Adding upstream version 14.5.upstream/14.5upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1354 insertions, 0 deletions

diff --git a/src/backend/postmaster/checkpointer.c b/src/backend/postmaster/checkpointer.c
new file mode 100644
index 0000000..8699675
--- /dev/null
+++ b/src/backend/postmaster/checkpointer.c
@@ -0,0 +1,1354 @@
+/*-------------------------------------------------------------------------
+ *
+ * checkpointer.c
+ *
+ * The checkpointer is new as of Postgres 9.2.  It handles all checkpoints.
+ * Checkpoints are automatically dispatched after a certain amount of time has
+ * elapsed since the last one, and it can be signaled to perform requested
+ * checkpoints as well.  (The GUC parameter that mandates a checkpoint every
+ * so many WAL segments is implemented by having backends signal when they
+ * fill WAL segments; the checkpointer itself doesn't watch for the
+ * condition.)
+ *
+ * The checkpointer is started by the postmaster as soon as the startup
+ * subprocess finishes, or as soon as recovery begins if we are doing archive
+ * recovery.  It remains alive until the postmaster commands it to terminate.
+ * Normal termination is by SIGUSR2, which instructs the checkpointer to
+ * execute a shutdown checkpoint and then exit(0).  (All backends must be
+ * stopped before SIGUSR2 is issued!)  Emergency termination is by SIGQUIT;
+ * like any backend, the checkpointer will simply abort and exit on SIGQUIT.
+ *
+ * If the checkpointer exits unexpectedly, the postmaster treats that the same
+ * as a backend crash: shared memory may be corrupted, so remaining backends
+ * should be killed by SIGQUIT and then a recovery cycle started.  (Even if
+ * shared memory isn't corrupted, we have lost information about which
+ * files need to be fsync'd for the next checkpoint, and so a system
+ * restart needs to be forced.)
+ *
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/postmaster/checkpointer.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include <sys/time.h>
+#include <time.h>
+
+#include "access/xlog.h"
+#include "access/xlog_internal.h"
+#include "libpq/pqsignal.h"
+#include "miscadmin.h"
+#include "pgstat.h"
+#include "postmaster/bgwriter.h"
+#include "postmaster/interrupt.h"
+#include "replication/syncrep.h"
+#include "storage/bufmgr.h"
+#include "storage/condition_variable.h"
+#include "storage/fd.h"
+#include "storage/ipc.h"
+#include "storage/lwlock.h"
+#include "storage/proc.h"
+#include "storage/procsignal.h"
+#include "storage/shmem.h"
+#include "storage/smgr.h"
+#include "storage/spin.h"
+#include "utils/guc.h"
+#include "utils/memutils.h"
+#include "utils/resowner.h"
+
+
+/*----------
+ * Shared memory area for communication between checkpointer and backends
+ *
+ * The ckpt counters allow backends to watch for completion of a checkpoint
+ * request they send.  Here's how it works:
+ *	* At start of a checkpoint, checkpointer reads (and clears) the request
+ *	  flags and increments ckpt_started, while holding ckpt_lck.
+ *	* On completion of a checkpoint, checkpointer sets ckpt_done to
+ *	  equal ckpt_started.
+ *	* On failure of a checkpoint, checkpointer increments ckpt_failed
+ *	  and sets ckpt_done to equal ckpt_started.
+ *
+ * The algorithm for backends is:
+ *	1. Record current values of ckpt_failed and ckpt_started, and
+ *	   set request flags, while holding ckpt_lck.
+ *	2. Send signal to request checkpoint.
+ *	3. Sleep until ckpt_started changes.  Now you know a checkpoint has
+ *	   begun since you started this algorithm (although *not* that it was
+ *	   specifically initiated by your signal), and that it is using your flags.
+ *	4. Record new value of ckpt_started.
+ *	5. Sleep until ckpt_done >= saved value of ckpt_started.  (Use modulo
+ *	   arithmetic here in case counters wrap around.)  Now you know a
+ *	   checkpoint has started and completed, but not whether it was
+ *	   successful.
+ *	6. If ckpt_failed is different from the originally saved value,
+ *	   assume request failed; otherwise it was definitely successful.
+ *
+ * ckpt_flags holds the OR of the checkpoint request flags sent by all
+ * requesting backends since the last checkpoint start.  The flags are
+ * chosen so that OR'ing is the correct way to combine multiple requests.
+ *
+ * num_backend_writes is used to count the number of buffer writes performed
+ * by user backend processes.  This counter should be wide enough that it
+ * can't overflow during a single processing cycle.  num_backend_fsync
+ * counts the subset of those writes that also had to do their own fsync,
+ * because the checkpointer failed to absorb their request.
+ *
+ * The requests array holds fsync requests sent by backends and not yet
+ * absorbed by the checkpointer.
+ *
+ * Unlike the checkpoint fields, num_backend_writes, num_backend_fsync, and
+ * the requests fields are protected by CheckpointerCommLock.
+ *----------
+ */
+typedef struct
+{
+	SyncRequestType type;		/* request type */
+	FileTag		ftag;			/* file identifier */
+} CheckpointerRequest;
+
+typedef struct
+{
+	pid_t		checkpointer_pid;	/* PID (0 if not started) */
+
+	slock_t		ckpt_lck;		/* protects all the ckpt_* fields */
+
+	int			ckpt_started;	/* advances when checkpoint starts */
+	int			ckpt_done;		/* advances when checkpoint done */
+	int			ckpt_failed;	/* advances when checkpoint fails */
+
+	int			ckpt_flags;		/* checkpoint flags, as defined in xlog.h */
+
+	ConditionVariable start_cv; /* signaled when ckpt_started advances */
+	ConditionVariable done_cv;	/* signaled when ckpt_done advances */
+
+	uint32		num_backend_writes; /* counts user backend buffer writes */
+	uint32		num_backend_fsync;	/* counts user backend fsync calls */
+
+	int			num_requests;	/* current # of requests */
+	int			max_requests;	/* allocated array size */
+	CheckpointerRequest requests[FLEXIBLE_ARRAY_MEMBER];
+} CheckpointerShmemStruct;
+
+static CheckpointerShmemStruct *CheckpointerShmem;
+
+/* interval for calling AbsorbSyncRequests in CheckpointWriteDelay */
+#define WRITES_PER_ABSORB		1000
+
+/*
+ * GUC parameters
+ */
+int			CheckPointTimeout = 300;
+int			CheckPointWarning = 30;
+double		CheckPointCompletionTarget = 0.9;
+
+/*
+ * Private state
+ */
+static bool ckpt_active = false;
+
+/* these values are valid when ckpt_active is true: */
+static pg_time_t ckpt_start_time;
+static XLogRecPtr ckpt_start_recptr;
+static double ckpt_cached_elapsed;
+
+static pg_time_t last_checkpoint_time;
+static pg_time_t last_xlog_switch_time;
+
+/* Prototypes for private functions */
+
+static void HandleCheckpointerInterrupts(void);
+static void CheckArchiveTimeout(void);
+static bool IsCheckpointOnSchedule(double progress);
+static bool ImmediateCheckpointRequested(void);
+static bool CompactCheckpointerRequestQueue(void);
+static void UpdateSharedMemoryConfig(void);
+
+/* Signal handlers */
+static void ReqCheckpointHandler(SIGNAL_ARGS);
+
+
+/*
+ * 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, SignalHandlerForConfigReload);
+	pqsignal(SIGINT, ReqCheckpointHandler); /* request checkpoint */
+	pqsignal(SIGTERM, SIG_IGN); /* ignore SIGTERM */
+	/* SIGQUIT handler was already set up by InitPostmasterChild */
+	pqsignal(SIGALRM, SIG_IGN);
+	pqsignal(SIGPIPE, SIG_IGN);
+	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
+	pqsignal(SIGUSR2, SignalHandlerForShutdownRequest);
+
+	/*
+	 * Reset some signals that are accepted by postmaster but not here
+	 */
+	pqsignal(SIGCHLD, SIG_DFL);
+
+	/*
+	 * 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 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.
+	 *
+	 * You might wonder why this isn't coded as an infinite loop around a
+	 * PG_TRY construct.  The reason is that this is the bottom of the
+	 * exception stack, and so with PG_TRY there would be no exception handler
+	 * in force at all during the CATCH part.  By leaving the outermost setjmp
+	 * always active, we have at least some chance of recovering from an error
+	 * during error recovery.  (If we get into an infinite loop thereby, it
+	 * will soon be stopped by overflow of elog.c's internal state stack.)
+	 *
+	 * Note that we use sigsetjmp(..., 1), so that the prevailing signal mask
+	 * (to wit, BlockSig) will be restored when longjmp'ing to here.  Thus,
+	 * signals other than SIGQUIT will be blocked until we complete error
+	 * recovery.  It might seem that this policy makes the HOLD_INTERRUPTS()
+	 * call redundant, but it is not since InterruptPending might be set
+	 * already.
+	 */
+	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();
+		ReleaseAuxProcessResources(false);
+		AtEOXact_Buffers(false);
+		AtEOXact_SMgr();
+		AtEOXact_Files(false);
+		AtEOXact_HashTables(false);
+
+		/* Warn any waiting backends that the checkpoint failed. */
+		if (ckpt_active)
+		{
+			SpinLockAcquire(&CheckpointerShmem->ckpt_lck);
+			CheckpointerShmem->ckpt_failed++;
+			CheckpointerShmem->ckpt_done = CheckpointerShmem->ckpt_started;
+			SpinLockRelease(&CheckpointerShmem->ckpt_lck);
+
+			ConditionVariableBroadcast(&CheckpointerShmem->done_cv);
+
+			ckpt_active = false;
+		}
+
+		/*
+		 * Now return to normal top-level context and clear ErrorContext for
+		 * next time.
+		 */
+		MemoryContextSwitchTo(checkpointer_context);
+		FlushErrorState();
+
+		/* Flush any leaked data in the top-level context */
+		MemoryContextResetAndDeleteChildren(checkpointer_context);
+
+		/* Now we can allow interrupts again */
+		RESUME_INTERRUPTS();
+
+		/*
+		 * Sleep at least 1 second after any error.  A write error is likely
+		 * to be repeated, and we don't want to be filling the error logs as
+		 * fast as we can.
+		 */
+		pg_usleep(1000000L);
+
+		/*
+		 * Close all open files after any error.  This is helpful on Windows,
+		 * where holding deleted files open causes various strange errors.
+		 * It's not clear we need it elsewhere, but shouldn't hurt.
+		 */
+		smgrcloseall();
+	}
+
+	/* We can now handle ereport(ERROR) */
+	PG_exception_stack = &local_sigjmp_buf;
+
+	/*
+	 * Unblock signals (they were blocked when the postmaster forked us)
+	 */
+	PG_SETMASK(&UnBlockSig);
+
+	/*
+	 * Ensure all shared memory values are set correctly for the config. Doing
+	 * this here ensures no race conditions from other concurrent updaters.
+	 */
+	UpdateSharedMemoryConfig();
+
+	/*
+	 * Advertise our latch that backends can use to wake us up while we're
+	 * sleeping.
+	 */
+	ProcGlobal->checkpointerLatch = &MyProc->procLatch;
+
+	/*
+	 * Loop forever
+	 */
+	for (;;)
+	{
+		bool		do_checkpoint = false;
+		int			flags = 0;
+		pg_time_t	now;
+		int			elapsed_secs;
+		int			cur_timeout;
+
+		/* Clear any already-pending wakeups */
+		ResetLatch(MyLatch);
+
+		/*
+		 * Process any requests or signals received recently.
+		 */
+		AbsorbSyncRequests();
+		HandleCheckpointerInterrupts();
+
+		/*
+		 * Detect a pending checkpoint request by checking whether the flags
+		 * word in shared memory is nonzero.  We shouldn't need to acquire the
+		 * ckpt_lck for this.
