Because L is not locked when Wait first resumes, the caller
+// Because c.L is not locked when Wait first resumes, the caller
 // typically cannot assume that the condition is true when
 // Wait returns.  Instead, the caller should Wait in a loop:
 //
@@ -65,7 +64,7 @@ func (c *Cond) Wait() {
 	c.newWaiters++
 	c.m.Unlock()
 	c.L.Unlock()
-	runtime.Semacquire(s)
+	runtime_Semacquire(s)
 	c.L.Lock()
 }
 
@@ -84,7 +83,7 @@ func (c *Cond) Signal() {
 	}
 	if c.oldWaiters > 0 {
 		c.oldWaiters--
-		runtime.Semrelease(c.oldSema)
+		runtime_Semrelease(c.oldSema)
 	}
 	c.m.Unlock()
 }
@@ -98,13 +97,13 @@ func (c *Cond) Broadcast() {
 	// Wake both generations.
 	if c.oldWaiters > 0 {
 		for i := 0; i < c.oldWaiters; i++ {
-			runtime.Semrelease(c.oldSema)
+			runtime_Semrelease(c.oldSema)
 		}
 		c.oldWaiters = 0
 	}
 	if c.newWaiters > 0 {
 		for i := 0; i < c.newWaiters; i++ {
-			runtime.Semrelease(c.newSema)
+			runtime_Semrelease(c.newSema)
 		}
 		c.newWaiters = 0
 		c.newSema = nil
diff --git a/libgo/go/sync/example_test.go b/libgo/go/sync/example_test.go
new file mode 100644
index 0000000..1424b1e
--- /dev/null
+++ b/libgo/go/sync/example_test.go
@@ -0,0 +1,34 @@
+// Copyright 2012 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 sync_test
+
+import (
+	"net/http"
+	"sync"
+)
+
+// This example fetches several URLs concurrently,
+// using a WaitGroup to block until all the fetches are complete.
+func ExampleWaitGroup() {
+	var wg sync.WaitGroup
+	var urls = []string{
+		"http://www.golang.org/",
+		"http://www.google.com/",
+		"http://www.somestupidname.com/",
+	}
+	for _, url := range urls {
+		// Increment the WaitGroup counter.
+		wg.Add(1)
+		// Launch a goroutine to fetch the URL.
+		go func(url string) {
+			// Fetch the URL.
+			http.Get(url)
+			// Decrement the counter.
+			wg.Done()
+		}(url)
+	}
+	// Wait for all HTTP fetches to complete.
+	wg.Wait()
+}
diff --git a/libgo/go/sync/export_test.go b/libgo/go/sync/export_test.go
new file mode 100644
index 0000000..fa5983a
--- /dev/null
+++ b/libgo/go/sync/export_test.go
@@ -0,0 +1,9 @@
+// Copyright 2012 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 sync
+
+// Export for testing.
+var Runtime_Semacquire = runtime_Semacquire
+var Runtime_Semrelease = runtime_Semrelease
diff --git a/libgo/go/sync/mutex.go b/libgo/go/sync/mutex.go
index 4fc0274..9494cc3 100644
--- a/libgo/go/sync/mutex.go
+++ b/libgo/go/sync/mutex.go
@@ -10,10 +10,7 @@
 // Values containing the types defined in this package should not be copied.
 package sync
 
-import (
-	"runtime"
-	"sync/atomic"
-)
+import "sync/atomic"
 
