/*
* TransactionLogFetch --- fetch commit status of specified transaction id
*/
static XidStatus
TransactionLogFetch(TransactionId transactionId)
{
XidStatus xidstatus;
/*
* Before going to the commit log manager, check our single item cache to
* see if we didn't just check the transaction status a moment ago.
*/
if (TransactionIdEquals(transactionId, cachedFetchXid))
return cachedFetchXidStatus;
/*
* Also, check to see if the transaction ID is a permanent one.
*/
if (!TransactionIdIsNormal(transactionId))
{
if (TransactionIdEquals(transactionId, BootstrapTransactionId))
return TRANSACTION_STATUS_COMMITTED;
if (TransactionIdEquals(transactionId, FrozenTransactionId))
return TRANSACTION_STATUS_COMMITTED;
return TRANSACTION_STATUS_ABORTED;
}
/*
* Get the transaction status.
*/
xidstatus = TransactionIdGetStatus(transactionId);
/*
* Cache it, but DO NOT cache status for unfinished or sub-committed
* transactions! We only cache status that is guaranteed not to change.
*/
if (xidstatus != TRANSACTION_STATUS_IN_PROGRESS &&
xidstatus != TRANSACTION_STATUS_SUB_COMMITTED)
{
TransactionIdStore(transactionId, &cachedFetchXid);
cachedFetchXidStatus = xidstatus;
}
return xidstatus;
}
/*
* ProcSleep -- put a process to sleep
*
* P() on the semaphore should put us to sleep. The process
* semaphore is cleared by default, so the first time we try
* to acquire it, we sleep.
*
* ASSUME: that no one will fiddle with the queue until after
* we release the spin lock.
*
* NOTES: The process queue is now a priority queue for locking.
*/
int
ProcSleep(PROC_QUEUE *queue,
SPINLOCK spinlock,
int token,
int prio,
LOCK *lock)
{
int i;
PROC *proc;
#ifndef WIN32 /* figure this out later */
struct itimerval timeval, dummy;
#endif /* WIN32 */
proc = (PROC *) MAKE_PTR(queue->links.prev);
for (i=0;i<queue->size;i++)
{
if (proc->prio < prio)
proc = (PROC *) MAKE_PTR(proc->links.prev);
else
break;
}
MyProc->token = token;
MyProc->waitLock = lock;
/* -------------------
* currently, we only need this for the ProcWakeup routines
* -------------------
*/
TransactionIdStore((TransactionId) GetCurrentTransactionId(), &MyProc->xid);
/* -------------------
* assume that these two operations are atomic (because
* of the spinlock).
* -------------------
*/
SHMQueueInsertTL(&(proc->links),&(MyProc->links));
queue->size++;
SpinRelease(spinlock);
/* --------------
* Postgres does not have any deadlock detection code and for this
* reason we must set a timer to wake up the process in the event of
* a deadlock. For now the timer is set for 1 minute and we assume that
* any process which sleeps for this amount of time is deadlocked and will
* receive a SIGALRM signal. The handler should release the processes
* semaphore and abort the current transaction.
*
* Need to zero out struct to set the interval and the micro seconds fields
* to 0.
* --------------
*/
#ifndef WIN32
memset(&timeval, 0, sizeof(struct itimerval));
timeval.it_value.tv_sec = DEADLOCK_TIMEOUT;
if (setitimer(ITIMER_REAL, &timeval, &dummy))
elog(FATAL, "ProcSleep: Unable to set timer for process wakeup");
#endif /* WIN32 */
/* --------------
* if someone wakes us between SpinRelease and IpcSemaphoreLock,
* IpcSemaphoreLock will not block. The wakeup is "saved" by
* the semaphore implementation.
* --------------
*/
IpcSemaphoreLock(MyProc->sem.semId, MyProc->sem.semNum, IpcExclusiveLock);
/* ---------------
* We were awoken before a timeout - now disable the timer
* ---------------
*/
#ifndef WIN32
timeval.it_value.tv_sec = 0;
if (setitimer(ITIMER_REAL, &timeval, &dummy))
elog(FATAL, "ProcSleep: Unable to diable timer for process wakeup");
#endif /* WIN32 */
/* ----------------
* We were assumed to be in a critical section when we went
* to sleep.
* ----------------
*/
SpinAcquire(spinlock);
return(MyProc->errType);
}