int odp_ticketlock_trylock(odp_ticketlock_t *tklock)
{
/* We read 'next_ticket' and 'cur_ticket' non-atomically which should
* not be a problem as they are not independent of each other.
* 'cur_ticket' is always <= to 'next_ticket' and if we see an
* older value of 'cur_ticket', this only means the lock will
* look busy and trylock will fail. */
uint32_t next = odp_atomic_load_u32(&tklock->next_ticket);
uint32_t cur = odp_atomic_load_u32(&tklock->cur_ticket);
/* First check that lock is available and possible to take without
* spinning. */
if (next == cur) {
/* Then try to take the lock by incrementing 'next_ticket'
* but only if it still has the original value which is
* equal to 'cur_ticket'.
* We don't have to include 'cur_ticket' in the comparison
* because it cannot be larger than 'next_ticket' (only
* smaller if the lock is busy).
* If CAS fails, it means some other thread intercepted and
* took a ticket which means the lock is not available
* anymore */
if (odp_atomic_cas_acq_u32(&tklock->next_ticket,
&next, next + 1))
return 1;
}
return 0;
}
void odp_rwlock_read_lock(odp_rwlock_t *rwlock)
{
uint32_t cnt;
int is_locked = 0;
while (is_locked == 0) {
cnt = odp_atomic_load_u32(&rwlock->cnt);
/* waiting for read lock */
if ((int32_t)cnt < 0) {
odp_cpu_pause();
continue;
}
is_locked = odp_atomic_cas_acq_u32(&rwlock->cnt,
&cnt, cnt + 1);
}
}
void odp_rwlock_write_lock(odp_rwlock_t *rwlock)
{
uint32_t cnt;
int is_locked = 0;
while (is_locked == 0) {
uint32_t zero = 0;
cnt = odp_atomic_load_u32(&rwlock->cnt);
/* lock acquired, wait */
if (cnt != 0) {
odp_cpu_pause();
continue;
}
is_locked = odp_atomic_cas_acq_u32(&rwlock->cnt,
&zero, (uint32_t)-1);
}
}
