dcapwell commented on code in PR #3408: URL: https://github.com/apache/cassandra/pull/3408#discussion_r1674720471
########## test/simulator/main/org/apache/cassandra/simulator/systems/InterceptingSemaphore.java: ########## @@ -0,0 +1,187 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance + * with the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +package org.apache.cassandra.simulator.systems; + +import java.util.Queue; +import java.util.concurrent.ConcurrentLinkedQueue; +import java.util.concurrent.TimeUnit; +import java.util.concurrent.atomic.AtomicInteger; + +import org.apache.cassandra.utils.Clock; +import org.apache.cassandra.utils.concurrent.Semaphore; +import org.apache.cassandra.utils.concurrent.UncheckedInterruptedException; + +import static org.apache.cassandra.simulator.systems.InterceptorOfGlobalMethods.Global.ifIntercepted; + +public class InterceptingSemaphore extends Semaphore.Standard +{ + final Queue<SemaphoreSignal> interceptible = new ConcurrentLinkedQueue<>(); + final AtomicInteger permits; + final boolean fair; + + private static class SemaphoreSignal extends InterceptingAwaitable.InterceptingSignal<Void> + { + private final int permits; + + private SemaphoreSignal(int permits) + { + this.permits = permits; + } + } + + public InterceptingSemaphore(int permits, boolean fair) + { + super(permits); + this.permits = new AtomicInteger(permits); + this.fair = fair; + } + + @Override + public int permits() + { + if (ifIntercepted() == null) + return super.permits(); + + return permits.get(); + } + + @Override + public int drain() + { + if (ifIntercepted() == null) + return super.drain(); + + for (int i = 0; i < 10; i++) + { + int current = permits.get(); + if (permits.compareAndSet(current, 0)) + return current; + } + + throw new IllegalStateException("Too much contention"); + } + + @Override + public void release(int release) + { + if (ifIntercepted() == null) + { + super.release(release); + return; + } + + int remaining = permits.addAndGet(release); + while (!interceptible.isEmpty() && remaining > 0) + { + SemaphoreSignal signal = interceptible.peek(); + if (signal.permits >= remaining) + interceptible.poll().signal(); + else if (fair) + // Do not break enqueue order if using fair scheduler + break; + } + } + + @Override + public boolean tryAcquire(int acquire) + { + if (ifIntercepted() == null) + return super.tryAcquire(acquire); + + for (int i = 0; i < 10; i++) + { + int current = permits.get(); + if (current >= acquire) + { + if (permits.compareAndSet(current, current - acquire)) + return true; + } + else + { + return false; + } + } + throw new IllegalStateException("Too much contention"); + } + + @Override + public boolean tryAcquire(int acquire, long time, TimeUnit unit) throws InterruptedException + { + if (ifIntercepted() == null) + return super.tryAcquire(acquire, time, unit); + + return tryAcquireUntil(acquire, Clock.Global.nanoTime() + unit.toNanos(time)); Review Comment: `Clock.Global.nanoTime()` is this right in the context of Simulator? This feels wrong to me... ########## test/simulator/test/org/apache/cassandra/simulator/test/TrivialSimulationTest.java: ########## @@ -85,9 +97,97 @@ public void componentTest() } @Test - public void identityHashMapTest() + public void semaphoreTest() { - simulate(arr(() -> new IdentityHashMap<>().put(1, 1)), - () -> {}); + long seed = System.currentTimeMillis(); + semaphoreTestInternal(seed); + State.record = false; + // Verify that subsequent interleavings will be the same + semaphoreTestInternal(seed); + } + + protected void semaphoreTestInternal(long seed) + { + simulate(arr(() -> { + ExecutorPlus executor = ExecutorFactory.Global.executorFactory().pooled("semaphore-test-", 10); + Semaphore semaphore = Semaphore.newSemaphore(5); + CountDownLatch latch = CountDownLatch.newCountDownLatch(5); + + for (int i = 0; i < 5; i++) + { + int thread = i; + executor.submit(() -> { + for (int j = 0; j < 100; j++) + { + int