PR_GROWING
if (pp->pr_flags & PR_GROWING) {
} while (pp->pr_flags & PR_GROWING);
pp->pr_flags |= PR_GROWING;
KASSERT(pp->pr_flags & PR_GROWING);
pp->pr_flags &= ~(PR_GROWING|PR_GROWINGNOWAIT);
KASSERT(pp->pr_flags & PR_GROWING);
pp->pr_flags &= ~(PR_GROWING|PR_GROWINGNOWAIT);