C++ HOLD_INTERRUPTS函数代码示例

/*
 * pl_ist_reset - Abort the given number of ISTs and set a Python error.
 *
 * Used to handle cases where a code object fails to resolve open transactions.
 */
void
pl_ist_reset(unsigned long count)
{
	HOLD_INTERRUPTS();
	for (; count > 0; --count)
		RollbackAndReleaseCurrentSubTransaction();
	RESUME_INTERRUPTS();
}

/*
 * Cancel any pending wait for lock, when aborting a transaction, and revert
 * any strong lock count acquisition for a lock being acquired.
 *
 * (Normally, this would only happen if we accept a cancel/die
 * interrupt while waiting; but an ereport(ERROR) before or during the lock
 * wait is within the realm of possibility, too.)
 */
void
LockErrorCleanup(void)
{
	LWLock	   *partitionLock;
	DisableTimeoutParams timeouts[2];

	HOLD_INTERRUPTS();

	AbortStrongLockAcquire();

	/* Nothing to do if we weren't waiting for a lock */
	if (lockAwaited == NULL)
	{
		RESUME_INTERRUPTS();
		return;
	}

	/*
	 * Turn off the deadlock and lock timeout timers, if they are still
	 * running (see ProcSleep).  Note we must preserve the LOCK_TIMEOUT
	 * indicator flag, since this function is executed before
	 * ProcessInterrupts when responding to SIGINT; else we'd lose the
	 * knowledge that the SIGINT came from a lock timeout and not an external
	 * source.
	 */
	timeouts[0].id = DEADLOCK_TIMEOUT;
	timeouts[0].keep_indicator = false;
	timeouts[1].id = LOCK_TIMEOUT;
	timeouts[1].keep_indicator = true;
	disable_timeouts(timeouts, 2);

	/* Unlink myself from the wait queue, if on it (might not be anymore!) */
	partitionLock = LockHashPartitionLock(lockAwaited->hashcode);
	LWLockAcquire(partitionLock, LW_EXCLUSIVE);

	if (MyProc->links.next != NULL)
	{
		/* We could not have been granted the lock yet */
		RemoveFromWaitQueue(MyProc, lockAwaited->hashcode);
	}
	else
	{
		/*
		 * Somebody kicked us off the lock queue already.  Perhaps they
		 * granted us the lock, or perhaps they detected a deadlock. If they
		 * did grant us the lock, we'd better remember it in our local lock
		 * table.
		 */
		if (MyProc->waitStatus == STATUS_OK)
			GrantAwaitedLock();
	}

	lockAwaited = NULL;

	LWLockRelease(partitionLock);

	RESUME_INTERRUPTS();
}

/*
 * LWLockConditionalAcquire - acquire a lightweight lock in the specified mode
 *
 * If the lock is not available, return FALSE with no side-effects.
 *
 * If successful, cancel/die interrupts are held off until lock release.
 */
bool
LWLockConditionalAcquire(LWLockId lockid, LWLockMode mode)
{
	volatile LWLock *lock = LWLockArray + lockid;
	bool		mustwait;

	PRINT_LWDEBUG("LWLockConditionalAcquire", lockid, lock);

	/*
	 * Lock out cancel/die interrupts until we exit the code section
	 * protected by the LWLock.  This ensures that interrupts will not
	 * interfere with manipulations of data structures in shared memory.
	 */
	HOLD_INTERRUPTS();

	/* Acquire mutex.  Time spent holding mutex should be short! */
	SpinLockAcquire_NoHoldoff(&lock->mutex);

	/* If I can get the lock, do so quickly. */
	if (mode == LW_EXCLUSIVE)
	{
		if (lock->exclusive == 0 && lock->shared == 0)
		{
			lock->exclusive++;
			mustwait = false;
		}
		else
			mustwait = true;
	}
	else
	{
		if (lock->exclusive == 0)
		{
			lock->shared++;
			mustwait = false;
		}
		else
			mustwait = true;
	}

	/* We are done updating shared state of the lock itself. */
	SpinLockRelease_NoHoldoff(&lock->mutex);

	if (mustwait)
	{
		/* Failed to get lock, so release interrupt holdoff */
		RESUME_INTERRUPTS();
		LOG_LWDEBUG("LWLockConditionalAcquire", lockid, "failed");
	}
	else
	{
		/* Add lock to list of locks held by this backend */
		Assert(num_held_lwlocks < MAX_SIMUL_LWLOCKS);
		held_lwlocks[num_held_lwlocks++] = lockid;
	}

	return !mustwait;
}

/*
 * LWLockReleaseAll - release all currently-held locks
 *
 * Used to clean up after ereport(ERROR). An important difference between this
 * function and retail LWLockRelease calls is that InterruptHoldoffCount is
 * unchanged by this operation.  This is necessary since InterruptHoldoffCount
 * has been set to an appropriate level earlier in error recovery. We could
 * decrement it below zero if we allow it to drop for each released lock!
 */
void
LWLockReleaseAll(void)
{
	while (num_held_lwlocks > 0)
	{
		HOLD_INTERRUPTS();		/* match the upcoming RESUME_INTERRUPTS */

