test-and-set modifies the contents of a memory location and returns its old value as a single atomic operation. compare-and-swap atomically compares the contents of a memory location to a given value and, only if they are the same, modifies the contents of that memory location to a given new value. The difference marked in bold.
If you are using Spring’s Java-configuration, your config class needs to implements AsyncConfigurer: @Configuration @EnableAsync public class AppConfig implements AsyncConfigurer { […] @Override public Executor getAsyncExecutor() { ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor(); executor.setCorePoolSize(2); executor.setMaxPoolSize(5); executor.setQueueCapacity(50); executor.setThreadNamePrefix(“MyExecutor-“); executor.initialize(); return executor; } } See @EnableAsync documentation for more details : http://docs.spring.io/spring/docs/3.1.x/javadoc-api/org/springframework/scheduling/annotation/EnableAsync.html
i = 1 always happens-before v = 2 True. By JLS section 17.4.5, If x and y are actions of the same thread and x comes before y in program order, then hb(x, y). v = 2 happens-before vDst = v in JMM only if it’s actually happens before in time i = 1 happens-before … Read more
Whenever a thread calls the Thread.yield() method, it gives a hint to the thread scheduler that it is ready to pause its execution. The thread scheduler is free to ignore this hint. If any thread executes the yield method, the thread scheduler checks if there is any runnable (waiting to be executed) thread with same … Read more
I guess that the optimizer is fooled by the lack of ‘volatile’ keyword on the isComplete variable. Of course, you cannot add it, because it’s a local variable. And of course, since it is a local variable, it should not be needed at all, because locals are kept on stack and they are naturally always … Read more
The volatile prevents memory writes from being re-ordered, making it impossible for other threads to read uninitialized fields of your singleton through the singleton’s pointer. Consider this situation: thread A discovers that uniqueInstance == null, locks, confirms that it’s still null, and calls singleton’s constructor. The constructor makes a write into member XYZ inside Singleton, … Read more
The answer lies in java.lang.Object.wait(long) whose documentation says: […] This method causes the current thread (call it T) to place itself in the wait set for this object and then to relinquish any and all synchronization claims on this object. […]
First, let me introduce some terminology. A critical section (CS) is a sequence of instructions that can be executed by at most one process at the same time. When using critical sections, the code can be broken down into the following sections: // Some arbitrary code (such as initialization). EnterCriticalSection(cs); // The code that constitutes … Read more