test/loops/CheckedLockLoops.java

/*
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/publicdomain/zero/1.0/
 */
/*
 * @test
 * @summary basic safety and liveness of ReentrantLocks, and other locks based on them
 */

import java.util.concurrent.Callable;
import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Semaphore;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

public final class CheckedLockLoops {
    static final ExecutorService pool = Executors.newCachedThreadPool();
    static final LoopHelpers.SimpleRandom rng = new LoopHelpers.SimpleRandom();
    static boolean print = false;
    static boolean doBuiltin = true;

    public static void main(String[] args) throws Exception {
        int maxThreads = 100;
        int iters = 2000000;
        if (args.length > 0)
            maxThreads = Integer.parseInt(args[0]);
        rng.setSeed(3122688L);
        warmup(iters);
        runTest(maxThreads, iters);
        pool.shutdown();
    }

    static void runTest(int maxThreads, int iters) throws Exception {
        print = true;
        for (int k = 1, i = 1; i <= maxThreads;) {
            System.out.println("Threads:" + i);
            oneTest(i, iters / i);
            if (i == k) {
                k = i << 1;
                i = i + (i >>> 1);
            }
            else
                i = k;
        }
    }

    static void warmup(int iters) throws Exception {
        print = false;
        System.out.println("Warmup...");
        oneTest(1, iters);
        oneTest(2, iters / 2);
    }

    static void oneTest(int nthreads, int iters) throws Exception {
        int fairIters = (nthreads <= 1) ? iters : iters/20;
        int v = rng.next();

        if (print)
            System.out.print("NoLock (1 thread)     ");
        new NoLockLoop().test(v, 1, iters * nthreads);
        Thread.sleep(10);

        if (print)
            System.out.print("ReentrantLock         ");
        new ReentrantLockLoop().test(v, nthreads, iters);
        Thread.sleep(10);

        if (print)
            System.out.print("FairReentrantLock     ");
        new FairReentrantLockLoop().test(v, nthreads, fairIters);
        Thread.sleep(10);

        if (doBuiltin) {
            if (print)
                System.out.print("builtin lock          ");
            new BuiltinLockLoop().test(v, nthreads, fairIters);
            Thread.sleep(10);
        }

        if (print)
            System.out.print("Mutex                 ");
        new MutexLoop().test(v, nthreads, iters);
        Thread.sleep(10);

        if (print)
            System.out.print("LongMutex             ");
        new LongMutexLoop().test(v, nthreads, iters);
        Thread.sleep(10);

        if (print)
            System.out.print("Semaphore             ");
        new SemaphoreLoop().test(v, nthreads, iters);
        Thread.sleep(10);

        if (print)
            System.out.print("FairSemaphore         ");
        new FairSemaphoreLoop().test(v, nthreads, fairIters);
        Thread.sleep(10);

        if (print)
            System.out.print("ReentrantWriteLock    ");
        new ReentrantWriteLockLoop().test(v, nthreads, iters);
        Thread.sleep(10);

        if (print)
            System.out.print("FairRWriteLock         ");
        new FairReentrantWriteLockLoop().test(v, nthreads, fairIters);
        Thread.sleep(10);

        if (print)
            System.out.print("ReentrantReadWriteLock");
        new ReentrantReadWriteLockLoop().test(v, nthreads, iters);
        Thread.sleep(10);

        if (print)
            System.out.print("FairRReadWriteLock     ");
        new FairReentrantReadWriteLockLoop().test(v, nthreads, fairIters);
        Thread.sleep(10);
    }

    abstract static class LockLoop implements Runnable {
        int value;
        int checkValue;
        int iters;
        volatile int result;
        volatile int failures;
        final LoopHelpers.BarrierTimer timer = new LoopHelpers.BarrierTimer();
        CyclicBarrier barrier;

        final int setValue(int v) {
            checkValue = v ^ 0x55555555;
            value = v;
            return v;
        }

        final int getValue() {
            int v = value;
            if (checkValue != ~(v ^ 0xAAAAAAAA))
                ++failures;
            return v;
        }