+		 */
+		if (((volatile CheckpointerShmemStruct *) CheckpointerShmem)->ckpt_flags)
+		{
+			do_checkpoint = true;
+			BgWriterStats.m_requested_checkpoints++;
+		}
+
+		/*
+		 * Force a checkpoint if too much time has elapsed since the last one.
+		 * Note that we count a timed checkpoint in stats only when this
+		 * occurs without an external request, but we set the CAUSE_TIME flag
+		 * bit even if there is also an external request.
+		 */
+		now = (pg_time_t) time(NULL);
+		elapsed_secs = now - last_checkpoint_time;
+		if (elapsed_secs >= CheckPointTimeout)
+		{
+			if (!do_checkpoint)
+				BgWriterStats.m_timed_checkpoints++;
+			do_checkpoint = true;
+			flags |= CHECKPOINT_CAUSE_TIME;
+		}
+
+		/*
+		 * Do a checkpoint if requested.
+		 */
+		if (do_checkpoint)
+		{
+			bool		ckpt_performed = false;
+			bool		do_restartpoint;
+
+			/*
+			 * Check if we should perform a checkpoint or a restartpoint. As a
+			 * side-effect, RecoveryInProgress() initializes TimeLineID if
+			 * it's not set yet.
+			 */
+			do_restartpoint = RecoveryInProgress();
+
+			/*
+			 * Atomically fetch the request flags to figure out what kind of a
+			 * checkpoint we should perform, and increase the started-counter
+			 * to acknowledge that we've started a new checkpoint.
+			 */
+			SpinLockAcquire(&CheckpointerShmem->ckpt_lck);
+			flags |= CheckpointerShmem->ckpt_flags;
+			CheckpointerShmem->ckpt_flags = 0;
+			CheckpointerShmem->ckpt_started++;
+			SpinLockRelease(&CheckpointerShmem->ckpt_lck);
+
+			ConditionVariableBroadcast(&CheckpointerShmem->start_cv);
+
+			/*
+			 * The end-of-recovery checkpoint is a real checkpoint that's
+			 * performed while we're still in recovery.
+			 */
+			if (flags & CHECKPOINT_END_OF_RECOVERY)
+				do_restartpoint = false;
+
+			/*
+			 * We will warn if (a) too soon since last checkpoint (whatever
+			 * caused it) and (b) somebody set the CHECKPOINT_CAUSE_XLOG flag
+			 * since the last checkpoint start.  Note in particular that this
+			 * implementation will not generate warnings caused by
+			 * CheckPointTimeout < CheckPointWarning.
+			 */
+			if (!do_restartpoint &&
+				(flags & CHECKPOINT_CAUSE_XLOG) &&
+				elapsed_secs < CheckPointWarning)
+				ereport(LOG,
+						(errmsg_plural("checkpoints are occurring too frequently (%d second apart)",
+									   "checkpoints are occurring too frequently (%d seconds apart)",
+									   elapsed_secs,
+									   elapsed_secs),
+						 errhint("Consider increasing the configuration parameter \"max_wal_size\".")));
+
+			/*
+			 * Initialize checkpointer-private variables used during
+			 * checkpoint.
+			 */
+			ckpt_active = true;
+			if (do_restartpoint)
+				ckpt_start_recptr = GetXLogReplayRecPtr(NULL);
+			else
+				ckpt_start_recptr = GetInsertRecPtr();
+			ckpt_start_time = now;
+			ckpt_cached_elapsed = 0;
+
+			/*
+			 * Do the checkpoint.
+			 */
+			if (!do_restartpoint)
+			{
+				CreateCheckPoint(flags);
+				ckpt_performed = true;
+			}
+			else
+				ckpt_performed = CreateRestartPoint(flags);
+
+			/*
+			 * After any checkpoint, close all smgr files.  This is so we
+			 * won't hang onto smgr references to deleted files indefinitely.
+			 */
+			smgrcloseall();
+
+			/*
+			 * Indicate checkpoint completion to any waiting backends.
+			 */
+			SpinLockAcquire(&CheckpointerShmem->ckpt_lck);
+			CheckpointerShmem->ckpt_done = CheckpointerShmem->ckpt_started;
+			SpinLockRelease(&CheckpointerShmem->ckpt_lck);
+
+			ConditionVariableBroadcast(&CheckpointerShmem->done_cv);
+
+			if (ckpt_performed)
+			{
+				/*
+				 * Note we record the checkpoint start time not end time as
+				 * last_checkpoint_time.  This is so that time-driven
+				 * checkpoints happen at a predictable spacing.
+				 */
+				last_checkpoint_time = now;
+			}
+			else
+			{
+				/*
+				 * We were not able to perform the restartpoint (checkpoints
+				 * throw an ERROR in case of error).  Most likely because we
+				 * have not received any new checkpoint WAL records since the
+				 * last restartpoint. Try again in 15 s.
+				 */
+				last_checkpoint_time = now - CheckPointTimeout + 15;
+			}
+
+			ckpt_active = false;
+
+			/* We may have received an interrupt during the checkpoint. */
+			HandleCheckpointerInterrupts();
+		}
+
+		/* Check for archive_timeout and switch xlog files if necessary. */
+		CheckArchiveTimeout();
+
+		/*
+		 * Send off activity statistics to the stats collector.  (The reason
+		 * why we re-use bgwriter-related code for this is that the bgwriter
+		 * and checkpointer used to be just one process.  It's probably not
+		 * worth the trouble to split the stats support into two independent
+		 * stats message types.)
+		 */
+		pgstat_send_bgwriter();
+
+		/* Send WAL statistics to the stats collector. */
+		pgstat_send_wal(true);
+
+		/*
+		 * If any checkpoint flags have been set, redo the loop to handle the
+		 * checkpoint without sleeping.
+		 */
+		if (((volatile CheckpointerShmemStruct *) CheckpointerShmem)->ckpt_flags)
+			continue;
+
+		/*
+		 * Sleep until we are signaled or it's time for another checkpoint or
+		 * xlog file switch.
+		 */
+		now = (pg_time_t) time(NULL);
+		elapsed_secs = now - last_checkpoint_time;
+		if (elapsed_secs >= CheckPointTimeout)
+			continue;			/* no sleep for us ... */
+		cur_timeout = CheckPointTimeout - elapsed_secs;
+		if (XLogArchiveTimeout > 0 && !RecoveryInProgress())
+		{
+			elapsed_secs = now - last_xlog_switch_time;
+			if (elapsed_secs >= XLogArchiveTimeout)
+				continue;		/* no sleep for us ... */
+			cur_timeout = Min(cur_timeout, XLogArchiveTimeout - elapsed_secs);
+		}
+
+		(void) WaitLatch(MyLatch,
+						 WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
+						 cur_timeout * 1000L /* convert to ms */ ,
+						 WAIT_EVENT_CHECKPOINTER_MAIN);
+	}
+}
+
+/*
+ * Process any new interrupts.
+ */
+static void
+HandleCheckpointerInterrupts(void)
+{
+	if (ProcSignalBarrierPending)
+		ProcessProcSignalBarrier();
+
+	if (ConfigReloadPending)
+	{
+		ConfigReloadPending = false;
+		ProcessConfigFile(PGC_SIGHUP);
+
+		/*
+		 * Checkpointer is the last process to shut down, so we ask it to hold
+		 * the keys for a range of other tasks required most of which have
+		 * nothing to do with checkpointing at all.
+		 *
+		 * For various reasons, some config values can change dynamically so
+		 * the primary copy of them is held in shared memory to make sure all
+		 * backends see the same value.  We make Checkpointer responsible for
+		 * updating the shared memory copy if the parameter setting changes
+		 * because of SIGHUP.
+		 */
+		UpdateSharedMemoryConfig();
+	}
+	if (ShutdownRequestPending)
+	{
+		/*
+		 * From here on, elog(ERROR) should end with exit(1), not send control
+		 * back to the sigsetjmp block above
+		 */
+		ExitOnAnyError = true;
+
+		/*
+		 * Close down the database.
+		 *
+		 * Since ShutdownXLOG() creates restartpoint or checkpoint, and
+		 * updates the statistics, increment the checkpoint request and send
+		 * the statistics to the stats collector.
+		 */
+		BgWriterStats.m_requested_checkpoints++;
+		ShutdownXLOG(0, 0);
+		pgstat_send_bgwriter();
+		pgstat_send_wal(true);
+
+		/* Normal exit from the checkpointer is here */
+		proc_exit(0);			/* done */
+	}
+}
+
+/*
+ * CheckArchiveTimeout -- check for archive_timeout and switch xlog files
+ *
+ * This will switch to a new WAL file and force an archive file write if
+ * meaningful activity is recorded in the current WAL file. This includes most
+ * writes, including just a single checkpoint record, but excludes WAL records
+ * that were inserted with the XLOG_MARK_UNIMPORTANT flag being set (like
+ * snapshots of running transactions).  Such records, depending on
+ * configuration, occur on regular intervals and don't contain important
+ * information.  This avoids generating archives with a few unimportant
+ * records.
+ */
+static void
+CheckArchiveTimeout(void)
+{
+	pg_time_t	now;
+	pg_time_t	last_time;
+	XLogRecPtr	last_switch_lsn;
+
+	if (XLogArchiveTimeout <= 0 || RecoveryInProgress())
+		return;
+
+	now = (pg_time_t) time(NULL);
+
+	/* First we do a quick check using possibly-stale local state. */
+	if ((int) (now - last_xlog_switch_time) < XLogArchiveTimeout)
+		return;
+
+	/*
+	 * Update local state ... note that last_xlog_switch_time is the last time
+	 * a switch was performed *or requested*.
+	 */
+	last_time = GetLastSegSwitchData(&last_switch_lsn);
+
+	last_xlog_switch_time = Max(last_xlog_switch_time, last_time);
+
+	/* Now we can do the real checks */
+	if ((int) (now - last_xlog_switch_time) >= XLogArchiveTimeout)
+	{
+		/*
+		 * Switch segment only when "important" WAL has been logged since the
+		 * last segment switch (last_switch_lsn points to end of segment
+		 * switch occurred in).
+		 */
+		if (GetLastImportantRecPtr() > last_switch_lsn)
+		{
+			XLogRecPtr	switchpoint;
+
+			/* mark switch as unimportant, avoids triggering checkpoints */
+			switchpoint = RequestXLogSwitch(true);
+
+			/*
+			 * If the returned pointer points exactly to a segment boundary,
+			 * assume nothing happened.
+			 */
+			if (XLogSegmentOffset(switchpoint, wal_segment_size) != 0)
+				elog(DEBUG1, "write-ahead log switch forced (archive_timeout=%d)",
+					 XLogArchiveTimeout);
+		}
+
+		/*
+		 * Update state in any case, so we don't retry constantly when the
+		 * system is idle.
+		 */
+		last_xlog_switch_time = now;
+	}
+}
+
+/*
+ * Returns true if an immediate checkpoint request is pending.  (Note that
+ * this does not check the *current* checkpoint's IMMEDIATE flag, but whether
+ * there is one pending behind it.)
+ */
+static bool
+ImmediateCheckpointRequested(void)
+{
+	volatile CheckpointerShmemStruct *cps = CheckpointerShmem;
+
+	/*
+	 * We don't need to acquire the ckpt_lck in this case because we're only
+	 * looking at a single flag bit.
+	 */
+	if (cps->ckpt_flags & CHECKPOINT_IMMEDIATE)
+		return true;
+	return false;
+}
+
+/*
+ * CheckpointWriteDelay -- control rate of checkpoint
+ *
+ * This function is called after each page write performed by BufferSync().
+ * It is responsible for throttling BufferSync()'s write rate to hit
+ * checkpoint_completion_target.
+ *
+ * The checkpoint request flags should be passed in; currently the only one
+ * examined is CHECKPOINT_IMMEDIATE, which disables delays between writes.
+ *
+ * 'progress' is an estimate of how much of the work has been done, as a
+ * fraction between 0.0 meaning none, and 1.0 meaning all done.
+ */
+void
+CheckpointWriteDelay(int flags, double progress)
+{
+	static int	absorb_counter = WRITES_PER_ABSORB;
+
+	/* Do nothing if checkpoint is being executed by non-checkpointer process */
+	if (!AmCheckpointerProcess())
+		return;
+
+	/*
+	 * Perform the usual duties and take a nap, unless we're behind schedule,
+	 * in which case we just try to catch up as quickly as possible.
+	 */
+	if (!(flags & CHECKPOINT_IMMEDIATE) &&
+		!ShutdownRequestPending &&
+		!ImmediateCheckpointRequested() &&
+		IsCheckpointOnSchedule(progress))
+	{
+		if (ConfigReloadPending)
+		{
+			ConfigReloadPending = false;
+			ProcessConfigFile(PGC_SIGHUP);
+			/* update shmem copies of config variables */
+			UpdateSharedMemoryConfig();
+		}
+
+		AbsorbSyncRequests();
+		absorb_counter = WRITES_PER_ABSORB;
+
+		CheckArchiveTimeout();
+
+		/*
+		 * Report interim activity statistics to the stats collector.
+		 */
+		pgstat_send_bgwriter();
+
+		/*
+		 * This sleep used to be connected to bgwriter_delay, typically 200ms.
+		 * That resulted in more frequent wakeups if not much work to do.
+		 * Checkpointer and bgwriter are no longer related so take the Big
+		 * Sleep.
+		 */
+		WaitLatch(MyLatch, WL_LATCH_SET | WL_EXIT_ON_PM_DEATH | WL_TIMEOUT,
+				  100,
+				  WAIT_EVENT_CHECKPOINT_WRITE_DELAY);
+		ResetLatch(MyLatch);
+	}
+	else if (--absorb_counter <= 0)
+	{
+		/*
+		 * Absorb pending fsync requests after each WRITES_PER_ABSORB write
+		 * operations even when we don't sleep, to prevent overflow of the
+		 * fsync request queue.
+		 */
+		AbsorbSyncRequests();
+		absorb_counter = WRITES_PER_ABSORB;
+	}
+
+	/* Check for barrier events. */
+	if (ProcSignalBarrierPending)
+		ProcessProcSignalBarrier();
+}
+
+/*
+ * IsCheckpointOnSchedule -- are we on schedule to finish this checkpoint
+ *		 (or restartpoint) in time?
+ *
+ * Compares the current progress against the time/segments elapsed since last
+ * checkpoint, and returns true if the progress we've made this far is greater
+ * than the elapsed time/segments.
+ */
+static bool
+IsCheckpointOnSchedule(double progress)
+{
+	XLogRecPtr	recptr;
+	struct timeval now;
+	double		elapsed_xlogs,
+				elapsed_time;
+
+	Assert(ckpt_active);
+
+	/* Scale progress according to checkpoint_completion_target. */
+	progress *= CheckPointCompletionTarget;
+
+	/*
+	 * Check against the cached value first. Only do the more expensive
+	 * calculations once we reach the target previously calculated. Since
+	 * neither time or WAL insert pointer moves backwards, a freshly
+	 * calculated value can only be greater than or equal to the cached value.
+	 */
+	if (progress < ckpt_cached_elapsed)
+		return false;
+
+	/*
+	 * Check progress against WAL segments written and CheckPointSegments.
+	 *
+	 * We compare the current WAL insert location against the location
+	 * computed before calling CreateCheckPoint. The code in XLogInsert that
+	 * actually triggers a checkpoint when CheckPointSegments is exceeded
+	 * compares against RedoRecPtr, so this is not completely accurate.
+	 * However, it's good enough for our purposes, we're only calculating an
+	 * estimate anyway.
+	 *
+	 * During recovery, we compare last replayed WAL record's location with
+	 * the location computed before calling CreateRestartPoint. That maintains
+	 * the same pacing as we have during checkpoints in normal operation, but
+	 * we might exceed max_wal_size by a fair amount. That's because there can
+	 * be a large gap between a checkpoint's redo-pointer and the checkpoint
+	 * record itself, and we only start the restartpoint after we've seen the
+	 * checkpoint record. (The gap is typically up to CheckPointSegments *
+	 * checkpoint_completion_target where checkpoint_completion_target is the
+	 * value that was in effect when the WAL was generated).
+	 */
+	if (RecoveryInProgress())
+		recptr = GetXLogReplayRecPtr(NULL);
+	else
+		recptr = GetInsertRecPtr();
+	elapsed_xlogs = (((double) (recptr - ckpt_start_recptr)) /
+					 wal_segment_size) / CheckPointSegments;
+
+	if (progress < elapsed_xlogs)
+	{
+		ckpt_cached_elapsed = elapsed_xlogs;
+		return false;
+	}
+
+	/*
+	 * Check progress against time elapsed and checkpoint_timeout.
+	 */
+	gettimeofday(&now, NULL);
+	elapsed_time = ((double) ((pg_time_t) now.tv_sec - ckpt_start_time) +
+					now.tv_usec / 1000000.0) / CheckPointTimeout;
+
+	if (progress < elapsed_time)
+	{
+		ckpt_cached_elapsed = elapsed_time;
+		return false;
+	}
+
+	/* It looks like we're on schedule. */
+	return true;
+}
+
+
+/* --------------------------------
+ *		signal handler routines
+ * --------------------------------
+ */
+
+/* SIGINT: set flag to run a normal checkpoint right away */
+static void
+ReqCheckpointHandler(SIGNAL_ARGS)
+{
+	int			save_errno = errno;
+
+	/*
+	 * The signaling process should have set ckpt_flags nonzero, so all we
+	 * need do is ensure that our main loop gets kicked out of any wait.
+	 */
+	SetLatch(MyLatch);
+
+	errno = save_errno;
+}
+
+
+/* --------------------------------
+ *		communication with backends
+ * --------------------------------
+ */
+
+/*
+ * CheckpointerShmemSize
+ *		Compute space needed for checkpointer-related shared memory
+ */
+Size
+CheckpointerShmemSize(void)
+{
+	Size		size;
+
+	/*
+	 * Currently, the size of the requests[] array is arbitrarily set equal to
+	 * NBuffers.  This may prove too large or small ...
