Checkpoints and continuations instead of nested transactions

We present a mechanism for partially aborting transactions through the use of data structure checkpoints and control-flow continuations. In particular, we show that boosted transactions [9] already have built-in restoration points and afford a simple, efficient implementation. Our mechanism is far simpler than previous work, which relied on complex nesting schemes to establish checkpoints. We demonstrate syntactic advantages and we quantify the overhead of checkpoints and explore several examples, illustrating the utility of partially aborting transactions. We additionally present a novel queue-based spin lock which allows threads to timeout and differ in priority. Unlike the known lock due to Craig [5], our lock is more efficient for priority schemes of few levels.