Condition Variable and cond_signal() Operation in C Programming

What happens when a thread executes cond_signal() on a condition variable? When a thread executes cond_signal() on a condition variable (CV), the value of CV is increased by 1 in an atomic fashion. It does not decrease the value or suspend the thread. If no threads are waiting on CV, the signal operation has no effect.

When a thread executes cond_signal() on a condition variable (CV), the value of CV is increased by 1 in an atomic fashion. This means that the signal operation is performed as a single, indivisible unit. It does not decrease the value of CV or suspend the thread.

However, if there are no waiting threads on CV, the signal operation has no effect. When thread T executes cond_signal() on a condition variable CV, it basically signifies that it is announcing a change in the state of some resource that other threads might be waiting for.

1. Executing cond_signal() does not alter the CV's value in an atomic way; it's not a counter, but a synchronization construct.

2. Thread T is not suspended. The cond_signal() function informs a thread waiting on the condition variable that the condition it was waiting for has been met, allowing that thread to proceed, but does not suspend the signalling thread.

3. If no threads are waiting on the CV, executing cond_signal() has no particular effect.

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