+	 */
+	size = offsetof(CheckpointerShmemStruct, requests);
+	size = add_size(size, mul_size(NBuffers, sizeof(CheckpointerRequest)));
+
+	return size;
+}
+
+/*
+ * CheckpointerShmemInit
+ *		Allocate and initialize checkpointer-related shared memory
+ */
+void
+CheckpointerShmemInit(void)
+{
+	Size		size = CheckpointerShmemSize();
+	bool		found;
+
+	CheckpointerShmem = (CheckpointerShmemStruct *)
+		ShmemInitStruct("Checkpointer Data",
+						size,
+						&found);
+
+	if (!found)
+	{
+		/*
+		 * First time through, so initialize.  Note that we zero the whole
+		 * requests array; this is so that CompactCheckpointerRequestQueue can
+		 * assume that any pad bytes in the request structs are zeroes.
+		 */
+		MemSet(CheckpointerShmem, 0, size);
+		SpinLockInit(&CheckpointerShmem->ckpt_lck);
+		CheckpointerShmem->max_requests = NBuffers;
+		ConditionVariableInit(&CheckpointerShmem->start_cv);
+		ConditionVariableInit(&CheckpointerShmem->done_cv);
+	}
+}
+
+/*
+ * RequestCheckpoint
+ *		Called in backend processes to request a checkpoint
+ *
+ * flags is a bitwise OR of the following:
+ *	CHECKPOINT_IS_SHUTDOWN: checkpoint is for database shutdown.
+ *	CHECKPOINT_END_OF_RECOVERY: checkpoint is for end of WAL recovery.
+ *	CHECKPOINT_IMMEDIATE: finish the checkpoint ASAP,
+ *		ignoring checkpoint_completion_target parameter.
+ *	CHECKPOINT_FORCE: force a checkpoint even if no XLOG activity has occurred
+ *		since the last one (implied by CHECKPOINT_IS_SHUTDOWN or
+ *		CHECKPOINT_END_OF_RECOVERY).
+ *	CHECKPOINT_WAIT: wait for completion before returning (otherwise,
+ *		just signal checkpointer to do it, and return).
+ *	CHECKPOINT_CAUSE_XLOG: checkpoint is requested due to xlog filling.
+ *		(This affects logging, and in particular enables CheckPointWarning.)
+ */
+void
+RequestCheckpoint(int flags)
+{
+	int			ntries;
+	int			old_failed,
+				old_started;
+
+	/*
+	 * If in a standalone backend, just do it ourselves.
+	 */
+	if (!IsPostmasterEnvironment)
+	{
+		/*
+		 * There's no point in doing slow checkpoints in a standalone backend,
+		 * because there's no other backends the checkpoint could disrupt.
+		 */
+		CreateCheckPoint(flags | CHECKPOINT_IMMEDIATE);
+
+		/*
+		 * After any checkpoint, close all smgr files.  This is so we won't
+		 * hang onto smgr references to deleted files indefinitely.
+		 */
+		smgrcloseall();
+
+		return;
+	}
+
+	/*
+	 * Atomically set the request flags, and take a snapshot of the counters.
+	 * When we see ckpt_started > old_started, we know the flags we set here
+	 * have been seen by checkpointer.
+	 *
+	 * Note that we OR the flags with any existing flags, to avoid overriding
+	 * a "stronger" request by another backend.  The flag senses must be
+	 * chosen to make this work!
+	 */
+	SpinLockAcquire(&CheckpointerShmem->ckpt_lck);
+
+	old_failed = CheckpointerShmem->ckpt_failed;
+	old_started = CheckpointerShmem->ckpt_started;
+	CheckpointerShmem->ckpt_flags |= (flags | CHECKPOINT_REQUESTED);
+
+	SpinLockRelease(&CheckpointerShmem->ckpt_lck);
+
+	/*
+	 * Send signal to request checkpoint.  It's possible that the checkpointer
+	 * hasn't started yet, or is in process of restarting, so we will retry a
+	 * few times if needed.  (Actually, more than a few times, since on slow
+	 * or overloaded buildfarm machines, it's been observed that the
+	 * checkpointer can take several seconds to start.)  However, if not told
+	 * to wait for the checkpoint to occur, we consider failure to send the
+	 * signal to be nonfatal and merely LOG it.  The checkpointer should see
+	 * the request when it does start, with or without getting a signal.
+	 */
+#define MAX_SIGNAL_TRIES 600	/* max wait 60.0 sec */
+	for (ntries = 0;; ntries++)
+	{
+		if (CheckpointerShmem->checkpointer_pid == 0)
+		{
+			if (ntries >= MAX_SIGNAL_TRIES || !(flags & CHECKPOINT_WAIT))
+			{
+				elog((flags & CHECKPOINT_WAIT) ? ERROR : LOG,
+					 "could not signal for checkpoint: checkpointer is not running");
+				break;
+			}
+		}
+		else if (kill(CheckpointerShmem->checkpointer_pid, SIGINT) != 0)
+		{
+			if (ntries >= MAX_SIGNAL_TRIES || !(flags & CHECKPOINT_WAIT))
+			{
+				elog((flags & CHECKPOINT_WAIT) ? ERROR : LOG,
+					 "could not signal for checkpoint: %m");
+				break;
+			}
+		}
+		else
+			break;				/* signal sent successfully */
+
+		CHECK_FOR_INTERRUPTS();
+		pg_usleep(100000L);		/* wait 0.1 sec, then retry */
+	}
+
+	/*
+	 * If requested, wait for completion.  We detect completion according to
+	 * the algorithm given above.
