Question

Do I need a mutex if I have only one reader and one writer? The reader takes the next command (food.front()) from the queue and executes a task based on the command. After the command is executed, it pops off the command. The writer to the queue pushes commands onto the queue (food.push()).

Do I need a mutex? My reader (consumer) only executes if food.size() > 0. I am using a reader thread and send thread.

Answer 1

A mutex is used in multi-threaded environments. I don’t see mention of threads in your question, so I don’t see a need for a mutex.

However, if we assume by reader and writer you mean you have two threads, you need to protect mutual data with a mutex (or other multi-threaded protection scheme.)

What happens when the queue has items, and the reader thread pops something off while the writer thread puts something on? Disaster! With a mutex, you’ll be sure only one thread is operating on the queue at a time.

Another method is a lock-free thread-safe queue. It would use atomic operations to ensure the data isn’t manipulated incorrectly.