Hip Hop Ejay 3 (street Style Ejay) [full] [pl]. While the purpose of threads is to allow code to run in parallel, there are times where threads must stop and wait for other threads. For example, if two threads try to write to the same variable simultaneously, the result is undefined. The principle of forcing threads to wait for one another is called mutual exclusion. It is a common technique for protecting shared resources such as data. Qt provides low-level primitives as well as high-level mechanisms for synchronizing threads. Low-Level Synchronization Primitives is the basic class for enforcing mutual exclusion.

A thread locks a mutex in order to gain access to a shared resource. If a second thread tries to lock the mutex while it is already locked, the second thread will be put to sleep until the first thread completes its task and unlocks the mutex. Is similar to, except that it distinguishes between 'read' and 'write' access. When a piece of data is not being written to, it is safe for multiple threads to read from it simultaneously. A forces multiple readers to take turns to read shared data, but a allows simultaneous reading, thus improving parallelism. Is a generalization of that protects a certain number of identical resources. In contrast, a protects exactly one resource.