1 files changed, 195 insertions, 0 deletions
diff --git a/src/runtime/rwmutex_test.go b/src/runtime/rwmutex_test.go
new file mode 100644
index 0000000..bdeb9c4
--- /dev/null
+++ b/src/runtime/rwmutex_test.go
@@ -0,0 +1,195 @@
+// Copyright 2017 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 go test
+
+// This is a copy of sync/rwmutex_test.go rewritten to test the
+// runtime rwmutex.
+
+package runtime_test
+
+import (
+	"fmt"
+	. "runtime"
+	"runtime/debug"
+	"sync/atomic"
+	"testing"
+)
+
+func parallelReader(m *RWMutex, clocked chan bool, cunlock *atomic.Bool, cdone chan bool) {
+	m.RLock()
+	clocked <- true
+	for !cunlock.Load() {
+	}
+	m.RUnlock()
+	cdone <- true
+}
+
+func doTestParallelReaders(numReaders int) {
+	GOMAXPROCS(numReaders + 1)
+	var m RWMutex
+	m.Init()
+	clocked := make(chan bool, numReaders)
+	var cunlock atomic.Bool
+	cdone := make(chan bool)
+	for i := 0; i < numReaders; i++ {
+		go parallelReader(&m, clocked, &cunlock, cdone)
+	}
+	// Wait for all parallel RLock()s to succeed.
+	for i := 0; i < numReaders; i++ {
+		<-clocked
+	}
+	cunlock.Store(true)
+	// Wait for the goroutines to finish.
+	for i := 0; i < numReaders; i++ {
+		<-cdone
+	}
+}
+
+func TestParallelRWMutexReaders(t *testing.T) {
+	if GOARCH == "wasm" {
+		t.Skip("wasm has no threads yet")
+	}
+	defer GOMAXPROCS(GOMAXPROCS(-1))
+	// If runtime triggers a forced GC during this test then it will deadlock,
+	// since the goroutines can't be stopped/preempted.
+	// Disable GC for this test (see issue #10958).
+	defer debug.SetGCPercent(debug.SetGCPercent(-1))
+	// SetGCPercent waits until the mark phase is over, but the runtime
+	// also preempts at the start of the sweep phase, so make sure that's
+	// done too.
+	GC()
+
+	doTestParallelReaders(1)
+	doTestParallelReaders(3)
+	doTestParallelReaders(4)
+}
+
+func reader(rwm *RWMutex, num_iterations int, activity *int32, cdone chan bool) {
+	for i := 0; i < num_iterations; i++ {
+		rwm.RLock()
+		n := atomic.AddInt32(activity, 1)
+		if n < 1 || n >= 10000 {
+			panic(fmt.Sprintf("wlock(%d)\n", n))
+		}
+		for i := 0; i < 100; i++ {
+		}
+		atomic.AddInt32(activity, -1)
+		rwm.RUnlock()
+	}
+	cdone <- true
+}
+
+func writer(rwm *RWMutex, num_iterations int, activity *int32, cdone chan bool) {
+	for i := 0; i < num_iterations; i++ {
+		rwm.Lock()
+		n := atomic.AddInt32(activity, 10000)
+		if n != 10000 {
+			panic(fmt.Sprintf("wlock(%d)\n", n))
+		}
+		for i := 0; i < 100; i++ {
+		}
+		atomic.AddInt32(activity, -10000)
+		rwm.Unlock()
+	}
+	cdone <- true
+}
+
+func HammerRWMutex(gomaxprocs, numReaders, num_iterations int) {
+	GOMAXPROCS(gomaxprocs)
+	// Number of active readers + 10000 * number of active writers.
+	var activity int32
+	var rwm RWMutex
+	rwm.Init()
+	cdone := make(chan bool)
+	go writer(&rwm, num_iterations, &activity, cdone)
+	var i int
+	for i = 0; i < numReaders/2; i++ {
+		go reader(&rwm, num_iterations, &activity, cdone)
+	}
+	go writer(&rwm, num_iterations, &activity, cdone)
+	for ; i < numReaders; i++ {
+		go reader(&rwm, num_iterations, &activity, cdone)
+	}
+	// Wait for the 2 writers and all readers to finish.
+	for i := 0; i < 2+numReaders; i++ {
+		<-cdone
+	}
+}
+
+func TestRWMutex(t *testing.T) {
+	defer GOMAXPROCS(GOMAXPROCS(-1))
+	n := 1000
+	if testing.Short() {
+		n = 5
+	}
+	HammerRWMutex(1, 1, n)
+	HammerRWMutex(1, 3, n)
+	HammerRWMutex(1, 10, n)
+	HammerRWMutex(4, 1, n)
+	HammerRWMutex(4, 3, n)
+	HammerRWMutex(4, 10, n)
+	HammerRWMutex(10, 1, n)
+	HammerRWMutex(10, 3, n)
+	HammerRWMutex(10, 10, n)
+	HammerRWMutex(10, 5, n)
+}
+
+func BenchmarkRWMutexUncontended(b *testing.B) {
+	type PaddedRWMutex struct {
+		RWMutex
+		pad [32]uint32
+	}
+	b.RunParallel(func(pb *testing.PB) {
+		var rwm PaddedRWMutex
+		rwm.Init()
+		for pb.Next() {
+			rwm.RLock()
+			rwm.RLock()
+			rwm.RUnlock()
+			rwm.RUnlock()
+			rwm.Lock()
+			rwm.Unlock()
+		}
+	})
+}
+
+func benchmarkRWMutex(b *testing.B, localWork, writeRatio int) {
+	var rwm RWMutex
+	rwm.Init()
+	b.RunParallel(func(pb *testing.PB) {
+		foo := 0
+		for pb.Next() {
+			foo++
+			if foo%writeRatio == 0 {
+				rwm.Lock()
+				rwm.Unlock()
+			} else {
+				rwm.RLock()
+				for i := 0; i != localWork; i += 1 {
+					foo *= 2
+					foo /= 2
+				}
+				rwm.RUnlock()
+			}
+		}
+		_ = foo
+	})
+}
+
+func BenchmarkRWMutexWrite100(b *testing.B) {
+	benchmarkRWMutex(b, 0, 100)
+}
+
+func BenchmarkRWMutexWrite10(b *testing.B) {
+	benchmarkRWMutex(b, 0, 10)
+}
+
+func BenchmarkRWMutexWorkWrite100(b *testing.B) {
+	benchmarkRWMutex(b, 100, 100)
+}
+
+func BenchmarkRWMutexWorkWrite10(b *testing.B) {
+	benchmarkRWMutex(b, 100, 10)
+}