Keywords: perfbook_html

## B.3.5 Example Usage

A spinlock named mutex may be used to protect a variable counter as follows:

    spin_lock(&mutex);
    counter++;
    spin_unlock(&mutex);

Quick Quiz B.2: What problems could occur if the variable `counter` were incremented without the protection of `mutex`? End Quick Quiz

However, the spin_lock() and spin_unlock() primitives do have performance consequences, as will be seen in Section .