        final void test(int initialValue, int nthreads, int iters) throws Exception {
            setValue(initialValue);
            this.iters = iters;
            barrier = new CyclicBarrier(nthreads+1, timer);
            for (int i = 0; i < nthreads; ++i)
                pool.execute(this);
            barrier.await();
            barrier.await();
            long time = timer.getTime();
            if (print) {
                long tpi = time / (iters * nthreads);
                System.out.print("\t" + LoopHelpers.rightJustify(tpi) + " ns per update");
                System.out.println();
            }

            if (result == 0) // avoid overoptimization
                System.out.println("useless result: " + result);
            if (failures != 0)
                throw new Error("lock protection failure");
        }

        abstract int loop(int n);
        public final void run() {
            try {
                barrier.await();
                result += loop(iters);
                barrier.await();
            }
            catch (Exception ie) {
                return;
            }
        }

    }

    private static class NoLockLoop extends LockLoop {
        private volatile int readBarrier;
        final int loop(int n) {
            int sum = 0;
            int x = 0;
            while (n-- > 0) {
                int r1 = readBarrier;
                x = setValue(LoopHelpers.compute1(getValue()));
                int r2 = readBarrier;
                if (r1 == r2 && x == r1)
                    ++readBarrier;
                sum += LoopHelpers.compute2(x);
            }
            return sum;
        }
    }

    private static class BuiltinLockLoop extends LockLoop {
        final int loop(int n) {
            int sum = 0;
            int x = 0;
            while (n-- > 0) {
                synchronized (this) {
                    x = setValue(LoopHelpers.compute1(getValue()));
                }
                sum += LoopHelpers.compute2(x);
            }
            return sum;
        }
    }

    private static class ReentrantLockLoop extends LockLoop {
        private final ReentrantLock lock = new ReentrantLock();
        final int loop(int n) {
            final ReentrantLock lock = this.lock;
            int sum = 0;
            int x = 0;
            while (n-- > 0) {
                lock.lock();
                try {
                    x = setValue(LoopHelpers.compute1(getValue()));
                }
                finally {
                    lock.unlock();
                }
                sum += LoopHelpers.compute2(x);
            }
            return sum;
        }
    }

    private static class MutexLoop extends LockLoop {
        private final Mutex lock = new Mutex();
        final int loop(int n) {
            final Mutex lock = this.lock;
            int sum = 0;
            int x = 0;
            while (n-- > 0) {
                lock.lock();
                try {
                    x = setValue(LoopHelpers.compute1(getValue()));
                }
                finally {
                    lock.unlock();
                }
                sum += LoopHelpers.compute2(x);
            }
            return sum;
        }
    }

    private static class LongMutexLoop extends LockLoop {
        private final LongMutex lock = new LongMutex();
        final int loop(int n) {
            final LongMutex lock = this.lock;
            int sum = 0;
            int x = 0;
            while (n-- > 0) {
                lock.lock();
                try {
                    x = setValue(LoopHelpers.compute1(getValue()));
                }
                finally {
                    lock.unlock();
                }
                sum += LoopHelpers.compute2(x);
            }
            return sum;
        }
    }

    private static class FairReentrantLockLoop extends LockLoop {
        private final ReentrantLock lock = new ReentrantLock(true);
        final int loop(int n) {
            final ReentrantLock lock = this.lock;
            int sum = 0;
            int x = 0;
            while (n-- > 0) {
                lock.lock();
                try {
                    x = setValue(LoopHelpers.compute1(getValue()));
                }
                finally {
                    lock.unlock();
                }
                sum += LoopHelpers.compute2(x);
            }
            return sum;
        }
    }

    private static class ReentrantWriteLockLoop extends LockLoop {
        private final Lock lock = new ReentrantReadWriteLock().writeLock();
        final int loop(int n) {
            final Lock lock = this.lock;
            int sum = 0;
            int x = 0;
            while (n-- > 0) {
                lock.lock();
                try {
                    x = setValue(LoopHelpers.compute1(getValue()));
                }
                finally {
                    lock.unlock();
                }
                sum += LoopHelpers.compute2(x);
            }
            return sum;
        }
    }

    private static class FairReentrantWriteLockLoop extends LockLoop {
        final Lock lock = new ReentrantReadWriteLock(true).writeLock();
        final int loop(int n) {
            final Lock lock = this.lock;
            int sum = 0;
            int x = 0;
            while (n-- > 0) {
                lock.lock();
                try {
                    x = setValue(LoopHelpers.compute1(getValue()));
                }
                finally {
                    lock.unlock();
                }
                sum += LoopHelpers.compute2(x);
            }
            return sum;
        }
    }