		LWLockRelease(held_lwlocks[num_held_lwlocks - 1]);
	}
}

/*
 * Report a COMMERROR.
 *
 * This function holds an interrupt before reporting this error to avoid
 * a self deadlock situation, see MPP-13718 for more info.
 */
static void
report_commerror(const char *err_msg)
{
	HOLD_INTERRUPTS();

	ereport(COMMERROR,
			(errcode(ERRCODE_PROTOCOL_VIOLATION),
			 errmsg("%s",err_msg)));

	RESUME_INTERRUPTS();
}

inline
void
AbstractionLayer::Allocator::free(void *inPtr) const {
    if (inPtr == NULL)
        return;
        
    /*
     * See allocate(const size_t, const std::nothrow_t&) why we disable
     * processing of interrupts.
     */
    HOLD_INTERRUPTS();
    PG_TRY(); {
        pfree(unaligned(inPtr));
    } PG_CATCH(); {
        FlushErrorState();
    } PG_END_TRY();
    RESUME_INTERRUPTS();
}

void
FileRepSubProcess_Main()
{
	const char *statmsg;

	MemoryContext fileRepSubProcessMemoryContext;

	sigjmp_buf	local_sigjmp_buf;

	MyProcPid = getpid();

	MyStartTime = time(NULL);

	/*
	 * Create a PGPROC so we can use LWLocks in FileRep sub-processes.  The
	 * routine also register clean up at process exit
	 */
	InitAuxiliaryProcess();

	InitBufferPoolBackend();

	FileRepSubProcess_ConfigureSignals();

	/*
	 * If an exception is encountered, processing resumes here.
	 *
	 * See notes in postgres.c about the design of this coding.
	 */
	if (sigsetjmp(local_sigjmp_buf, 1) != 0)
	{
		/* Prevents interrupts while cleaning up */
		HOLD_INTERRUPTS();

		/* Report the error to the server log */
		EmitErrorReport();

		LWLockReleaseAll();

		if (FileRepPrimary_IsResyncManagerOrWorker())
		{
			LockReleaseAll(DEFAULT_LOCKMETHOD, false);
		}

		if (FileRepIsBackendSubProcess(fileRepProcessType))
		{
			AbortBufferIO();
			UnlockBuffers();

			/* buffer pins are released here: */
			ResourceOwnerRelease(CurrentResourceOwner,
								 RESOURCE_RELEASE_BEFORE_LOCKS,
								 false, true);
		}

		/*
		 * We can now go away.	Note that because we'll call InitProcess, a
		 * callback will be registered to do ProcKill, which will clean up
		 * necessary state.
		 */
		proc_exit(0);
	}

	/* We can now handle ereport(ERROR) */
	PG_exception_stack = &local_sigjmp_buf;

	PG_SETMASK(&UnBlockSig);

	/*
	 * Identify myself via ps
	 */

	statmsg = FileRepProcessTypeToString[fileRepProcessType];

	init_ps_display(statmsg, "", "", "");

	/* Create the memory context where cross-transaction state is stored */
	fileRepSubProcessMemoryContext = AllocSetContextCreate(TopMemoryContext,
														   "filerep subprocess memory context",
														   ALLOCSET_DEFAULT_MINSIZE,
														   ALLOCSET_DEFAULT_INITSIZE,
														   ALLOCSET_DEFAULT_MAXSIZE);

	MemoryContextSwitchTo(fileRepSubProcessMemoryContext);

	stateChangeRequestCounter++;

	FileRepSubProcess_ProcessSignals();

	switch (fileRepProcessType)
	{
		case FileRepProcessTypePrimarySender:
			FileRepPrimary_StartSender();
			break;

		case FileRepProcessTypeMirrorReceiver:
			FileRepMirror_StartReceiver();
			break;

		case FileRepProcessTypeMirrorConsumer:
		case FileRepProcessTypeMirrorConsumerWriter:
//.........这里部分代码省略.........

