SIGFASTBLOCK_INC
atomic_add_32(&curthread->fsigblock, SIGFASTBLOCK_INC);
oldval = atomic_fetchadd_32(&curthread->fsigblock, -SIGFASTBLOCK_INC);
if (oldval == (SIGFASTBLOCK_PEND | SIGFASTBLOCK_INC))
assert((fsigblock & ~SIGFASTBLOCK_FLAGS) >= SIGFASTBLOCK_INC);
oldval = atomic_fetchadd_32(&fsigblock, -SIGFASTBLOCK_INC);
if (oldval == (SIGFASTBLOCK_PEND | SIGFASTBLOCK_INC))
atomic_add_32(&fsigblock, SIGFASTBLOCK_INC);