/*
* RemoveFirst -- remove the first entry in the free list of ProcGlobal.
*
* Use compare_and_swap to avoid using lock and guarantee atomic operation.
*/
static PGPROC *
RemoveFirst()
{
volatile PROC_HDR *procglobal = ProcGlobal;
SHMEM_OFFSET myOffset;
PGPROC *freeProc = NULL;
/*
* Decrement numFreeProcs before removing the first entry from the
* free list.
*/
gp_atomic_add_32(&procglobal->numFreeProcs, -1);
int32 casResult = false;
while(!casResult)
{
myOffset = procglobal->freeProcs;
if (myOffset == INVALID_OFFSET)
{
break;
}
freeProc = (PGPROC *) MAKE_PTR(myOffset);
casResult = compare_and_swap_ulong(&((PROC_HDR *)procglobal)->freeProcs,
myOffset,
freeProc->links.next);
if (gp_debug_pgproc && !casResult)
{
elog(LOG, "need to retry allocating a PGPROC entry: pid=%d (oldHeadOffset=%ld, newHeadOffset=%ld)",
MyProcPid, myOffset, procglobal->freeProcs);
}
}
if (freeProc == NULL)
{
/*
* Increment numFreeProcs since we didn't remove any entry from
* the free list.
*/
gp_atomic_add_32(&procglobal->numFreeProcs, 1);
}
return freeProc;
}
/*
* Prepend -- prepend the entry to the free list of ProcGlobal.
*
* Use compare_and_swap to avoid using lock and guarantee atomic operation.
*/
static void
Prepend(PGPROC *myProc)
{
int pid = myProc->pid;
myProc->pid = 0;
int32 casResult = false;
/* Update freeProcs atomically. */
while (!casResult)
{
myProc->links.next = ProcGlobal->freeProcs;
casResult = compare_and_swap_ulong(&ProcGlobal->freeProcs,
myProc->links.next,
MAKE_OFFSET(myProc));
if (gp_debug_pgproc && !casResult)
{
elog(LOG, "need to retry moving PGPROC entry to freelist: pid=%d "
"(myOffset=%ld, oldHeadOffset=%ld, newHeadOffset=%ld)",
pid, MAKE_OFFSET(myProc), myProc->links.next, ProcGlobal->freeProcs);
}
}
/* Atomically increment numFreeProcs */
gp_atomic_add_32(&ProcGlobal->numFreeProcs, 1);
}
void ProcNewMppSessionId(int *newSessionId)
{
Assert(newSessionId != NULL);
*newSessionId = MyProc->mppSessionId =
gp_atomic_add_32(&ProcGlobal->mppLocalProcessCounter, 1);
/*
* Make sure that our SessionState entry correctly records our
* new session id.
*/
if (NULL != MySessionState)
{
/* This should not happen outside of dispatcher on the master */
Assert(GpIdentity.segindex == MASTER_CONTENT_ID && Gp_role == GP_ROLE_DISPATCH);
ereport(gp_sessionstate_loglevel, (errmsg("ProcNewMppSessionId: changing session id (old: %d, new: %d), pinCount: %d, activeProcessCount: %d",
MySessionState->sessionId, *newSessionId, MySessionState->pinCount, MySessionState->activeProcessCount), errprintstack(true)));
#ifdef USE_ASSERT_CHECKING
MySessionState->isModifiedSessionId = true;
#endif
MySessionState->sessionId = *newSessionId;
}
}
/*
* Updates the given performance counter by delta
*
* delta can be positive or negative
*/
void
Cache_UpdatePerfCounter(uint32 *counter, int delta)
{
Assert(counter + delta >= 0);
gp_atomic_add_32((int32 *) counter, delta);
}
/*
* Marks the current process as clean. If all the processes are marked
* as clean for this session (i.e., cleanupCountdown == 0 in the
* MySessionState) then we reset session's runaway status as well as
* the runaway detector flag (i.e., a new runaway detector can run).
*
* Parameters:
* ignoredCleanup: whether the cleanup was ignored, i.e., no elog(ERROR, ...)
* was thrown. In such case a deactivated process is not reactivated as the
* deactivation didn't get interrupted.
*/
void
RunawayCleaner_RunawayCleanupDoneForProcess(bool ignoredCleanup)
{
/*
* We don't do anything if we don't have an ongoing cleanup, or we already finished
* cleanup once for the current runaway event
*/
if (beginCleanupRunawayVersion != *latestRunawayVersion ||
endCleanupRunawayVersion == beginCleanupRunawayVersion)
{
/* Either we never started cleanup, or we already finished */
return;
}
/* Disable repeating call */
endCleanupRunawayVersion = beginCleanupRunawayVersion;
Assert(NULL != MySessionState);
/*
* As the current cleanup holds leverage on the cleanupCountdown,
* the session must stay as runaway at least until the current
* process marks itself clean
*/
Assert(MySessionState->runawayStatus != RunawayStatus_NotRunaway);
/* We only cleanup if we were active when the runaway event happened */
Assert((!isProcessActive && *latestRunawayVersion < deactivationVersion &&
*latestRunawayVersion > activationVersion) ||
(*latestRunawayVersion > activationVersion &&
(activationVersion >= deactivationVersion && isProcessActive)));
/*
* We don't reactivate if the process is already active or a deactivated
* process never errored out during deactivation (i.e., failed to complete
* deactivation)
*/
if (!isProcessActive && !ignoredCleanup)
{
Assert(1 == *isRunawayDetector);
Assert(0 < MySessionState->cleanupCountdown);
/*
* As the process threw ERROR instead of going into ReadCommand() blocking
* state, we have to reactivate the process from its current Deactivated
* state
*/
IdleTracker_ActivateProcess();
}
Assert(0 < MySessionState->cleanupCountdown);
#if USE_ASSERT_CHECKING
int cleanProgress =
#endif
gp_atomic_add_32(&MySessionState->cleanupCountdown, -1);
Assert(0 <= cleanProgress);
bool finalCleaner = compare_and_swap_32((uint32*) &MySessionState->cleanupCountdown,
0, CLEANUP_COUNTDOWN_BEFORE_RUNAWAY);
if (finalCleaner)
{
/*
* The final cleaner is responsible to reset the runaway flag,
* and enable the runaway detection process.