/*
 * Main entry point for checkpointer process
 *
 * This is invoked from AuxiliaryProcessMain, which has already created the
 * basic execution environment, but not enabled signals yet.
 */
void
CheckpointerMain(void)
{
	sigjmp_buf	local_sigjmp_buf;
	MemoryContext checkpointer_context;

	CheckpointerShmem->checkpointer_pid = MyProcPid;

	/*
	 * Properly accept or ignore signals the postmaster might send us
	 *
	 * Note: we deliberately ignore SIGTERM, because during a standard Unix
	 * system shutdown cycle, init will SIGTERM all processes at once.  We
	 * want to wait for the backends to exit, whereupon the postmaster will
	 * tell us it's okay to shut down (via SIGUSR2).
	 */
	pqsignal(SIGHUP, ChkptSigHupHandler);		/* set flag to read config
												 * file */
	pqsignal(SIGINT, ReqCheckpointHandler);		/* request checkpoint */
	pqsignal(SIGTERM, SIG_IGN); /* ignore SIGTERM */
	pqsignal(SIGQUIT, chkpt_quickdie);	/* hard crash time */
	pqsignal(SIGALRM, SIG_IGN);
	pqsignal(SIGPIPE, SIG_IGN);
	pqsignal(SIGUSR1, chkpt_sigusr1_handler);
	pqsignal(SIGUSR2, ReqShutdownHandler);		/* request shutdown */

	/*
	 * Reset some signals that are accepted by postmaster but not here
	 */
	pqsignal(SIGCHLD, SIG_DFL);
	pqsignal(SIGTTIN, SIG_DFL);
	pqsignal(SIGTTOU, SIG_DFL);
	pqsignal(SIGCONT, SIG_DFL);
	pqsignal(SIGWINCH, SIG_DFL);

	/* We allow SIGQUIT (quickdie) at all times */
	sigdelset(&BlockSig, SIGQUIT);

	/*
	 * Initialize so that first time-driven event happens at the correct time.
	 */
	last_checkpoint_time = last_xlog_switch_time = (pg_time_t) time(NULL);

	/*
	 * Create a resource owner to keep track of our resources (currently only
	 * buffer pins).
	 */
	CurrentResourceOwner = ResourceOwnerCreate(NULL, "Checkpointer");

	/*
	 * Create a memory context that we will do all our work in.  We do this so
	 * that we can reset the context during error recovery and thereby avoid
	 * possible memory leaks.  Formerly this code just ran in
	 * TopMemoryContext, but resetting that would be a really bad idea.
	 */
	checkpointer_context = AllocSetContextCreate(TopMemoryContext,
												 "Checkpointer",
												 ALLOCSET_DEFAULT_SIZES);
	MemoryContextSwitchTo(checkpointer_context);

	/*
	 * If an exception is encountered, processing resumes here.
	 *
	 * See notes in postgres.c about the design of this coding.
	 */
	if (sigsetjmp(local_sigjmp_buf, 1) != 0)
	{
		/* Since not using PG_TRY, must reset error stack by hand */
		error_context_stack = NULL;

		/* Prevent interrupts while cleaning up */
		HOLD_INTERRUPTS();

		/* Report the error to the server log */
		EmitErrorReport();

		/*
		 * These operations are really just a minimal subset of
		 * AbortTransaction().  We don't have very many resources to worry
		 * about in checkpointer, but we do have LWLocks, buffers, and temp
		 * files.
		 */
		LWLockReleaseAll();
		ConditionVariableCancelSleep();
		pgstat_report_wait_end();
		AbortBufferIO();
		UnlockBuffers();
		/* buffer pins are released here: */
		ResourceOwnerRelease(CurrentResourceOwner,
							 RESOURCE_RELEASE_BEFORE_LOCKS,
							 false, true);
		/* we needn't bother with the other ResourceOwnerRelease phases */
		AtEOXact_Buffers(false);
		AtEOXact_SMgr();
//.........这里部分代码省略.........

void
CdbCheckDispatchResult_internal(struct CdbDispatcherState *ds,
								struct SegmentDatabaseDescriptor ***failedSegDB,
								int *numOfFailed, DispatchWaitMode waitMode)
{
	int	i;
	int	j;
	int	nFailed = 0;
	DispatchCommandParms *pParms;
	CdbDispatchResult *dispatchResult;
	SegmentDatabaseDescriptor *segdbDesc;

	Assert(ds != NULL);

	if (failedSegDB)
		*failedSegDB = NULL;
	if (numOfFailed)
		*numOfFailed = 0;

	/*
	 * No-op if no work was dispatched since the last time we were called.
	 */
	if (!ds->dispatchThreads || ds->dispatchThreads->threadCount == 0)
	{
		elog(DEBUG5, "CheckDispatchResult: no threads active");
		return;
	}

	/*
	 * Wait for threads to finish.
	 */
	for (i = 0; i < ds->dispatchThreads->threadCount; i++)
	{
		pParms = &ds->dispatchThreads->dispatchCommandParmsAr[i];
		Assert(pParms != NULL);

		/*
		 * Does caller want to stop short?
		 */
		switch (waitMode)
		{
			case DISPATCH_WAIT_CANCEL:
			case DISPATCH_WAIT_FINISH:
				pParms->waitMode = waitMode;
				break;
			default:
				break;
		}

		if (gp_connections_per_thread == 0)
		{
			thread_DispatchWait(pParms);
		}
		else
		{
			elog(DEBUG4, "CheckDispatchResult: Joining to thread %d of %d",
				 i + 1, ds->dispatchThreads->threadCount);

			if (pParms->thread_valid)
			{
				int			pthread_err = 0;

				pthread_err = pthread_join(pParms->thread, NULL);
				if (pthread_err != 0)
					elog(FATAL,
						 "CheckDispatchResult: pthread_join failed on thread %d (%lu) of %d (returned %d attempting to join to %lu)",
						 i + 1,
#ifndef _WIN32
						 (unsigned long) pParms->thread,
#else
						 (unsigned long) pParms->thread.p,
#endif
						 ds->dispatchThreads->threadCount, pthread_err,
						 (unsigned long) mythread());
			}
		}
		HOLD_INTERRUPTS();
		pParms->thread_valid = false;
		MemSet(&pParms->thread, 0, sizeof(pParms->thread));
		RESUME_INTERRUPTS();

		/*
		 * Examine the CdbDispatchResult objects containing the results
		 * from this thread's QEs.
		 */
		for (j = 0; j < pParms->db_count; j++)
		{
			dispatchResult = pParms->dispatchResultPtrArray[j];

			if (dispatchResult == NULL)
			{
				elog(LOG, "CheckDispatchResult: result object is NULL ? skipping.");
				continue;
			}

			if (dispatchResult->segdbDesc == NULL)
			{
				elog(LOG, "CheckDispatchResult: result object segment descriptor is NULL ? skipping.");
				continue;
			}
//.........这里部分代码省略.........

/*
 * master_create_worker_shards creates empty shards for the given table based
 * on the specified number of initial shards. The function first gets a list of
 * candidate nodes and issues DDL commands on the nodes to create empty shard
 * placements on those nodes. The function then updates metadata on the master
 * node to make this shard (and its placements) visible. Note that the function
 * assumes the table is hash partitioned and calculates the min/max hash token
 * ranges for each shard, giving them an equal split of the hash space.
 */
Datum
master_create_worker_shards(PG_FUNCTION_ARGS)
{
	text *tableNameText = PG_GETARG_TEXT_P(0);
	int32 shardCount = PG_GETARG_INT32(1);
	int32 replicationFactor = PG_GETARG_INT32(2);

	Oid distributedTableId = ResolveRelationId(tableNameText);
	char relationKind = get_rel_relkind(distributedTableId);
	char *tableName = text_to_cstring(tableNameText);
	char shardStorageType = '\0';
	int32 shardIndex = 0;
	List *workerNodeList = NIL;
	List *ddlCommandList = NIL;
	int32 workerNodeCount = 0;
	uint32 placementAttemptCount = 0;
	uint32 hashTokenIncrement = 0;
	List *existingShardList = NIL;

	/* make sure table is hash partitioned */
	CheckHashPartitionedTable(distributedTableId);

	/* validate that shards haven't already been created for this table */
	existingShardList = LoadShardIntervalList(distributedTableId);
	if (existingShardList != NIL)
	{
		ereport(ERROR, (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
						errmsg("table \"%s\" has already had shards created for it",
							   tableName)));
	}

	/* make sure that at least one shard is specified */
	if (shardCount <= 0)
	{
		ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
						errmsg("shardCount must be positive")));
	}

	/* make sure that at least one replica is specified */
	if (replicationFactor <= 0)
	{
		ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
						errmsg("replicationFactor must be positive")));
	}

	/* calculate the split of the hash space */
	hashTokenIncrement = UINT_MAX / shardCount;

	/* load and sort the worker node list for deterministic placement */
	workerNodeList = ParseWorkerNodeFile(WORKER_LIST_FILENAME);
	workerNodeList = SortList(workerNodeList, CompareWorkerNodes);

	/* make sure we don't process cancel signals until all shards are created */
	HOLD_INTERRUPTS();

	/* retrieve the DDL commands for the table */
	ddlCommandList = TableDDLCommandList(distributedTableId);

	workerNodeCount = list_length(workerNodeList);
	if (replicationFactor > workerNodeCount)
	{
		ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
						errmsg("replicationFactor (%d) exceeds number of worker nodes "
							   "(%d)", replicationFactor, workerNodeCount),
						errhint("Add more worker nodes or try again with a lower "
								"replication factor.")));
	}