+	 */
+	if (flags & CHECKPOINT_WAIT)
+	{
+		int			new_started,
+					new_failed;
+
+		/* Wait for a new checkpoint to start. */
+		ConditionVariablePrepareToSleep(&CheckpointerShmem->start_cv);
+		for (;;)
+		{
+			SpinLockAcquire(&CheckpointerShmem->ckpt_lck);
+			new_started = CheckpointerShmem->ckpt_started;
+			SpinLockRelease(&CheckpointerShmem->ckpt_lck);
+
+			if (new_started != old_started)
+				break;
+
+			ConditionVariableSleep(&CheckpointerShmem->start_cv,
+								   WAIT_EVENT_CHECKPOINT_START);
+		}
+		ConditionVariableCancelSleep();
+
+		/*
+		 * We are waiting for ckpt_done >= new_started, in a modulo sense.
+		 */
+		ConditionVariablePrepareToSleep(&CheckpointerShmem->done_cv);
+		for (;;)
+		{
+			int			new_done;
+
+			SpinLockAcquire(&CheckpointerShmem->ckpt_lck);
+			new_done = CheckpointerShmem->ckpt_done;
+			new_failed = CheckpointerShmem->ckpt_failed;
+			SpinLockRelease(&CheckpointerShmem->ckpt_lck);
+
+			if (new_done - new_started >= 0)
+				break;
+
+			ConditionVariableSleep(&CheckpointerShmem->done_cv,
+								   WAIT_EVENT_CHECKPOINT_DONE);
+		}
+		ConditionVariableCancelSleep();
+
+		if (new_failed != old_failed)
+			ereport(ERROR,
+					(errmsg("checkpoint request failed"),
+					 errhint("Consult recent messages in the server log for details.")));
+	}
+}
+
+/*
+ * ForwardSyncRequest
+ *		Forward a file-fsync request from a backend to the checkpointer
+ *
+ * Whenever a backend is compelled to write directly to a relation
+ * (which should be seldom, if the background writer is getting its job done),
+ * the backend calls this routine to pass over knowledge that the relation
+ * is dirty and must be fsync'd before next checkpoint.  We also use this
+ * opportunity to count such writes for statistical purposes.
+ *
+ * To avoid holding the lock for longer than necessary, we normally write
+ * to the requests[] queue without checking for duplicates.  The checkpointer
+ * will have to eliminate dups internally anyway.  However, if we discover
+ * that the queue is full, we make a pass over the entire queue to compact
+ * it.  This is somewhat expensive, but the alternative is for the backend
+ * to perform its own fsync, which is far more expensive in practice.  It
+ * is theoretically possible a backend fsync might still be necessary, if
+ * the queue is full and contains no duplicate entries.  In that case, we
+ * let the backend know by returning false.
+ */
+bool
+ForwardSyncRequest(const FileTag *ftag, SyncRequestType type)
+{
+	CheckpointerRequest *request;
+	bool		too_full;
+
+	if (!IsUnderPostmaster)
+		return false;			/* probably shouldn't even get here */
+
+	if (AmCheckpointerProcess())
+		elog(ERROR, "ForwardSyncRequest must not be called in checkpointer");
+
+	LWLockAcquire(CheckpointerCommLock, LW_EXCLUSIVE);
+
+	/* Count all backend writes regardless of if they fit in the queue */
+	if (!AmBackgroundWriterProcess())
+		CheckpointerShmem->num_backend_writes++;
+
+	/*
+	 * If the checkpointer isn't running or the request queue is full, the
+	 * backend will have to perform its own fsync request.  But before forcing
+	 * that to happen, we can try to compact the request queue.
+	 */
+	if (CheckpointerShmem->checkpointer_pid == 0 ||
+		(CheckpointerShmem->num_requests >= CheckpointerShmem->max_requests &&
+		 !CompactCheckpointerRequestQueue()))
+	{
+		/*
+		 * Count the subset of writes where backends have to do their own
+		 * fsync
+		 */
+		if (!AmBackgroundWriterProcess())
+			CheckpointerShmem->num_backend_fsync++;
+		LWLockRelease(CheckpointerCommLock);
+		return false;
+	}
+
+	/* OK, insert request */
+	request = &CheckpointerShmem->requests[CheckpointerShmem->num_requests++];
+	request->ftag = *ftag;
+	request->type = type;
+
+	/* If queue is more than half full, nudge the checkpointer to empty it */
+	too_full = (CheckpointerShmem->num_requests >=
+				CheckpointerShmem->max_requests / 2);
+
+	LWLockRelease(CheckpointerCommLock);
+
+	/* ... but not till after we release the lock */
+	if (too_full && ProcGlobal->checkpointerLatch)
+		SetLatch(ProcGlobal->checkpointerLatch);
+
+	return true;
+}
+
+/*
+ * CompactCheckpointerRequestQueue
+ *		Remove duplicates from the request queue to avoid backend fsyncs.
+ *		Returns "true" if any entries were removed.
+ *
+ * Although a full fsync request queue is not common, it can lead to severe
+ * performance problems when it does happen.  So far, this situation has
+ * only been observed to occur when the system is under heavy write load,
+ * and especially during the "sync" phase of a checkpoint.  Without this
+ * logic, each backend begins doing an fsync for every block written, which
+ * gets very expensive and can slow down the whole system.
+ *
+ * Trying to do this every time the queue is full could lose if there
+ * aren't any removable entries.  But that should be vanishingly rare in
+ * practice: there's one queue entry per shared buffer.
+ */
+static bool
+CompactCheckpointerRequestQueue(void)
+{
+	struct CheckpointerSlotMapping
+	{
+		CheckpointerRequest request;
+		int			slot;
+	};
+
+	int			n,
+				preserve_count;
+	int			num_skipped = 0;
+	HASHCTL		ctl;
+	HTAB	   *htab;
+	bool	   *skip_slot;
+
+	/* must hold CheckpointerCommLock in exclusive mode */
+	Assert(LWLockHeldByMe(CheckpointerCommLock));
+
+	/* Initialize skip_slot array */
+	skip_slot = palloc0(sizeof(bool) * CheckpointerShmem->num_requests);
+
+	/* Initialize temporary hash table */
+	ctl.keysize = sizeof(CheckpointerRequest);
+	ctl.entrysize = sizeof(struct CheckpointerSlotMapping);
+	ctl.hcxt = CurrentMemoryContext;
+
+	htab = hash_create("CompactCheckpointerRequestQueue",
+					   CheckpointerShmem->num_requests,
+					   &ctl,
+					   HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
+
+	/*
+	 * The basic idea here is that a request can be skipped if it's followed
+	 * by a later, identical request.  It might seem more sensible to work
+	 * backwards from the end of the queue and check whether a request is
+	 * *preceded* by an earlier, identical request, in the hopes of doing less
+	 * copying.  But that might change the semantics, if there's an
+	 * intervening SYNC_FORGET_REQUEST or SYNC_FILTER_REQUEST, so we do it
+	 * this way.  It would be possible to be even smarter if we made the code
+	 * below understand the specific semantics of such requests (it could blow
+	 * away preceding entries that would end up being canceled anyhow), but
+	 * it's not clear that the extra complexity would buy us anything.
