Waitfree work stealing is configured with the meson option 'waitfree_work_stealing'.
The retry logic is intentionally left in the Queues and not lifted to the scheduler to reuse the load of an unsuccessful CAS.
Consider the following pseudo code examples:
steal() -> bool: steal() -> res load load loop: if empty return EMPTY if empty return EMPTY cas cas return cas ? STOLEN : LOST_RACE if not WAITFREE and not cas: goto loop outer(): return cas ? STOLEN : LOST_RACE loop: res = steal() outer(): if not WAITFREE and res == LOST_RACE: steal() goto loop
In the right example the value loaded by a possible unsuccessful CAS can not be reused. And a loop of unsuccessful CAS' will result in double loads.
The retries are configurable through a template variable maxRetries.
- maxRetries < 0: indefinitely retries
- maxRetries >= 0: maxRetries