	/* if we have enough nodes, add an extra placement attempt for backup */
	placementAttemptCount = (uint32) replicationFactor;
	if (workerNodeCount > replicationFactor)
	{
		placementAttemptCount++;
	}

	/* set shard storage type according to relation type */
	if (relationKind == RELKIND_FOREIGN_TABLE)
	{
		shardStorageType = SHARD_STORAGE_FOREIGN;
	}
	else
	{
		shardStorageType = SHARD_STORAGE_TABLE;
	}

	for (shardIndex = 0; shardIndex < shardCount; shardIndex++)
	{
		uint64 shardId = NextSequenceId(SHARD_ID_SEQUENCE_NAME);
		int32 placementCount = 0;
		uint32 placementIndex = 0;
		uint32 roundRobinNodeIndex = shardIndex % workerNodeCount;
//.........这里部分代码省略.........

/*
 * AutoVacMain
 */
NON_EXEC_STATIC void
AutoVacMain(int argc, char *argv[])
{
    ListCell   *cell;
    List	   *dblist;
    autovac_dbase *db;
    TransactionId xidForceLimit;
    bool		for_xid_wrap;
    sigjmp_buf	local_sigjmp_buf;

    /* we are a postmaster subprocess now */
    IsUnderPostmaster = true;
    am_autovacuum = true;

    /* MPP-4990: Autovacuum always runs as utility-mode */
    Gp_role = GP_ROLE_UTILITY;

    /* reset MyProcPid */
    MyProcPid = getpid();

    /* record Start Time for logging */
    MyStartTime = time(NULL);

    /* Identify myself via ps */
    init_ps_display("autovacuum process", "", "", "");

    SetProcessingMode(InitProcessing);

    /*
     * If possible, make this process a group leader, so that the postmaster
     * can signal any child processes too.  (autovacuum probably never has
     * any child processes, but for consistency we make all postmaster
     * child processes do this.)
     */
#ifdef HAVE_SETSID
    if (setsid() < 0)
        elog(FATAL, "setsid() failed: %m");
#endif

    /*
     * Set up signal handlers.	We operate on databases much like a regular
     * backend, so we use the same signal handling.  See equivalent code in
     * tcop/postgres.c.
     *
     * Currently, we don't pay attention to postgresql.conf changes that
     * happen during a single daemon iteration, so we can ignore SIGHUP.
     */
    pqsignal(SIGHUP, SIG_IGN);

    /*
     * SIGINT is used to signal cancelling the current table's vacuum; SIGTERM
     * means abort and exit cleanly, and SIGQUIT means abandon ship.
     */
    pqsignal(SIGINT, StatementCancelHandler);
    pqsignal(SIGTERM, die);
    pqsignal(SIGQUIT, quickdie);
    pqsignal(SIGALRM, handle_sig_alarm);

    pqsignal(SIGPIPE, SIG_IGN);
    pqsignal(SIGUSR1, procsignal_sigusr1_handler);
    /* We don't listen for async notifies */
    pqsignal(SIGUSR2, SIG_IGN);
    pqsignal(SIGFPE, FloatExceptionHandler);
    pqsignal(SIGCHLD, SIG_DFL);

    /* Early initialization */
    BaseInit();

    /*
     * Create a per-backend PGPROC struct in shared memory, except in the
     * EXEC_BACKEND case where this was done in SubPostmasterMain. We must do
     * this before we can use LWLocks (and in the EXEC_BACKEND case we already
     * had to do some stuff with LWLocks).
     */
#ifndef EXEC_BACKEND
    InitProcess();
#endif

    /*
     * If an exception is encountered, processing resumes here.
     *
     * See notes in postgres.c about the design of this coding.
     */
    if (sigsetjmp(local_sigjmp_buf, 1) != 0)
    {
        /* Prevents interrupts while cleaning up */
        HOLD_INTERRUPTS();

        /* Report the error to the server log */
        EmitErrorReport();

        /*
         * We can now go away.	Note that because we called InitProcess, a
         * callback was registered to do ProcKill, which will clean up
         * necessary state.
         */
        proc_exit(0);
//.........这里部分代码省略.........

/*
 * Workfile-manager specific function to clean up before releasing a
 * workfile set from the cache.
 *
 */
static void
workfile_mgr_cleanup_set(const void *resource)
{
	workfile_set *work_set = (workfile_set *) resource;

	/*
	 *  We have to make this callback function return cleanly ALL the
	 *  time. It shouldn't throw an exception.
	 *  We must try to clean up as much as we can in the callback, and
	 *  then never be called again.
	 *  This means holding interrupts, catching and handling all exceptions.
	 */

	if (work_set->on_disk)
	{
		ereport(gp_workfile_caching_loglevel,
				(errmsg("workfile mgr cleanup deleting set: key=0x%0xd, size=" INT64_FORMAT
				" in_progress_size=" INT64_FORMAT " path=%s",
				work_set->key,
				work_set->size,
				work_set->in_progress_size,
				work_set->path),
				errprintstack(true)));

		Assert(NULL == work_set->set_plan);

		PG_TRY();
		{

#ifdef FAULT_INJECTOR
			FaultInjector_InjectFaultIfSet(
				WorkfileCleanupSet,
				DDLNotSpecified,
				"", /* databaseName */
				"" /* tableName */
				);
#endif

			/* Prevent interrupts while cleaning up */
			HOLD_INTERRUPTS();

			workfile_mgr_delete_set_directory(work_set->path);

			/* Now we can allow interrupts again */
			RESUME_INTERRUPTS();

		}
		PG_CATCH();
		{
			elog(LOG, "Cleaning up workfile set directory path=%s failed. Proceeding",
					work_set->path);

			/* We're not re-throwing the error. Otherwise we'll end up having
			 * to clean up again, probably failing again.
			 */
		}
		PG_END_TRY();

		/*
		 * The most accurate size of a workset is recorded in work_set->in_progress_size.
		 * work_set->size is only updated when we close a file, so it lags behind
		 */

		Assert(work_set->in_progress_size >= work_set->size);
		int64 size_to_delete = work_set->in_progress_size;

		elog(gp_workfile_caching_loglevel, "Subtracting " INT64_FORMAT " from workfile diskspace", size_to_delete);

		/*
		 * When subtracting the size of this workset from our accounting,
		 * only update the per-query counter if we created the workset.
		 * In that case, the state is ACQUIRED, otherwise is CACHED or DELETED
		 */
		CacheEntry *cacheEntry = CACHE_ENTRY_HEADER(resource);
		bool update_query_space = (cacheEntry->state == CACHE_ENTRY_ACQUIRED);

		WorkfileDiskspace_Commit(0, size_to_delete, update_query_space);
	}
	else
	{
		/* Non-physical workfile set, we need to free up the plan memory */
		if (NULL != work_set->set_plan->serialized_plan)
		{
			pfree(work_set->set_plan->serialized_plan);
		}

		if (NULL != work_set->set_plan)
		{
			pfree(work_set->set_plan);
		}
	}
}

/*
 * LWLockConditionalAcquire - acquire a lightweight lock in the specified mode
 *
 * If the lock is not available, return FALSE with no side-effects.
 *
 * If successful, cancel/die interrupts are held off until lock release.
 */
bool
LWLockConditionalAcquire(LWLockId lockid, LWLockMode mode)
{
	volatile LWLock *lock = &(LWLockArray[lockid].lock);
#if LWLOCK_LOCK_PARTS > 1
	volatile LWLockPart *part = LWLOCK_PART(lock, lockid, MyBackendId);
#endif
	bool		mustwait;

	PRINT_LWDEBUG("LWLockConditionalAcquire", lockid, lock);

	/* Ensure we will have room to remember the lock */
	if (num_held_lwlocks >= MAX_SIMUL_LWLOCKS)
		elog(ERROR, "too many LWLocks taken");

	/*
	 * Lock out cancel/die interrupts until we exit the code section protected
	 * by the LWLock.  This ensures that interrupts will not interfere with
	 * manipulations of data structures in shared memory.
	 */
	HOLD_INTERRUPTS();

	if (mode == LW_SHARED)
	{
#ifdef LWLOCK_PART_SHARED_OPS_ATOMIC
		/* Increment shared counter partition. If there's no contention,
		 * this is sufficient to take the lock
		 */
		LWLOCK_PART_SHARED_POSTINC_ATOMIC(lock, lockid, part, MyBackendId);
		LWLOCK_PART_SHARED_FENCE();

		/* A concurrent exclusive locking attempt does the following
		 * three steps
		 *   1) Acquire mutex
		 *   2) Check shared counter partitions for readers.
		 *   3a) If found add proc to wait queue, block, restart at (1)
		 *   3b) If not found, set exclusive flag, continue with (4)
		 *   4) Enter protected section
		 * The fence after the atomic add above ensures that no further
		 * such attempt can proceed to (3b) or beyond. There may be
		 * pre-existing exclusive locking attempts at step (3b) or beyond,
		 * but we can recognize those by either the mutex being taken, or
		 * the exclusive flag being set. Conversely, if we see neither, we
		 * may proceed and enter the protected section.
		 *
		 * FIXME: This doesn't work if slock_t is a struct or doesn't
		 * use 0 for state "unlocked".
		 */

		if ((lock->mutex == 0) && (lock->exclusive == 0))
			goto lock_acquired;