 // A Mutex is a mutual exclusion lock.
 // Mutexes can be created as part of other structures;
@@ -60,7 +57,7 @@ func (m *Mutex) Lock() {
 			if old&mutexLocked == 0 {
 				break
 			}
-			runtime.Semacquire(&m.sema)
+			runtime_Semacquire(&m.sema)
 			awoke = true
 		}
 	}
@@ -89,7 +86,7 @@ func (m *Mutex) Unlock() {
 		// Grab the right to wake someone.
 		new = (old - 1<<mutexWaiterShift) | mutexWoken
 		if atomic.CompareAndSwapInt32(&m.state, old, new) {
-			runtime.Semrelease(&m.sema)
+			runtime_Semrelease(&m.sema)
 			return
 		}
 		old = m.state
diff --git a/libgo/go/sync/mutex_test.go b/libgo/go/sync/mutex_test.go
index a514b4a..bf78c6f 100644
--- a/libgo/go/sync/mutex_test.go
+++ b/libgo/go/sync/mutex_test.go
@@ -15,8 +15,8 @@ import (
 
 func HammerSemaphore(s *uint32, loops int, cdone chan bool) {
 	for i := 0; i < loops; i++ {
-		runtime.Semacquire(s)
-		runtime.Semrelease(s)
+		Runtime_Semacquire(s)
+		Runtime_Semrelease(s)
 	}
 	cdone <- true
 }
diff --git a/libgo/go/sync/runtime.go b/libgo/go/sync/runtime.go
new file mode 100644
index 0000000..e99599c
--- /dev/null
+++ b/libgo/go/sync/runtime.go
@@ -0,0 +1,18 @@
+// Copyright 2012 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 sync
+
+// defined in package runtime
+
+// 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 runtime_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 runtime_Semrelease(s *uint32)
diff --git a/libgo/go/sync/runtime_sema_test.go b/libgo/go/sync/runtime_sema_test.go
new file mode 100644
index 0000000..57a8dbe
--- /dev/null
+++ b/libgo/go/sync/runtime_sema_test.go
@@ -0,0 +1,101 @@
+// 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.
+
+package sync_test
+
+import (
+	"runtime"
+	. "sync"
+	"sync/atomic"
+	"testing"
+)
+
+func BenchmarkSemaUncontended(b *testing.B) {
+	type PaddedSem struct {
+		sem uint32
+		pad [32]uint32
+	}
+	const CallsPerSched = 1000
+	procs := runtime.GOMAXPROCS(-1)
+	N := int32(b.N / CallsPerSched)
+	c := make(chan bool, procs)
+	for p := 0; p < procs; p++ {
+		go func() {
+			sem := new(PaddedSem)
+			for atomic.AddInt32(&N, -1) >= 0 {
+				runtime.Gosched()
+				for g := 0; g < CallsPerSched; g++ {
+					Runtime_Semrelease(&sem.sem)
+					Runtime_Semacquire(&sem.sem)
+				}
+			}
+			c <- true
+		}()
+	}
+	for p := 0; p < procs; p++ {
+		<-c
+	}
+}
+
+func benchmarkSema(b *testing.B, block, work bool) {
+	const CallsPerSched = 1000
+	const LocalWork = 100
+	procs := runtime.GOMAXPROCS(-1)
+	N := int32(b.N / CallsPerSched)
+	c := make(chan bool, procs)
+	c2 := make(chan bool, procs/2)
+	sem := uint32(0)
+	if block {
+		for p := 0; p < procs/2; p++ {
+			go func() {
+				Runtime_Semacquire(&sem)
+				c2 <- true
+			}()
+		}
+	}
+	for p := 0; p < procs; p++ {
+		go func() {
+			foo := 0
+			for atomic.AddInt32(&N, -1) >= 0 {
+				runtime.Gosched()
+				for g := 0; g < CallsPerSched; g++ {
+					Runtime_Semrelease(&sem)
+					if work {
+						for i := 0; i < LocalWork; i++ {
+							foo *= 2
+							foo /= 2
+						}
+					}
+					Runtime_Semacquire(&sem)
+				}
+			}
+			c <- foo == 42
+			Runtime_Semrelease(&sem)
+		}()
+	}
+	if block {
+		for p := 0; p < procs/2; p++ {
+			<-c2
+		}
+	}
+	for p := 0; p < procs; p++ {
+		<-c
+	}
+}
+
+func BenchmarkSemaSyntNonblock(b *testing.B) {
+	benchmarkSema(b, false, false)
+}
+
+func BenchmarkSemaSyntBlock(b *testing.B) {
+	benchmarkSema(b, true, false)
+}
+
+func BenchmarkSemaWorkNonblock(b *testing.B) {
+	benchmarkSema(b, false, true)
+}
+
+func BenchmarkSemaWorkBlock(b *testing.B) {
+	benchmarkSema(b, true, true)
+}
diff --git a/libgo/go/sync/rwmutex.go b/libgo/go/sync/rwmutex.go
index cb1a477..782a9c3 100644
--- a/libgo/go/sync/rwmutex.go
+++ b/libgo/go/sync/rwmutex.go
@@ -4,10 +4,7 @@
 
 package sync
 
-import (
-	"runtime"
-	"sync/atomic"
-)
+import "sync/atomic"
 
 // An RWMutex is a reader/writer mutual exclusion lock.
 // The lock can be held by an arbitrary number of readers
@@ -29,7 +26,7 @@ const rwmutexMaxReaders = 1 << 30
 func (rw *RWMutex) RLock() {
 	if atomic.AddInt32(&rw.readerCount, 1) < 0 {
 		// A writer is pending, wait for it.
-		runtime.Semacquire(&rw.readerSem)
+		runtime_Semacquire(&rw.readerSem)
 	}
 }
 
@@ -42,7 +39,7 @@ func (rw *RWMutex) RUnlock() {
 		// A writer is pending.
 		if atomic.AddInt32(&rw.readerWait, -1) == 0 {
 			// The last reader unblocks the writer.
-			runtime.Semrelease(&rw.writerSem)
+			runtime_Semrelease(&rw.writerSem)
 		}
 	}
 }
@@ -60,7 +57,7 @@ func (rw *RWMutex) Lock() {
 	r := atomic.AddInt32(&rw.readerCount, -rwmutexMaxReaders) + rwmutexMaxReaders
 	// Wait for active readers.
 	if r != 0 && atomic.AddInt32(&rw.readerWait, r) != 0 {
-		runtime.Semacquire(&rw.writerSem)
+		runtime_Semacquire(&rw.writerSem)
 	}
 }
 
@@ -75,7 +72,7 @@ func (rw *RWMutex) Unlock() {
 	r := atomic.AddInt32(&rw.readerCount, rwmutexMaxReaders)
 	// Unblock blocked readers, if any.
 	for i := 0; i < int(r); i++ {
-		runtime.Semrelease(&rw.readerSem)
+		runtime_Semrelease(&rw.readerSem)
 	}
 	// Allow other writers to proceed.
 	rw.w.Unlock()
diff --git a/libgo/go/sync/waitgroup.go b/libgo/go/sync/waitgroup.go
index a4c9b7e..3e7d9d3 100644
--- a/libgo/go/sync/waitgroup.go
+++ b/libgo/go/sync/waitgroup.go
@@ -4,10 +4,7 @@
 
 package sync
 
-import (
-	"runtime"
-	"sync/atomic"
-)
+import "sync/atomic"
 
 // A WaitGroup waits for a collection of goroutines to finish.
 // The main goroutine calls Add to set the number of
@@ -60,7 +57,7 @@ func (wg *WaitGroup) Add(delta int) {
 	}
 	wg.m.Lock()
 	for i := int32(0); i < wg.waiters; i++ {
-		runtime.Semrelease(wg.sema)
+		runtime_Semrelease(wg.sema)
 	}
 	wg.waiters = 0
 	wg.sema = nil
@@ -93,5 +90,5 @@ func (wg *WaitGroup) Wait() {
 	}
 	s := wg.sema
 	wg.m.Unlock()
-	runtime.Semacquire(s)
+	runtime_Semacquire(s)
 }