*/
RunawayCleaner_RunawayCleanupDoneForSession();
}
/*
* Finally we are done with all critical cleanup, which includes releasing all our memory and
* releasing our cleanup counter so that another session can be marked as runaway, if needed.
* Now, we have some head room to actually record our usage.
*/
write_stderr("Logging memory usage because of runaway cleanup. Note, this is a post-cleanup logging and may be incomplete.");
MemoryAccounting_SaveToLog();
MemoryContextStats(TopMemoryContext);
}
/*
* InitProcess -- initialize a per-process data structure for this backend
*/
void
InitProcess(void)
{
/* use volatile pointer to prevent code rearrangement */
volatile PROC_HDR *procglobal = ProcGlobal;
int i;
/*
* ProcGlobal should be set up already (if we are a backend, we inherit
* this by fork() or EXEC_BACKEND mechanism from the postmaster).
*/
if (procglobal == NULL)
elog(PANIC, "proc header uninitialized");
if (MyProc != NULL)
elog(ERROR, "you already exist");
MyProc = RemoveFirst();
if (MyProc == NULL)
{
ereport(FATAL,
(errcode(ERRCODE_TOO_MANY_CONNECTIONS),
errmsg("sorry, too many clients already")));
}
if (gp_debug_pgproc)
{
elog(LOG, "allocating PGPROC entry for pid %d, freeProcs (prev offset, new offset): (%ld, %ld)",
MyProcPid, MAKE_OFFSET(MyProc), MyProc->links.next);
}
set_spins_per_delay(procglobal->spins_per_delay);
int mppLocalProcessSerial = gp_atomic_add_32(&procglobal->mppLocalProcessCounter, 1);
lockHolderProcPtr = MyProc;
/* Set the next pointer to INVALID_OFFSET */
MyProc->links.next = INVALID_OFFSET;
/*
* Initialize all fields of MyProc, except for the semaphore which was
* prepared for us by InitProcGlobal.
*/
SHMQueueElemInit(&(MyProc->links));
MyProc->waitStatus = STATUS_OK;
MyProc->xid = InvalidTransactionId;
MyProc->xmin = InvalidTransactionId;
MyProc->pid = MyProcPid;
/* databaseId and roleId will be filled in later */
MyProc->databaseId = InvalidOid;
MyProc->roleId = InvalidOid;
MyProc->inVacuum = false;
MyProc->postmasterResetRequired = true;
MyProc->lwWaiting = false;
MyProc->lwExclusive = false;
MyProc->lwWaitLink = NULL;
MyProc->waitLock = NULL;
MyProc->waitProcLock = NULL;
for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
SHMQueueInit(&(MyProc->myProcLocks[i]));
/*
* mppLocalProcessSerial uniquely identifies this backend process among
* all those that our parent postmaster process creates over its lifetime.
*
* Since we use the process serial number to decide if we should
* deliver a response from a server under this spin, we need to
* assign it under the spin lock.
*/
MyProc->mppLocalProcessSerial = mppLocalProcessSerial;
/*
* A nonzero gp_session_id uniquely identifies an MPP client session
* over the lifetime of the entry postmaster process. A qDisp passes
* its gp_session_id down to all of its qExecs. If this is a qExec,
* we have already received the gp_session_id from the qDisp.
*/
elog(DEBUG1,"InitProcess(): gp_session_id %d", gp_session_id);
if (Gp_role == GP_ROLE_DISPATCH && gp_session_id == -1)
gp_session_id = mppLocalProcessSerial;
MyProc->mppSessionId = gp_session_id;
MyProc->mppIsWriter = Gp_is_writer;
/*
* We might be reusing a semaphore that belonged to a failed process. So
* be careful and reinitialize its value here. (This is not strictly
* necessary anymore, but seems like a good idea for cleanliness.)
*/
PGSemaphoreReset(&MyProc->sem);
/* Set wait portal (do not check if resource scheduling is enabled) */
MyProc->waitPortalId = INVALID_PORTALID;
MyProc->queryCommandId = -1;
/*
* Arrange to clean up at backend exit.
*/
on_shmem_exit(ProcKill, 0);
/*
* Now that we have a PGPROC, we could try to acquire locks, so initialize
* the deadlock checker.
*/
InitDeadLockChecking();
}