permits = semaphore.permits(); + Assert.assertTrue(permits + " should be non negative", permits >= 0); + + try + { + semaphore.acquire(1); + State.tick(thread, j); + semaphore.release(1); + } + catch (Throwable e) + { + throw new RuntimeException(e); + } + } + latch.decrement(); + }); + } + + latch.awaitUninterruptibly(); + int permits = semaphore.permits(); + Assert.assertEquals(5, permits); + }), + () -> {}, + seed); + } + + @Shared + public static class State + { + static final List<Tick> ticks = new ArrayList<>(); + static boolean record = true; + static int i = 0; + + public static void tick(int thread, int iteration) Review Comment: is this thread safe? I don't think so ########## test/simulator/main/org/apache/cassandra/simulator/systems/InterceptingSemaphore.java: ########## @@ -0,0 +1,187 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance + * with the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +package org.apache.cassandra.simulator.systems; + +import java.util.Queue; +import java.util.concurrent.ConcurrentLinkedQueue; +import java.util.concurrent.TimeUnit; +import java.util.concurrent.atomic.AtomicInteger; + +import org.apache.cassandra.utils.Clock; +import org.apache.cassandra.utils.concurrent.Semaphore; +import org.apache.cassandra.utils.concurrent.UncheckedInterruptedException; + +import static org.apache.cassandra.simulator.systems.InterceptorOfGlobalMethods.Global.ifIntercepted; + +public class InterceptingSemaphore extends Semaphore.Standard +{ + final Queue<SemaphoreSignal> interceptible = new ConcurrentLinkedQueue<>(); + final AtomicInteger permits; + final boolean fair; + + private static class SemaphoreSignal extends InterceptingAwaitable.InterceptingSignal<Void> + { + private final int permits; + + private SemaphoreSignal(int permits) + { + this.permits = permits; + } + } + + public InterceptingSemaphore(int permits, boolean fair) + { + super(permits); + this.permits = new AtomicInteger(permits); + this.fair = fair; + } + + @Override + public int permits() + { + if (ifIntercepted() == null) + return super.permits(); + + return permits.get(); + } + + @Override + public int drain() + { + if (ifIntercepted() == null) + return super.drain(); + + for (int i = 0; i < 10; i++) + { + int current = permits.get(); + if (permits.compareAndSet(current, 0)) + return current; + } + + throw new IllegalStateException("Too much contention"); + } + + @Override + public void release(int release) + { + if (ifIntercepted() == null) + { + super.release(release); + return; + } + + int remaining = permits.addAndGet(release); + while (!interceptible.isEmpty() && remaining > 0) + { + SemaphoreSignal signal = interceptible.peek(); + if (signal.permits >= remaining) + interceptible.poll().signal(); + else if (fair) + // Do not break enqueue order if using fair scheduler + break; + } + } + + @Override + public boolean tryAcquire(int acquire) + { + if (ifIntercepted() == null) + return super.tryAcquire(acquire); + + for (int i = 0; i < 10; i++) + { + int current = permits.get(); + if (current >= acquire) + { + if (permits.compareAndSet(current, current - acquire)) + return true; + } + else + { + return false; + } + } + throw new IllegalStateException("Too much contention"); + } + + @Override + public boolean tryAcquire(int acquire, long time, TimeUnit unit) throws InterruptedException + { + if (ifIntercepted() == null) + return super.tryAcquire(acquire, time, unit); + + return tryAcquireUntil(acquire, Clock.Global.nanoTime() + unit.toNanos(time)); + } + + @Override + public boolean tryAcquireUntil(int acquire, long deadline) throws InterruptedException + { + if (ifIntercepted() == null) + return super.tryAcquireUntil(acquire, deadline); + + do + { + int current = permits.get(); + if (current >= acquire) + { + if (permits.compareAndSet(current, current - acquire)) + return true; + } + SemaphoreSignal signal = new SemaphoreSignal(acquire); + interceptible.add(signal); + signal.awaitUntil(deadline); + } + while (Clock.Global.nanoTime() < deadline); Review Comment: if we waited until the deadline, then check again and not able to get the lock... shouldn't we stop right away? If we loop again are we not doing it wrong? ########## test/simulator/main/org/apache/cassandra/simulator/systems/InterceptingSemaphore.java: ########## @@ -0,0 +1,187 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance + * with the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +package org.apache.cassandra.simulator.systems; + +import java.util.Queue; +import java.util.concurrent.ConcurrentLinkedQueue; +import java.util.concurrent.TimeUnit; +import java.util.concurrent.atomic.AtomicInteger; + +import org.apache.cassandra.utils.Clock; +import org.apache.cassandra.utils.concurrent.Semaphore; +import org.apache.cassandra.utils.concurrent.UncheckedInterruptedException; + +import static org.apache.cassandra.simulator.systems.InterceptorOfGlobalMethods.Global.ifIntercepted; + +public class InterceptingSemaphore extends Semaphore.Standard +{ + final Queue<SemaphoreSignal> interceptible = new ConcurrentLinkedQueue<>(); + final AtomicInteger permits; + final boolean fair; + + private static class SemaphoreSignal extends InterceptingAwaitable.InterceptingSignal<Void> + { + private final int permits; + + private SemaphoreSignal(int permits) + { + this.permits = permits; + } + } + + public InterceptingSemaphore(int permits, boolean fair) + { + super(permits); + this.permits = new AtomicInteger(permits); + this.fair = fair; + } + + @Override + public int permits() + { + if (ifIntercepted() == null) + return super.permits(); + + return permits.get(); + } + + @Override + public int drain() + { + if (ifIntercepted() == null) + return super.drain(); + + for (int i = 0; i < 10; i++) + { + int current = permits.get(); + if (permits.compareAndSet(current, 0)) + return current; + } + + throw new IllegalStateException("Too much contention"); + } + + @Override + public void release(int release) + { + if (ifIntercepted() == null) + { + super.release(release); + return; + } + + int remaining = permits.addAndGet(release); + while (!interceptible.isEmpty() && remaining > 0) + { + SemaphoreSignal signal = interceptible.peek(); + if (signal.permits >= remaining) + interceptible.poll().signal(); + else if (fair) + // Do not break enqueue order if using fair scheduler + break; + } + } + + @Override + public boolean tryAcquire(int acquire) + { + if (ifIntercepted() == null) + return super.tryAcquire(acquire); + + for (int i = 0; i < 10; i++) + { + int current = permits.get(); + if (current >= acquire) + { + if (permits.compareAndSet(current, current - acquire)) + return true; + } + else + { + return false; + } + } + throw new IllegalStateException("Too much contention"); + } + + @Override + public boolean tryAcquire(int acquire, long time, TimeUnit unit) throws InterruptedException + { + if (ifIntercepted() == null) + return super.tryAcquire(acquire, time, unit); + + return tryAcquireUntil(acquire, Clock.Global.nanoTime() + unit.toNanos(time)); + } + + @Override + public boolean tryAcquireUntil(int acquire, long deadline) throws InterruptedException + { + if (ifIntercepted() == null) + return super.tryAcquireUntil(acquire, deadline); + + do + { + int current = permits.get(); + if (current >= acquire) + { + if (permits.compareAndSet(current, current - acquire)) + return true; + } + SemaphoreSignal signal = new SemaphoreSignal(acquire); + interceptible.add(signal); + signal.awaitUntil(deadline); + } + while (Clock.Global.nanoTime() < deadline); Review Comment: `Clock.Global.nanoTime()` feels wrong as time is owned by Simulator, so the logical time could be multiple hours but the physical time is just a few ms, which would lead to this doing the wrong behavior (and being non-deterministic)? -- This is an automated message from the Apache Git Service. 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