static StgBool validate_and_acquire_ownership()

in rts/STM.c [755:808]

• 50 lines of code
• 12 McCabe index (conditional complexity)

static StgBool validate_and_acquire_ownership (Capability *cap,
                                               StgTRecHeader *trec,
                                               int acquire_all,
                                               int retain_ownership) {
  StgBool result;

  if (shake()) {
    TRACE("%p : shake, pretending trec is invalid when it may not be", trec);
    return false;
  }

  ASSERT((trec -> state == TREC_ACTIVE) ||
         (trec -> state == TREC_WAITING) ||
         (trec -> state == TREC_CONDEMNED));
  result = !((trec -> state) == TREC_CONDEMNED);
  if (result) {
    FOR_EACH_ENTRY(trec, e, {
      StgTVar *s;
      s = e -> tvar;
      if (acquire_all || entry_is_update(e)) {
        TRACE("%p : trying to acquire %p", trec, s);
        if (!cond_lock_tvar(trec, s, e -> expected_value)) {
          TRACE("%p : failed to acquire %p", trec, s);
          result = false;
          BREAK_FOR_EACH;
        }
      } else {
        ASSERT(config_use_read_phase);
        IF_STM_FG_LOCKS({
          TRACE("%p : will need to check %p", trec, s);
          if (s -> current_value != e -> expected_value) {
            TRACE("%p : doesn't match", trec);
            result = false;
            BREAK_FOR_EACH;
          }
          e -> num_updates = s -> num_updates;
          if (s -> current_value != e -> expected_value) {
            TRACE("%p : doesn't match (race)", trec);
            result = false;
            BREAK_FOR_EACH;
          } else {
            TRACE("%p : need to check version %ld", trec, e -> num_updates);
          }
        });
      }
    });
  }

  if ((!result) || (!retain_ownership)) {
      revert_ownership(cap, trec, acquire_all);
  }

  return result;
}