    private static class SemaphoreLoop extends LockLoop {
        private final Semaphore sem = new Semaphore(1, false);
        final int loop(int n) {
            final Semaphore sem = this.sem;
            int sum = 0;
            int x = 0;
            while (n-- > 0) {
                sem.acquireUninterruptibly();
                try {
                    x = setValue(LoopHelpers.compute1(getValue()));
                }
                finally {
                    sem.release();
                }
                sum += LoopHelpers.compute2(x);
            }
            return sum;
        }
    }
    private static class FairSemaphoreLoop extends LockLoop {
        private final Semaphore sem = new Semaphore(1, true);
        final int loop(int n) {
            final Semaphore sem = this.sem;
            int sum = 0;
            int x = 0;
            while (n-- > 0) {
                sem.acquireUninterruptibly();
                try {
                    x = setValue(LoopHelpers.compute1(getValue()));
                }
                finally {
                    sem.release();
                }
                sum += LoopHelpers.compute2(x);
            }
            return sum;
        }
    }

    private static class ReentrantReadWriteLockLoop extends LockLoop {
        private final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
        final int loop(int n) {
            final Lock rlock = lock.readLock();
            final Lock wlock = lock.writeLock();
            int sum = 0;
            int x = 0;
            while (n-- > 0) {
                if ((n & 16) != 0) {
                    rlock.lock();
                    try {
                        x = LoopHelpers.compute1(getValue());
                        x = LoopHelpers.compute2(x);
                    }
                    finally {
                        rlock.unlock();
                    }
                }
                else {
                    wlock.lock();
                    try {
                        setValue(x);
                    }
                    finally {
                        wlock.unlock();
                    }
                    sum += LoopHelpers.compute2(x);
                }
            }
            return sum;
        }

    }

    private static class FairReentrantReadWriteLockLoop extends LockLoop {
        private final ReentrantReadWriteLock lock = new ReentrantReadWriteLock(true);
        final int loop(int n) {
            final Lock rlock = lock.readLock();
            final Lock wlock = lock.writeLock();
            int sum = 0;
            int x = 0;
            while (n-- > 0) {
                if ((n & 16) != 0) {
                    rlock.lock();
                    try {
                        x = LoopHelpers.compute1(getValue());
                        x = LoopHelpers.compute2(x);
                    }
                    finally {
                        rlock.unlock();
                    }
                }
                else {
                    wlock.lock();
                    try {
                        setValue(x);
                    }
                    finally {
                        wlock.unlock();
                    }
                    sum += LoopHelpers.compute2(x);
                }
            }
            return sum;
        }

    }
}
Revision:	1.12
Committed:	Sat Dec 31 18:54:28 2016 UTC (7 years, 4 months ago) by jsr166
Branch:	MAIN
Changes since 1.11:	+8 -3 lines
Log Message:	organize imports
#	User	Rev	Content
1	dl	1.1	/*
2	dl	1.2	* Written by Doug Lea with assistance from members of JCP JSR-166
3			* Expert Group and released to the public domain, as explained at
4	jsr166	1.8	* http://creativecommons.org/publicdomain/zero/1.0/
5	dl	1.2	*/
6			/*
7	dl	1.1	* @test
8			* @summary basic safety and liveness of ReentrantLocks, and other locks based on them
9			*/
10
11	jsr166	1.12	import java.util.concurrent.Callable;
12			import java.util.concurrent.CyclicBarrier;
13			import java.util.concurrent.ExecutorService;
14			import java.util.concurrent.Executors;
15			import java.util.concurrent.Semaphore;
16			import java.util.concurrent.locks.Lock;
17			import java.util.concurrent.locks.ReentrantLock;
18			import java.util.concurrent.locks.ReentrantReadWriteLock;
19	dl	1.1
20			public final class CheckedLockLoops {
21			static final ExecutorService pool = Executors.newCachedThreadPool();
22			static final LoopHelpers.SimpleRandom rng = new LoopHelpers.SimpleRandom();
23			static boolean print = false;
24			static boolean doBuiltin = true;
25
26			public static void main(String[] args) throws Exception {
27			int maxThreads = 100;
28			int iters = 2000000;
29	jsr166	1.4	if (args.length > 0)
30	dl	1.1	maxThreads = Integer.parseInt(args[0]);
31			rng.setSeed(3122688L);
32			warmup(iters);
33			runTest(maxThreads, iters);
34			pool.shutdown();
35			}
36
37			static void runTest(int maxThreads, int iters) throws Exception {
38			print = true;
39	jsr166	1.9	for (int k = 1, i = 1; i <= maxThreads;) {
40	dl	1.1	System.out.println("Threads:" + i);
41			oneTest(i, iters / i);
42			if (i == k) {
43			k = i << 1;
44			i = i + (i >>> 1);
45	jsr166	1.4	}
46			else
47	dl	1.1	i = k;
48			}
49	jsr166	1.4	}
50	dl	1.1
51			static void warmup(int iters) throws Exception {
52			print = false;
53			System.out.println("Warmup...");
54			oneTest(1, iters);
55			oneTest(2, iters / 2);
56			}
57
58			static void oneTest(int nthreads, int iters) throws Exception {
59	jsr166	1.5	int fairIters = (nthreads <= 1) ? iters : iters/20;
60	dl	1.1	int v = rng.next();
61
62			if (print)
63			System.out.print("NoLock (1 thread) ");
64			new NoLockLoop().test(v, 1, iters * nthreads);
65			Thread.sleep(10);
66	jsr166	1.4
67	dl	1.1	if (print)
68			System.out.print("ReentrantLock ");
69			new ReentrantLockLoop().test(v, nthreads, iters);
70			Thread.sleep(10);
71
72			if (print)
73			System.out.print("FairReentrantLock ");
74			new FairReentrantLockLoop().test(v, nthreads, fairIters);
75			Thread.sleep(10);
76
77			if (doBuiltin) {
78			if (print)
79			System.out.print("builtin lock ");
80			new BuiltinLockLoop().test(v, nthreads, fairIters);
81			Thread.sleep(10);
82			}
83
84			if (print)
85			System.out.print("Mutex ");
86			new MutexLoop().test(v, nthreads, iters);
87			Thread.sleep(10);
88
89			if (print)
90			System.out.print("LongMutex ");
91			new LongMutexLoop().test(v, nthreads, iters);
92			Thread.sleep(10);
93
94			if (print)
95			System.out.print("Semaphore ");
96			new SemaphoreLoop().test(v, nthreads, iters);
97			Thread.sleep(10);
98	jsr166	1.4
99	dl	1.1	if (print)
100			System.out.print("FairSemaphore ");
101			new FairSemaphoreLoop().test(v, nthreads, fairIters);
102			Thread.sleep(10);
103
104			if (print)
105			System.out.print("ReentrantWriteLock ");
106			new ReentrantWriteLockLoop().test(v, nthreads, iters);
107			Thread.sleep(10);
108
109			if (print)
110			System.out.print("FairRWriteLock ");
111			new FairReentrantWriteLockLoop().test(v, nthreads, fairIters);
112			Thread.sleep(10);
113	jsr166	1.4
114	dl	1.1	if (print)
115			System.out.print("ReentrantReadWriteLock");
116			new ReentrantReadWriteLockLoop().test(v, nthreads, iters);
117			Thread.sleep(10);
118	jsr166	1.4
119	dl	1.1	if (print)
120			System.out.print("FairRReadWriteLock ");
121			new FairReentrantReadWriteLockLoop().test(v, nthreads, fairIters);
122			Thread.sleep(10);
123			}
124
125	jsr166	1.7	abstract static class LockLoop implements Runnable {
126	dl	1.1	int value;
127			int checkValue;
128			int iters;
129			volatile int result;
130			volatile int failures;
131			final LoopHelpers.BarrierTimer timer = new LoopHelpers.BarrierTimer();
132			CyclicBarrier barrier;
133
134			final int setValue(int v) {
135			checkValue = v ^ 0x55555555;
136			value = v;
137			return v;
138			}
139
140			final int getValue() {
141			int v = value;
142	jsr166	1.4	if (checkValue != ~(v ^ 0xAAAAAAAA))
143	dl	1.1	++failures;
144			return v;
145			}
146
147			final void test(int initialValue, int nthreads, int iters) throws Exception {
148			setValue(initialValue);
149			this.iters = iters;
150			barrier = new CyclicBarrier(nthreads+1, timer);
151	jsr166	1.4	for (int i = 0; i < nthreads; ++i)
152	dl	1.1	pool.execute(this);
153			barrier.await();
154			barrier.await();
155			long time = timer.getTime();
156			if (print) {
157			long tpi = time / (iters * nthreads);
158			System.out.print("\t" + LoopHelpers.rightJustify(tpi) + " ns per update");
159			System.out.println();
160			}
161
162			if (result == 0) // avoid overoptimization
163			System.out.println("useless result: " + result);
164			if (failures != 0)
165			throw new Error("lock protection failure");
166			}
167
168			abstract int loop(int n);
169			public final void run() {
170			try {
171	jsr166	1.4	barrier.await();
172	dl	1.1	result += loop(iters);
173			barrier.await();
174			}
175	jsr166	1.4	catch (Exception ie) {
176			return;
177	dl	1.1	}
178			}
179
180			}
181
182			private static class NoLockLoop extends LockLoop {
183			private volatile int readBarrier;
184			final int loop(int n) {
185			int sum = 0;
186	jsr166	1.3	int x = 0;
187	dl	1.1	while (n-- > 0) {
188			int r1 = readBarrier;
189			x = setValue(LoopHelpers.compute1(getValue()));
190			int r2 = readBarrier;
191			if (r1 == r2 && x == r1)
192			++readBarrier;
193			sum += LoopHelpers.compute2(x);
194			}
195			return sum;
196			}
197			}
198
199			private static class BuiltinLockLoop extends LockLoop {
200			final int loop(int n) {
201			int sum = 0;
202	jsr166	1.3	int x = 0;
203	dl	1.1	while (n-- > 0) {
204	jsr166	1.6	synchronized (this) {
205	dl	1.1	x = setValue(LoopHelpers.compute1(getValue()));
206			}
207			sum += LoopHelpers.compute2(x);
208			}
209			return sum;
210			}
211			}
212
213			private static class ReentrantLockLoop extends LockLoop {
214	jsr166	1.7	private final ReentrantLock lock = new ReentrantLock();
215	dl	1.1	final int loop(int n) {
216			final ReentrantLock lock = this.lock;
217			int sum = 0;
218			int x = 0;
219			while (n-- > 0) {
220			lock.lock();
221			try {
222			x = setValue(LoopHelpers.compute1(getValue()));
223			}
224			finally {
225			lock.unlock();
226			}
227			sum += LoopHelpers.compute2(x);
228			}
229			return sum;
230			}
231			}
232
233			private static class MutexLoop extends LockLoop {
234	jsr166	1.7	private final Mutex lock = new Mutex();
235	dl	1.1	final int loop(int n) {
236			final Mutex lock = this.lock;
237			int sum = 0;
238			int x = 0;
239			while (n-- > 0) {
240			lock.lock();
241			try {
242			x = setValue(LoopHelpers.compute1(getValue()));
243			}
244			finally {
245			lock.unlock();
246			}
247			sum += LoopHelpers.compute2(x);
248			}
249			return sum;
250			}
251			}
252
253			private static class LongMutexLoop extends LockLoop {
254	jsr166	1.7	private final LongMutex lock = new LongMutex();
255	dl	1.1	final int loop(int n) {
256			final LongMutex lock = this.lock;
257			int sum = 0;
258			int x = 0;
259			while (n-- > 0) {
260			lock.lock();
261			try {
262			x = setValue(LoopHelpers.compute1(getValue()));
263			}
264			finally {
265			lock.unlock();
266			}
267			sum += LoopHelpers.compute2(x);
268			}
269			return sum;
270			}
271			}
272
273			private static class FairReentrantLockLoop extends LockLoop {
