I continue my journey with concurrency patterns in today's post. The Thread-Safe Interface fits very well when the critical sections are just objects.

Dealing with Mutation: Thread-Safe Interface

by Rainer Grimm

From the article:

The naive idea to protect all member functions of a class with a lock causes, in the best case, a performance issue and, in the worst case, a deadlock.

A Deadlock

The small code snippet has a deadlock.

struct Critical{
    void memberFunction1(){
        lock(mut);
        memberFunction2();
    ...
}

void memberFunction2(){
        lock(mut);
        ...
    }

    mutex mut;
};

Critical crit;
crit.memberFunction1();

Calling crit.memberFunction1 causes the mutex mut to be locked twice. For simplicity reasons, the lock is a scoped lock. Here are the two issues: