Learning about condition variables, read-write locks, and ranges in C++

Let’s now start our discussion of synchronization primitives, a fundamental one of which is the condition variable. Its purpose is to allow multiple threads to remain blocked until an event occurs (i.e., a condition is satisfied). The implementation of condition variables requires an additional Boolean variable to indicate whether the condition is met or not, a mutex to serialize the access to the Boolean variable, and the condition variable itself.

POSIX provides an interface for multiple use cases. Do you remember the producer-consumer example in Chapter 7, Using Shared Memory? So, pthread_cond_timedwait() is used to block a thread for a given period of time. Or simply wait for a condition through pthread_cond_wait () and signal with pthread_cond_signal() to one thread, or pthread_cond_broadcast() to all threads. Typically, the condition is checked periodically in the scope of a mutex lock:

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