WDM_READ
set_bit(WDM_READ, &desc->flags);
set_bit(WDM_READ, &desc->flags);
set_bit(WDM_READ, &desc->flags); /* unblock read */
set_bit(WDM_READ, &desc->flags);
if (!test_bit(WDM_READ, &desc->flags)) {
test_bit(WDM_READ, &desc->flags));
if (!test_bit(WDM_READ, &desc->flags)) { /* lost race */
clear_bit(WDM_READ, &desc->flags);
if (test_bit(WDM_READ, &desc->flags))
clear_bit(WDM_READ, &desc->flags);