274	jsr166	1.7	private final ReentrantLock lock = new ReentrantLock(true);
275	dl	1.1	final int loop(int n) {
276			final ReentrantLock lock = this.lock;
277			int sum = 0;
278			int x = 0;
279			while (n-- > 0) {
280			lock.lock();
281			try {
282			x = setValue(LoopHelpers.compute1(getValue()));
283			}
284			finally {
285			lock.unlock();
286			}
287			sum += LoopHelpers.compute2(x);
288			}
289			return sum;
290			}
291			}
292
293			private static class ReentrantWriteLockLoop extends LockLoop {
294	jsr166	1.7	private final Lock lock = new ReentrantReadWriteLock().writeLock();
295	dl	1.1	final int loop(int n) {
296			final Lock lock = this.lock;
297			int sum = 0;
298			int x = 0;
299			while (n-- > 0) {
300			lock.lock();
301			try {
302			x = setValue(LoopHelpers.compute1(getValue()));
303			}
304			finally {
305			lock.unlock();
306			}
307			sum += LoopHelpers.compute2(x);
308			}
309			return sum;
310			}
311			}
312
313			private static class FairReentrantWriteLockLoop extends LockLoop {
314			final Lock lock = new ReentrantReadWriteLock(true).writeLock();
315			final int loop(int n) {
316			final Lock lock = this.lock;
317			int sum = 0;
318			int x = 0;
319			while (n-- > 0) {
320			lock.lock();
321			try {
322			x = setValue(LoopHelpers.compute1(getValue()));
323			}
324			finally {
325			lock.unlock();
326			}
327			sum += LoopHelpers.compute2(x);
328			}
329			return sum;
330			}
331			}
332
333			private static class SemaphoreLoop extends LockLoop {
334	jsr166	1.7	private final Semaphore sem = new Semaphore(1, false);
335	dl	1.1	final int loop(int n) {
336			final Semaphore sem = this.sem;
337			int sum = 0;
338			int x = 0;
339			while (n-- > 0) {
340			sem.acquireUninterruptibly();
341			try {
342			x = setValue(LoopHelpers.compute1(getValue()));
343			}
344			finally {
345			sem.release();
346			}
347			sum += LoopHelpers.compute2(x);
348			}
349			return sum;
350			}
351			}
352			private static class FairSemaphoreLoop extends LockLoop {
353	jsr166	1.7	private final Semaphore sem = new Semaphore(1, true);
354	dl	1.1	final int loop(int n) {
355			final Semaphore sem = this.sem;
356			int sum = 0;
357			int x = 0;
358			while (n-- > 0) {
359			sem.acquireUninterruptibly();
360			try {
361			x = setValue(LoopHelpers.compute1(getValue()));
362			}
363			finally {
364			sem.release();
365			}
366			sum += LoopHelpers.compute2(x);
367			}
368			return sum;
369			}
370			}
371
372			private static class ReentrantReadWriteLockLoop extends LockLoop {
373	jsr166	1.7	private final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
374	dl	1.1	final int loop(int n) {
375			final Lock rlock = lock.readLock();
376			final Lock wlock = lock.writeLock();
377			int sum = 0;
378			int x = 0;
379			while (n-- > 0) {
380			if ((n & 16) != 0) {
381			rlock.lock();
382			try {
383			x = LoopHelpers.compute1(getValue());
384			x = LoopHelpers.compute2(x);
385			}
386			finally {
387			rlock.unlock();
388			}
389			}
390			else {
391			wlock.lock();
392			try {
393			setValue(x);
394			}
395			finally {
396			wlock.unlock();
397			}
398			sum += LoopHelpers.compute2(x);
399			}
400			}
401			return sum;
402			}
403
404			}
405
406			private static class FairReentrantReadWriteLockLoop extends LockLoop {
407	jsr166	1.7	private final ReentrantReadWriteLock lock = new ReentrantReadWriteLock(true);
408	dl	1.1	final int loop(int n) {
409			final Lock rlock = lock.readLock();
410			final Lock wlock = lock.writeLock();
411			int sum = 0;
412			int x = 0;
413			while (n-- > 0) {
414			if ((n & 16) != 0) {
415			rlock.lock();
416			try {
417			x = LoopHelpers.compute1(getValue());
418			x = LoopHelpers.compute2(x);
419			}
420			finally {
421			rlock.unlock();
422			}
423			}
424			else {
425			wlock.lock();
426			try {
427			setValue(x);
428			}
429			finally {
430			wlock.unlock();
431			}
432			sum += LoopHelpers.compute2(x);
433			}
434			}
435			return sum;
436			}
437
438			}
439			}