JavaScriptCore-7601.1.46.3.tar.gz

[apple/javascriptcore.git] / API / tests / CompareAndSwapTest.cpp

diff --git a/API/tests/CompareAndSwapTest.cpp b/API/tests/CompareAndSwapTest.cpp
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+/*
+ * Copyright (C) 2015 Apple Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
+ * THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "config.h"
+#include "CompareAndSwapTest.h"
+
+#include <stdio.h>
+#include <wtf/Atomics.h>
+#include <wtf/Threading.h>
+
+class Bitmap {
+public:
+    Bitmap() { clearAll(); }
+
+    inline void clearAll();
+    inline bool concurrentTestAndSet(size_t n);
+    inline size_t numBits() const { return words * wordSize; }
+
+private:
+    static const size_t Size = 4096*10;
+
+    static const unsigned wordSize = sizeof(uint8_t) * 8;
+    static const unsigned words = (Size + wordSize - 1) / wordSize;
+    static const uint8_t one = 1;
+
+    uint8_t bits[words];
+};
+
+inline void Bitmap::clearAll()
+{
+    memset(&bits, 0, sizeof(bits));
+}
+
+inline bool Bitmap::concurrentTestAndSet(size_t n)
+{
+    uint8_t mask = one << (n % wordSize);
+    size_t index = n / wordSize;
+    uint8_t* wordPtr = &bits[index];
+    uint8_t oldValue;
+    do {
+        oldValue = *wordPtr;
+        if (oldValue & mask)
+            return true;
+    } while (!WTF::weakCompareAndSwap(wordPtr, oldValue, oldValue | mask));
+    return false;
+}
+
+struct Data {
+    Bitmap* bitmap;
+    int id;
+    int numThreads;
+};
+
+static void setBitThreadFunc(void* p)
+{
+    Data* data = reinterpret_cast<Data*>(p);
+    Bitmap* bitmap = data->bitmap;
+    size_t numBits = bitmap->numBits();
+
+    // The computed start index here is heuristic that seems to maximize (anecdotally)
+    // the chance for the CAS issue to manifest.
+    size_t start = (numBits * (data->numThreads - data->id)) / data->numThreads;
+
+    printf("   started Thread %d\n", data->id);
+    for (size_t i = start; i < numBits; i++)
+        while (!bitmap->concurrentTestAndSet(i)) { }
+    for (size_t i = 0; i < start; i++)
+        while (!bitmap->concurrentTestAndSet(i)) { }
+
+    printf("   finished Thread %d\n", data->id);
+}
+
+void testCompareAndSwap()
+{
+    Bitmap bitmap;
+    const int numThreads = 5;
+    ThreadIdentifier threadIDs[numThreads];
+    Data data[numThreads];
+
+    WTF::initializeThreading();
+    
+    printf("Starting %d threads for CompareAndSwap test.  Test should complete without hanging.\n", numThreads);
+    for (int i = 0; i < numThreads; i++) {
+        data[i].bitmap = &bitmap;
+        data[i].id = i;
+        data[i].numThreads = numThreads;
+        std::function<void()> threadFunc = std::bind(setBitThreadFunc, &data[i]);
+        threadIDs[i] = createThread("setBitThreadFunc", threadFunc);
+    }
+
+    printf("Waiting for %d threads to join\n", numThreads);
+    for (int i = 0; i < numThreads; i++)
+        waitForThreadCompletion(threadIDs[i]);
+
+    printf("PASS: CompareAndSwap test completed without a hang\n");
+}