In C , condition_variables are used to efficiently handle multi-threaded synchronization scenarios. When using condition_variables, it's crucial to understand the role of locks in conjunction with their methods.
While it's not mandatory to hold a lock before calling condition_variable::notify_one(), it's generally considered good practice not to. However, there are a few reasons why you might choose to do so:
In the example provided, the first call to condition_variable::notify_one() is made without holding the lock, while subsequent calls acquire the lock first. This approach is valid and serves to prevent deadlocks as described earlier.
First notify_one() without Lock:
Subsequent notify_one() with Lock:
While holding the lock before notify_one() can prevent deadlocks, it may also lead to performance degradation.
Holding the lock forces the scheduling of the waits() thread, which may already be ready to run. This can cause unnecessary context switches and affect performance.
Whether or not to hold a lock before calling condition_variable::notify_one() depends on the specific scenario and performance requirements. If deadlock avoidance is a concern, holding the lock is recommended. If performance is a priority, notifying without holding the lock may be preferable. However, it's essential to consider the overall thread safety implications and design a robust synchronization strategy accordingly.
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