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Explore the concept of spurious wakeups in condition variables and understand the idiomatic Ruby pattern for waiting with mutex locks. Learn why using a while loop to check predicates is crucial for thread safety and how to synchronize signal calls using mutexes. This lesson also includes a practical example of a ping-pong concurrency problem with multiple threads, demonstrating how to maintain safe mutual exclusion with condition variables and broadcasting in Ruby.
We'll cover the following...
Spurious Wakeups
Condition variables suffer from spurious wakeups - that is, wakeup of threads waiting on the condition variable without being signaled. This is specifically allowed by the POSIX standard because it allows more efficient implementations of condition variables under some circumstances. Even though the official documentation doesn't mention this peculiarity, it is a common pattern across all programming languages including Python, Java, etc.
Idiomatic Usage
The idiomatic usage of condition variables when ...