+	 */
+	for (n = 0; n < CheckpointerShmem->num_requests; n++)
+	{
+		CheckpointerRequest *request;
+		struct CheckpointerSlotMapping *slotmap;
+		bool		found;
+
+		/*
+		 * We use the request struct directly as a hashtable key.  This
+		 * assumes that any padding bytes in the structs are consistently the
+		 * same, which should be okay because we zeroed them in
+		 * CheckpointerShmemInit.  Note also that RelFileNode had better
+		 * contain no pad bytes.
+		 */
+		request = &CheckpointerShmem->requests[n];
+		slotmap = hash_search(htab, request, HASH_ENTER, &found);
+		if (found)
+		{
+			/* Duplicate, so mark the previous occurrence as skippable */
+			skip_slot[slotmap->slot] = true;
+			num_skipped++;
+		}
+		/* Remember slot containing latest occurrence of this request value */
+		slotmap->slot = n;
+	}
+
+	/* Done with the hash table. */
+	hash_destroy(htab);
+
+	/* If no duplicates, we're out of luck. */
+	if (!num_skipped)
+	{
+		pfree(skip_slot);
+		return false;
+	}
+
+	/* We found some duplicates; remove them. */
+	preserve_count = 0;
+	for (n = 0; n < CheckpointerShmem->num_requests; n++)
+	{
+		if (skip_slot[n])
+			continue;
+		CheckpointerShmem->requests[preserve_count++] = CheckpointerShmem->requests[n];
+	}
+	ereport(DEBUG1,
+			(errmsg_internal("compacted fsync request queue from %d entries to %d entries",
+							 CheckpointerShmem->num_requests, preserve_count)));
+	CheckpointerShmem->num_requests = preserve_count;
+
+	/* Cleanup. */
+	pfree(skip_slot);
+	return true;
+}
+
+/*
+ * AbsorbSyncRequests
+ *		Retrieve queued sync requests and pass them to sync mechanism.
+ *
+ * This is exported because it must be called during CreateCheckPoint;
+ * we have to be sure we have accepted all pending requests just before
+ * we start fsync'ing.  Since CreateCheckPoint sometimes runs in
+ * non-checkpointer processes, do nothing if not checkpointer.
+ */
+void
+AbsorbSyncRequests(void)
+{
+	CheckpointerRequest *requests = NULL;
+	CheckpointerRequest *request;
+	int			n;
+
+	if (!AmCheckpointerProcess())
+		return;
+
+	LWLockAcquire(CheckpointerCommLock, LW_EXCLUSIVE);
+
+	/* Transfer stats counts into pending pgstats message */
+	BgWriterStats.m_buf_written_backend += CheckpointerShmem->num_backend_writes;
+	BgWriterStats.m_buf_fsync_backend += CheckpointerShmem->num_backend_fsync;
+
+	CheckpointerShmem->num_backend_writes = 0;
+	CheckpointerShmem->num_backend_fsync = 0;
+
+	/*
+	 * We try to avoid holding the lock for a long time by copying the request
+	 * array, and processing the requests after releasing the lock.
+	 *
+	 * Once we have cleared the requests from shared memory, we have to PANIC
+	 * if we then fail to absorb them (eg, because our hashtable runs out of
+	 * memory).  This is because the system cannot run safely if we are unable
+	 * to fsync what we have been told to fsync.  Fortunately, the hashtable
+	 * is so small that the problem is quite unlikely to arise in practice.
+	 */
+	n = CheckpointerShmem->num_requests;
+	if (n > 0)
+	{
+		requests = (CheckpointerRequest *) palloc(n * sizeof(CheckpointerRequest));
+		memcpy(requests, CheckpointerShmem->requests, n * sizeof(CheckpointerRequest));
+	}
+
+	START_CRIT_SECTION();
+
+	CheckpointerShmem->num_requests = 0;
+
+	LWLockRelease(CheckpointerCommLock);
+
+	for (request = requests; n > 0; request++, n--)
+		RememberSyncRequest(&request->ftag, request->type);
+
+	END_CRIT_SECTION();
+
+	if (requests)
+		pfree(requests);
+}
+
+/*
+ * Update any shared memory configurations based on config parameters
+ */
+static void
+UpdateSharedMemoryConfig(void)
+{
+	/* update global shmem state for sync rep */
+	SyncRepUpdateSyncStandbysDefined();
+
+	/*
+	 * If full_page_writes has been changed by SIGHUP, we update it in shared
+	 * memory and write an XLOG_FPW_CHANGE record.
+	 */
+	UpdateFullPageWrites();
+
+	elog(DEBUG2, "checkpointer updated shared memory configuration values");
+}
+
+/*
+ * FirstCallSinceLastCheckpoint allows a process to take an action once
+ * per checkpoint cycle by asynchronously checking for checkpoint completion.
+ */
+bool
+FirstCallSinceLastCheckpoint(void)
+{
+	static int	ckpt_done = 0;
+	int			new_done;
+	bool		FirstCall = false;
+
+	SpinLockAcquire(&CheckpointerShmem->ckpt_lck);
+	new_done = CheckpointerShmem->ckpt_done;
+	SpinLockRelease(&CheckpointerShmem->ckpt_lck);
+
+	if (new_done != ckpt_done)
+		FirstCall = true;
+
+	ckpt_done = new_done;
+
+	return FirstCall;
+}