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Awakening all threads solves guarantess guarantees the liveness property because each thread will execute its condition predicate test, and exactly one will succeed and continue execution.
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Another compilant solution is to use a unique condition variable for each thread (all associated with a single mutex). In this case, the signal operation (cnd_signal()) wakes up only the thread that is waiting on it. This solution is more efficient than using cnd_broadcast() because only the desired thread is awakened.
Note : that the condition predicate of the signaled thread must be true; otherwise, a deadlock will occur.
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