Futures Impl when called recursively with multi-threaded executors can breach continuation chain depth limit

XMLWordPrintableJSON

    • Server Programmability
    • Fully Compatible
    • ALL
    • Programmability 2025-08-18, Programmability 2025-09-01, Programmability 2025-09-15, Programmability 2025-09-29, Programmability 2025-10-13
    • 0
    • None
    • None
    • None
    • None
    • None
    • None
    • None

      When recursing with the futures runtime (example below) using a multi-threaded executor, multiple threads in the executor can race to complete continuations before the "original" invoking thread can collapse the futures chain inside propagateResultTo. This breaches the depth limit inside `transitionToFinished` when run under a debug build, but does not otherwise appear to have correctness impacts.

      Future<T> doWhile(executor, ...) {
  // When this return statement completes, the thread that called
  // doWhile will call propagateResultsTo.
  // But if the executor completes the continuation before propagate
  // completes, the futures chain builds instead of collapsing due
  // to isJustForContinuation.
  // When the iterations are fast enough and the thread pool large
  // enough this temporary chaining breaches the depth limit on
  // future_impl.h:438 
  return executor.schedule([&] {
    return doWhile(executor, ...);
  });
}

            Assignee:
            Mathias Stearn
            Reporter:
            Myles Hathcock (Inactive)
            Votes:
            0 Vote for this issue
            Watchers:
            11 Start watching this issue

              Created:
              Updated:
              Resolved: