/*
* ReceiveSharedInvalidMessages
* Process shared-cache-invalidation messages waiting for this backend
*
* We guarantee to process all messages that had been queued before the
* routine was entered. It is of course possible for more messages to get
* queued right after our last SIGetDataEntries call.
*
* NOTE: it is entirely possible for this routine to be invoked recursively
* as a consequence of processing inside the invalFunction or resetFunction.
* Furthermore, such a recursive call must guarantee that all outstanding
* inval messages have been processed before it exits. This is the reason
* for the strange-looking choice to use a statically allocated buffer array
* and counters; it's so that a recursive call can process messages already
* sucked out of sinvaladt.c.
*/
void
ReceiveSharedInvalidMessages(
void (*invalFunction) (SharedInvalidationMessage *msg),
void (*resetFunction) (void))
{
#define MAXINVALMSGS 32
static SharedInvalidationMessage messages[MAXINVALMSGS];
/*
* We use volatile here to prevent bugs if a compiler doesn't realize that
* recursion is a possibility ...
*/
static volatile int nextmsg = 0;
static volatile int nummsgs = 0;
/* Deal with any messages still pending from an outer recursion */
while (nextmsg < nummsgs)
{
SharedInvalidationMessage *msg = &messages[nextmsg++];
invalFunction(msg);
}
do
{
int getResult;
nextmsg = nummsgs = 0;
/* Try to get some more messages */
getResult = SIGetDataEntries(messages, MAXINVALMSGS);
if (getResult < 0)
{
/* got a reset message */
elog(DEBUG4, "cache state reset");
resetFunction();
break; /* nothing more to do */
}
/* Process them, being wary that a recursive call might eat some */
nextmsg = 0;
nummsgs = getResult;
while (nextmsg < nummsgs)
{
SharedInvalidationMessage *msg = &messages[nextmsg++];
invalFunction(msg);
}
/*
* We only need to loop if the last SIGetDataEntries call (which might
* have been within a recursive call) returned a full buffer.
*/
} while (nummsgs == MAXINVALMSGS);
/*
* We are now caught up. If we received a catchup signal, reset that
* flag, and call SICleanupQueue(). This is not so much because we need
* to flush dead messages right now, as that we want to pass on the
* catchup signal to the next slowest backend. "Daisy chaining" the
* catchup signal this way avoids creating spikes in system load for what
* should be just a background maintenance activity.
*/
if (catchupInterruptOccurred)
{
catchupInterruptOccurred = 0;
elog(DEBUG4, "sinval catchup complete, cleaning queue");
SICleanupQueue(false, 0);
}
}
/*
* SIInsertDataEntries
* Add new invalidation message(s) to the buffer.
*/
void
SIInsertDataEntries(const SharedInvalidationMessage *data, int n)
{
SISeg *segP = shmInvalBuffer;
/*
* N can be arbitrarily large. We divide the work into groups of no more
* than WRITE_QUANTUM messages, to be sure that we don't hold the lock for
* an unreasonably long time. (This is not so much because we care about
* letting in other writers, as that some just-caught-up backend might be
* trying to do SICleanupQueue to pass on its signal, and we don't want it
* to have to wait a long time.) Also, we need to consider calling
* SICleanupQueue every so often.
*/
while (n > 0)
{
int nthistime = Min(n, WRITE_QUANTUM);
int numMsgs;
int max;
n -= nthistime;
LWLockAcquire(SInvalWriteLock, LW_EXCLUSIVE);
/*
* If the buffer is full, we *must* acquire some space. Clean the
* queue and reset anyone who is preventing space from being freed.
* Otherwise, clean the queue only when it's exceeded the next
* fullness threshold. We have to loop and recheck the buffer state
* after any call of SICleanupQueue.
*/
for (;;)
{
numMsgs = segP->maxMsgNum - segP->minMsgNum;
if (numMsgs + nthistime > MAXNUMMESSAGES ||
numMsgs >= segP->nextThreshold)
SICleanupQueue(true, nthistime);
else
break;
}
/*
* Insert new message(s) into proper slot of circular buffer
*/
max = segP->maxMsgNum;
while (nthistime-- > 0)
{
segP->buffer[max % MAXNUMMESSAGES] = *data++;
max++;
}
/* Update current value of maxMsgNum using spinlock */
{
/* use volatile pointer to prevent code rearrangement */
volatile SISeg *vsegP = segP;
SpinLockAcquire(&vsegP->msgnumLock);
vsegP->maxMsgNum = max;
SpinLockRelease(&vsegP->msgnumLock);
}
LWLockRelease(SInvalWriteLock);
}
}
/*
* SIInsertDataEntries
* Add new invalidation message(s) to the buffer.
*/
void
SIInsertDataEntries(const SharedInvalidationMessage *data, int n)
{
SISeg *segP = shmInvalBuffer;
/*
* N can be arbitrarily large. We divide the work into groups of no more
* than WRITE_QUANTUM messages, to be sure that we don't hold the lock for
* an unreasonably long time. (This is not so much because we care about
* letting in other writers, as that some just-caught-up backend might be
* trying to do SICleanupQueue to pass on its signal, and we don't want it
* to have to wait a long time.) Also, we need to consider calling
* SICleanupQueue every so often.
*/
while (n > 0)
{
int nthistime = Min(n, WRITE_QUANTUM);
int numMsgs;
int max;
int i;
n -= nthistime;
LWLockAcquire(SInvalWriteLock, LW_EXCLUSIVE);
/*
* If the buffer is full, we *must* acquire some space. Clean the
* queue and reset anyone who is preventing space from being freed.
* Otherwise, clean the queue only when it's exceeded the next
* fullness threshold. We have to loop and recheck the buffer state
* after any call of SICleanupQueue.
*/
for (;;)
{
numMsgs = segP->maxMsgNum - segP->minMsgNum;
if (numMsgs + nthistime > MAXNUMMESSAGES ||
numMsgs >= segP->nextThreshold)
SICleanupQueue(true, nthistime);
else
break;
}
/*
* Insert new message(s) into proper slot of circular buffer
*/
max = segP->maxMsgNum;
while (nthistime-- > 0)
{
segP->buffer[max % MAXNUMMESSAGES] = *data++;
max++;
}
/* Update current value of maxMsgNum using spinlock */
SpinLockAcquire(&segP->msgnumLock);
segP->maxMsgNum = max;
SpinLockRelease(&segP->msgnumLock);
/*
* Now that the maxMsgNum change is globally visible, we give everyone
* a swift kick to make sure they read the newly added messages.
* Releasing SInvalWriteLock will enforce a full memory barrier, so
* these (unlocked) changes will be committed to memory before we exit
* the function.
*/
for (i = 0; i < segP->lastBackend; i++)
{
ProcState *stateP = &segP->procState[i];
stateP->hasMessages = true;
}
LWLockRelease(SInvalWriteLock);
}
}