		/* At this point, we don't know if the concurrent exclusive locker
		 * has proceeded to (3b) or blocked. We must take the mutex and
		 * re-check
		 */
#endif /* LWLOCK_PART_SHARED_OPS_ATOMIC */

		/* Acquire mutex.  Time spent holding mutex should be short! */
		SpinLockAcquire(&lock->mutex);

		if (lock->exclusive == 0)
		{
#ifdef LWLOCK_PART_SHARED_OPS_ATOMIC
			/* Already incremented the shared counter partition above */
#else
			lock->shared++;
#endif
			mustwait = false;
		}
		else
		{
#ifdef LWLOCK_PART_SHARED_OPS_ATOMIC
			/* Must undo shared counter partition increment. Note that
			 * we *need* to do that while holding the mutex. Otherwise,
			 * the exclusive lock could be released and attempted to be
			 * re-acquired before we undo the increment. That attempt
			 * would then block, even though there'd be no lock holder
			 * left
			 */
			LWLOCK_PART_SHARED_POSTDEC_ATOMIC(lock, lockid, part, MyBackendId);
#endif
			mustwait = true;
		}
	}
	else
	{
		/* Step (1). Acquire mutex. Time spent holding mutex should be
		 *                          short!
		 */
		SpinLockAcquire(&lock->mutex);

		if (lock->exclusive == 0)
//.........这里部分代码省略.........

/*
 * Main entry point for bgwriter process
 *
 * This is invoked from BootstrapMain, which has already created the basic
 * execution environment, but not enabled signals yet.
 */
void
BackgroundWriterMain(void)
{
	sigjmp_buf	local_sigjmp_buf;
	MemoryContext bgwriter_context;

	BgWriterShmem->bgwriter_pid = MyProcPid;
	am_bg_writer = true;

	/*
	 * If possible, make this process a group leader, so that the postmaster
	 * can signal any child processes too.	(bgwriter probably never has any
	 * child processes, but for consistency we make all postmaster child
	 * processes do this.)
	 */
#ifdef HAVE_SETSID
	if (setsid() < 0)
		elog(FATAL, "setsid() failed: %m");
#endif

	/*
	 * Properly accept or ignore signals the postmaster might send us
	 *
	 * Note: we deliberately ignore SIGTERM, because during a standard Unix
	 * system shutdown cycle, init will SIGTERM all processes at once.	We
	 * want to wait for the backends to exit, whereupon the postmaster will
	 * tell us it's okay to shut down (via SIGUSR2).
	 *
	 * SIGUSR1 is presently unused; keep it spare in case someday we want this
	 * process to participate in sinval messaging.
	 */
	pqsignal(SIGHUP, BgSigHupHandler);	/* set flag to read config file */
	pqsignal(SIGINT, ReqCheckpointHandler);		/* request checkpoint */
	pqsignal(SIGTERM, SIG_IGN); /* ignore SIGTERM */
	pqsignal(SIGQUIT, bg_quickdie);		/* hard crash time */
	pqsignal(SIGALRM, SIG_IGN);
	pqsignal(SIGPIPE, SIG_IGN);
	pqsignal(SIGUSR1, SIG_IGN); /* reserve for sinval */
	pqsignal(SIGUSR2, ReqShutdownHandler);		/* request shutdown */

	/*
	 * Reset some signals that are accepted by postmaster but not here
	 */
	pqsignal(SIGCHLD, SIG_DFL);
	pqsignal(SIGTTIN, SIG_DFL);
	pqsignal(SIGTTOU, SIG_DFL);
	pqsignal(SIGCONT, SIG_DFL);
	pqsignal(SIGWINCH, SIG_DFL);

	/* We allow SIGQUIT (quickdie) at all times */
#ifdef HAVE_SIGPROCMASK
	sigdelset(&BlockSig, SIGQUIT);
#else
	BlockSig &= ~(sigmask(SIGQUIT));
#endif

	/*
	 * Initialize so that first time-driven event happens at the correct time.
	 */
	last_checkpoint_time = last_xlog_switch_time = time(NULL);

	/*
	 * Create a resource owner to keep track of our resources (currently only
	 * buffer pins).
	 */
	CurrentResourceOwner = ResourceOwnerCreate(NULL, "Background Writer");

