More than one thread operating on a single Entity Framework context is not thread safe. A separate instance of context for each thread is thread-safe. As long as each thread of execution has its own instance of EF context you will be fine. In your example, you may call that code from any number of … Read more
Answer 1: static synchronized methods use the class object as the lock – ie in this case Singleton.class. Answer 2: The java language, among other things: loads classes when they are first accessed/used guarantees that before access to a class is allowed, all static initializers have completed These two facts mean that the inner static … Read more
So when an object is confined to a thread, no other thread can have access to it? No, it’s the other way around: if you ensure that no other thread has access to an object, then that object is said to be confined to a single thread. There’s no language- or JVM-level mechanism that confines … Read more
This is hardware-dependent. On hardware I am familiar with, C++ doesn’t have to do anything special, because from hardware perspective accessing different bytes even on a cached line is handled ‘transparently’. From the hardware, this situation is not really different from char a[2]; // or char a, b; In the cases above, we are talking … Read more
No. However, most of the time they will be. While it’s helpful to think of const as “thread-safe” and mutable as “(already) thread-safe”, const is still fundamentally tied to the notion of promising “I won’t change this value”. It always will be. I have a long-ish train of thought so bear with me. In my … Read more
First of all, forget about synchronized methods. A so-called synchronized method… synchronized AnyType foobar(…) { doSomething(); } Is nothing but a shortcut way of writing this: AnyType foobar(…) { synchronized(this) { doSomething(); } } There is nothing special about the method in either case. What is special is the synchronized block, and what a synchronized … Read more
Java Concurrency in Practice has some great information about how to write tests for concurrency issues. However they are not true unit tests. It is nearly impossible to write a true unit test for a concurrency issue. Basically it boils down to this. Create a bunch of test threads and start them. Each thread should … Read more
The write is atomic but an increment also requires a read. So the question is: Are you sure the read is safe, in other words, are you sure another thread doing the increment will not end up with the same value to be incremented? I have doubts. The 100% correct way of doing this would … Read more
Yes, reference updates are guaranteed to be atomic in the language spec. 5.5 Atomicity of variable references Reads and writes of the following data types are atomic: bool, char, byte, sbyte, short, ushort, uint, int, float, and reference types. In addition, reads and writes of enum types with an underlying type in the previous list … Read more
Problem I am afraid the test you have written is incorrect. The main requirement is to share the same StringBuilder instance between different threads. Whereas you are creating a StringBuilder object for each thread. The problem is that a new Threadsafe() initialises a new StringBuilder(): class Threadsafe { … StringBuilder sb = new StringBuilder(str); … … Read more