subtree(users/wpcarro): docking briefcase at '24f5a642'

git-subtree-dir: users/wpcarro
git-subtree-mainline: 464bbcb15c
git-subtree-split: 24f5a642af
Change-Id: I6105b3762b79126b3488359c95978cadb3efa789

users/wpcarro/go/mutex.go

@@ -0,0 +1,53 @@
+package main
+
+import (
+	"fmt"
+	"math/rand"
+	"sync"
+	"sync/atomic"
+	"time"
+)
+
+func main() {
+	state := make(map[int]int)
+	mux := &sync.Mutex{}
+
+	var readOps uint64
+	var writeOps uint64
+
+	// Read from state
+	for i := 0; i < 1000; i += 1 {
+		for j := 0; j < 100; j += 1 {
+			go func() {
+				key := rand.Intn(5)
+				mux.Lock()
+				fmt.Printf("state[%d] = %d\n", key, state[key])
+				mux.Unlock()
+				atomic.AddUint64(&readOps, 1)
+				time.Sleep(time.Millisecond)
+			}()
+		}
+	}
+
+	// Write to state
+	for i := 0; i < 10; i += 1 {
+		for j := 0; j < 100; j += 1 {
+			go func() {
+				key := rand.Intn(5)
+				mux.Lock()
+				state[key] += 1
+				mux.Unlock()
+				fmt.Printf("Wrote to state[%d].\n", key)
+				atomic.AddUint64(&writeOps, 1)
+				time.Sleep(time.Millisecond)
+			}()
+		}
+	}
+
+	time.Sleep(time.Millisecond)
+
+	mux.Lock()
+	fmt.Printf("State: %v\n", state)
+	mux.Unlock()
+	fmt.Printf("Reads: %d\tWrites: %d\n", atomic.LoadUint64(&readOps), atomic.LoadUint64(&writeOps))
+}