Yes, it will. Regardless of nesting, if an atomic block is exited by an exception it will roll back: If the block of code is successfully completed, the changes are committed to the database. If there is an exception, the changes are rolled back. Note also that an exception in an outer block will cause … Read more
Since no answer to the actual question has been given, here’s my personal opinion based on the other answers (thanks, upvoted) and Java convention: incrementAndGet() is better, because method names should start with the verb describing the action, and intended action here is to increment only. Starting with verb is the common Java convention, also … Read more
The standard does not specify a specialization of std::atomic<std::string>, so the generic template <typename T> std::atomic<T> applies. 29.5 [atomics.types.generic] p1 states: There is a generic class template atomic. The type of the template argument T shall be trivially copyable (3.9). There is no statement that the implementation must diagnose violations of this requirement. So either … Read more
The main difference between AtomicBoolean and volatile from a practical point of view is that the compare-and-set operation isn’t atomic with volatile variables. volatile boolean b; void foo() { if( b ) { //Here another thread might have already changed the value of b to false b = false; } } But seeing as all … Read more
An ‘atomic write’ is one where you are guaranteed to have either a correct, complete write to the file or an error. There’s no chance that, say, half of the write will work and then something bad happens (lost power, drive crash, etc) and the rest of the write fails. It’s all or nothing. This … Read more
For something more complete/detailed: Reads and writes to 32-bit value types are atomic: This includes the following intrinsic value (struct) types: bool, char, byte, sbyte, short, ushort, int, uint, float. The following types (amongst others) are not guaranteed to be atomic: decimal, double, long, ulong. e.g. int x; x = 10; // atomic decimal d; … Read more
Atomicity Documentation To summarize, @transaction.atomic will execute a transaction on the database if your view produces a response without errors. Because you’re catching the exception yourself, it appears to Django that your view executed just fine. If you catch the exception, you need to handle it yourself: Controlling Transactions If you need to produce a … Read more
No, fundamental data types (e.g., int, double) are not atomic, see std::atomic. Instead you can use std::atomic<int> or std::atomic<double>. Note: std::atomic was introduced with C++11 and my understanding is that prior to C++11, the C++ standard didn’t recognize the existence of multithreading at all. As pointed out by @Josh, std::atomic_flag is an atomic boolean type. … Read more
Here is an article over at software.intel.com on that sheds little light on user level locks: User level locks involve utilizing the atomic instructions of processor to atomically update a memory space. The atomic instructions involve utilizing a lock prefix on the instruction and having the destination operand assigned to a memory address. The following … Read more
std::atomic bool type not guranteed to be lock-free? Correct. std::atomic may be implemented using locks. then it’s not atomic or what? std::atomic is atomic whether it has been implemented using locks, or without. std::atomic_flag is guaranteed to be implemented without using locks. So what’s the difference b/w two The primary difference besides the lock-free guarantee … Read more