	/*
	 * Create a memory context that we will do all our work in.  We do this so
	 * that we can reset the context during error recovery and thereby avoid
	 * possible memory leaks.  Formerly this code just ran in
	 * TopMemoryContext, but resetting that would be a really bad idea.
	 */
	bgwriter_context = AllocSetContextCreate(TopMemoryContext,
											 "Background Writer",
											 ALLOCSET_DEFAULT_MINSIZE,
											 ALLOCSET_DEFAULT_INITSIZE,
											 ALLOCSET_DEFAULT_MAXSIZE);
	MemoryContextSwitchTo(bgwriter_context);

	/*
	 * If an exception is encountered, processing resumes here.
	 *
	 * See notes in postgres.c about the design of this coding.
	 */
	if (sigsetjmp(local_sigjmp_buf, 1) != 0)
	{
		/* Since not using PG_TRY, must reset error stack by hand */
		error_context_stack = NULL;

		/* Prevent interrupts while cleaning up */
		HOLD_INTERRUPTS();

		/* Report the error to the server log */
//.........这里部分代码省略.........

/*
 * Main entry point for walwriter process
 *
 * This is invoked from BootstrapMain, which has already created the basic
 * execution environment, but not enabled signals yet.
 */
void
WalWriterMain(void)
{
	sigjmp_buf	local_sigjmp_buf;
	MemoryContext walwriter_context;

	/*
	 * If possible, make this process a group leader, so that the postmaster
	 * can signal any child processes too.	(walwriter probably never has any
	 * child processes, but for consistency we make all postmaster child
	 * processes do this.)
	 */
#ifdef HAVE_SETSID
	if (setsid() < 0)
		elog(FATAL, "setsid() failed: %m");
#endif

	/*
	 * Properly accept or ignore signals the postmaster might send us
	 *
	 * We have no particular use for SIGINT at the moment, but seems
	 * reasonable to treat like SIGTERM.
	 */
	pqsignal(SIGHUP, WalSigHupHandler); /* set flag to read config file */
	pqsignal(SIGINT, WalShutdownHandler);		/* request shutdown */
	pqsignal(SIGTERM, WalShutdownHandler);		/* request shutdown */
	pqsignal(SIGQUIT, wal_quickdie);	/* hard crash time */
	pqsignal(SIGALRM, SIG_IGN);
	pqsignal(SIGPIPE, SIG_IGN);
	pqsignal(SIGUSR1, SIG_IGN); /* reserve for ProcSignal */
	pqsignal(SIGUSR2, SIG_IGN); /* not used */

	/*
	 * Reset some signals that are accepted by postmaster but not here
	 */
	pqsignal(SIGCHLD, SIG_DFL);
	pqsignal(SIGTTIN, SIG_DFL);
	pqsignal(SIGTTOU, SIG_DFL);
	pqsignal(SIGCONT, SIG_DFL);
	pqsignal(SIGWINCH, SIG_DFL);

	/* We allow SIGQUIT (quickdie) at all times */
	sigdelset(&BlockSig, SIGQUIT);

	/*
	 * Create a resource owner to keep track of our resources (not clear that
	 * we need this, but may as well have one).
	 */
	CurrentResourceOwner = ResourceOwnerCreate(NULL, "Wal Writer");

	/*
	 * Create a memory context that we will do all our work in.  We do this so
	 * that we can reset the context during error recovery and thereby avoid
	 * possible memory leaks.  Formerly this code just ran in
	 * TopMemoryContext, but resetting that would be a really bad idea.
	 */
	walwriter_context = AllocSetContextCreate(TopMemoryContext,
											  "Wal Writer",
											  ALLOCSET_DEFAULT_MINSIZE,
											  ALLOCSET_DEFAULT_INITSIZE,
											  ALLOCSET_DEFAULT_MAXSIZE);
	MemoryContextSwitchTo(walwriter_context);

	/*
	 * If an exception is encountered, processing resumes here.
	 *
	 * This code is heavily based on bgwriter.c, q.v.
	 */
	if (sigsetjmp(local_sigjmp_buf, 1) != 0)
	{
		/* Since not using PG_TRY, must reset error stack by hand */
		error_context_stack = NULL;

		/* Prevent interrupts while cleaning up */
		HOLD_INTERRUPTS();

		/* Report the error to the server log */
		EmitErrorReport();

		/*
		 * These operations are really just a minimal subset of
		 * AbortTransaction().	We don't have very many resources to worry
		 * about in walwriter, but we do have LWLocks, and perhaps buffers?
		 */
		LWLockReleaseAll();
		AbortBufferIO();
		UnlockBuffers();
		/* buffer pins are released here: */
		ResourceOwnerRelease(CurrentResourceOwner,
							 RESOURCE_RELEASE_BEFORE_LOCKS,
							 false, true);
		/* we needn't bother with the other ResourceOwnerRelease phases */
		AtEOXact_Buffers(false);
		AtEOXact_Files();
//.........这里部分代码省略.........