/** changes the fork owner if it is dirty, and the other side
* has requested for it. Fork must be locked.
* Returns true if fork moved. false otherwise.
*/
inline bool advance_fork_state_on_lock(size_t forkid,
vertex_id_type source,
vertex_id_type target) {
unsigned char currentowner = forkset[forkid] & OWNER_BIT;
// edge_ids for the request bits
unsigned char my_request_bit = request_bit(currentowner);
unsigned char other_request_bit = request_bit(!currentowner);
bool current_owner_is_eating =
(currentowner == OWNER_SOURCE && philosopherset[source].state == EATING) ||
(currentowner == OWNER_TARGET && philosopherset[target].state == EATING);
bool current_owner_is_hungry =
(currentowner == OWNER_SOURCE && philosopherset[source].state == HUNGRY) ||
(currentowner == OWNER_TARGET && philosopherset[target].state == HUNGRY);
// if the current owner is not eating, and the
// fork is dirty and other side has placed a request
if (current_owner_is_eating == false &&
(forkset[forkid] & DIRTY_BIT) &&
(forkset[forkid] & other_request_bit)) {
// change the owner and clean the fork)
forkset[forkid] = (!currentowner);
if (current_owner_is_hungry) {
forkset[forkid] |= my_request_bit;
}
return true;
}
return false;
}
inline bool advance_fork_state_on_unlock(size_t forkid,
vertex_id_type source,
vertex_id_type target) {
unsigned char currentowner = forkset[forkid] & OWNER_BIT;
// edge_ids for the request bits
unsigned char my_request_bit = request_bit(currentowner);
unsigned char other_request_bit = request_bit(!currentowner);
// if the current owner is not eating, and the
// fork is dirty and other side has placed a request
if ((forkset[forkid] & DIRTY_BIT) &&
(forkset[forkid] & other_request_bit)) {
// change the owner and clean the fork)
// keep my request bit if any
forkset[forkid] = (forkset[forkid] & my_request_bit) | (!currentowner);
return true;
}
return false;
}
/** Places a request for the fork. Requires fork to be locked */
inline void request_for_fork(size_t forkid, bool nextowner) {
forkset[forkid] |= request_bit(nextowner);
}
/** Places a request for the fork. Requires fork to be locked */
inline void request_for_fork(size_t forkid, bool nextowner) {
__sync_fetch_and_or(&forkset[forkid], request_bit(nextowner));
}
