Recursive property of the mutex operates with the term “owner“, which in case of a shared_mutex is not well-defined: several threads may have .lock_shared() called at the same time. Assuming “owner” to be a thread which calls .lock() (not .lock_shared()!), an implementation of the recursive shared mutex can be simply derived from shared_mutex: class shared_recursive_mutex: … Read more
It’s good practice to keep the mutex close to the data it is destined to protect. If a mutex ought to protect concurrent access to fields of a struct value, it’s very convenient to add the mutex as a field of that struct, so its purpose is obvious. If in your app there is only … Read more
I did it this way once, I hope it helps: bool createdNew; Mutex m = new Mutex(true, “myApp”, out createdNew); if (!createdNew) { // myApp is already running… MessageBox.Show(“myApp is already running!”, “Multiple Instances”); return; }
1) First code sample { static std::mutex io_mutex; std::lock_guard<std::mutex> lk(io_mutex); std::cout << e1.id << ” and ” << e2.id << ” are waiting for locks” << std::endl; } This is a standard lock guard, when the scope is exited, the lock lk is released { std::unique_lock<std::mutex> lk1(e1.m, std::defer_lock); std::unique_lock<std::mutex> lk2(e2.m, std::defer_lock); std::lock(lk1, lk2); std::cout << … Read more
The best place to find that information is from the POSIX standards pages. A NULL mutex attribute gives you an implementation defined default attribute. If you want to know what you can do with attributes, check out the following reference and follow the pthread_mutexattr_* links in the SEE ALSO section. Usually, the default is a … Read more
First, remember the goal of these ‘synchronizing objects’ : These objects were designed to provide an efficient and coherent use of ‘shared data’ between more than 1 thread among 1 process or from different processes. These objects can be ‘acquired’ or ‘released’. That is it!!! End of story!!! Now, if it helps to you, let … Read more
It is not supported because the std::mutex implementation uses GetCurrentThreadId(). That’s a winapi function that is not supposed to be use in managed code since it might be running on a custom CLR host that doesn’t use threads to implement threading. This is the good kind of problem to have, it shows that you are … Read more
As I understand this is covered in: 1.10 Multi-threaded executions and data races Para 5: The library defines a number of atomic operations (Clause 29) and operations on mutexes (Clause 30) that are specially identified as synchronization operations. These operations play a special role in making assignments in one thread visible to another. A synchronization … Read more
As Jon first suggested, you can try creating a mutex. Call CreateMutex. If you get a non-null handle back, then call GetLastError. It will tell you whether you were the one who created the mutex or whether the mutex was already open before (Error_Already_Exists). Note that it is not necessary to acquire ownership of the … Read more