/*
* Store a word-sized value in a unit transaction.
*/
static INLINE int
stm_unit_write(volatile stm_word_t *addr, stm_word_t value, stm_word_t mask, stm_word_t *timestamp)
{
#ifdef UNIT_TX
volatile stm_word_t *lock;
stm_word_t l;
PRINT_DEBUG2("==> stm_unit_write(a=%p,d=%p-%lu,m=0x%lx)\n",
addr, (void *)value, (unsigned long)value, (unsigned long)mask);
/* Get reference to lock */
lock = GET_LOCK(addr);
/* Try to acquire lock */
restart:
l = ATOMIC_LOAD_ACQ(lock);
if (LOCK_GET_OWNED(l)) {
/* Locked: wait until lock is free */
#ifdef WAIT_YIELD
sched_yield();
#endif /* WAIT_YIELD */
goto restart;
}
/* Not locked */
if (timestamp != NULL && LOCK_GET_TIMESTAMP(l) > *timestamp) {
/* Return current timestamp */
*timestamp = LOCK_GET_TIMESTAMP(l);
return 0;
}
/* TODO: would need to store thread ID to be able to kill it (for wait freedom) */
if (ATOMIC_CAS_FULL(lock, l, LOCK_UNIT) == 0)
goto restart;
ATOMIC_STORE(addr, value);
/* Update timestamp with newer value (may exceed VERSION_MAX by up to MAX_THREADS) */
l = FETCH_INC_CLOCK + 1;
if (timestamp != NULL)
*timestamp = l;
/* Make sure that lock release becomes visible */
ATOMIC_STORE_REL(lock, LOCK_SET_TIMESTAMP(l));
if (unlikely(l >= VERSION_MAX)) {
/* Block all transactions and reset clock (current thread is not in active transaction) */
stm_quiesce_barrier(NULL, rollover_clock, NULL);
}
return 1;
#else /* ! UNIT_TX */
fprintf(stderr, "Unit transaction is not enabled\n");
exit(-1);
return 1;
#endif /* ! UNIT_TX */
}
/*
* Initialize the transaction descriptor before start or restart.
*/
static inline void stm_prepare(stm_tx_t *tx)
{
start:
/* Start timestamp */
tx->start = tx->end = GET_CLOCK; /* OPT: Could be delayed until first read/write */
/* Allow extensions */
tx->can_extend = 1;
if (tx->start >= VERSION_MAX) {
/* Block all transactions and reset clock */
stm_quiesce_barrier(tx, rollover_clock, NULL);
goto start;
}
/* Read/write set */
tx->w_set.has_writes = 0;
tx->w_set.nb_entries = 0;
tx->r_set.nb_entries = 0;
/* Set status */
UPDATE_STATUS(tx->status, TX_ACTIVE);
stm_check_quiesce(tx);
}