javac++lock-freecompare-and-swaplockless

Advantages and disadvantages of CAS programming

Can anyone give me a summary of the advantages and disadvantages of Compare And Swap programming ? (e.g. multi-core CPU performance)

Here's and example in Java:

/**
 * Atomically increments by one the current value.
 *
 * @return the updated value
 */
public final int incrementAndGet() {
    for (;;) {
        int current = get();
        int next = current + 1;
        if (compareAndSet(current, next))
            return next;
    }
}

=== EDIT===

Please talk about this specially in single/core CPUs.

Solution

  • Advantage: no locks, hence no deadlock and generally better scalability

    Disadvantage: risk of starvation (unless the algorithm is also wait-free, but this is generally not the case)

    edit:wait-free algorithms do some operations when it losses CAS race.instead of busytrying/startvation.