Cross-check lists of built-in LWLock tranches.

lwlock.c, lwlock.h, and wait_event_names.txt each contain a list of
built-in LWLock tranches.  It is easy to miss one or the other when
adding or removing tranches, and discrepancies have adverse effects
(e.g., breaking JOINs between pg_stat_activity and pg_wait_events).
This commit moves the lists of built-in tranches in lwlock.{c,h} to
lwlocklist.h and adds a cross-check to the script that generates
lwlocknames.h.  If the lists do not match exactly, building will
fail.

Author: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/aHpOgwuFQfcFMZ/B%40ip-10-97-1-34.eu-west-3.compute.internal

src/backend/storage/lmgr/generate-lwlocknames.pl

@@ -27,18 +27,24 @@ print $h "/* there is deliberately not an #ifndef LWLOCKNAMES_H here */\n\n";
 
 
 #
-# First, record the predefined LWLocks listed in wait_event_names.txt.  We'll
+# First, record the predefined LWLocks and built-in tranches listed in
-# cross-check those with the ones in lwlocklist.h.
+# wait_event_names.txt.  We'll cross-check those with the ones in lwlocklist.h.
 #
+my @wait_event_tranches;
 my @wait_event_lwlocks;
 my $record_lwlocks = 0;
+my $in_tranches = 0;
 
 while (<$wait_event_names>)
 {
 	chomp;
 
 	# Check for end marker.
-	last if /^# END OF PREDEFINED LWLOCKS/;
+	if (/^# END OF PREDEFINED LWLOCKS/)
+	{
+		$in_tranches = 1;
+		next;
+	}
 
 	# Skip comments and empty lines.
 	next if /^#/;
@@ -54,13 +60,29 @@ while (<$wait_event_names>)
 	# Go to the next line if we are not yet recording LWLocks.
 	next if not $record_lwlocks;
 
+	# Stop recording if we reach another section.
+	last if /^Section:/;
+
 	# Record the LWLock.
 	(my $waiteventname, my $waitevendocsentence) = split(/\t/, $_);
-	push(@wait_event_lwlocks, $waiteventname);
+
+	if ($in_tranches)
+	{
+		push(@wait_event_tranches, $waiteventname);
+	}
+	else
+	{
+		push(@wait_event_lwlocks, $waiteventname);
+	}
 }
 
+#
+# While gathering the list of predefined LWLocks, cross-check the lists in
+# lwlocklist.h with the wait events we just recorded.
+#
 my $in_comment = 0;
-my $i = 0;
+my $lwlock_count = 0;
+my $tranche_count = 0;
 while (<$lwlocklist>)
 {
 	chomp;
@@ -81,38 +103,72 @@ while (<$lwlocklist>)
 		next;
 	}
 
-	die "unable to parse lwlocklist.h line \"$_\""
+	#
-	  unless /^PG_LWLOCK\((\d+),\s+(\w+)\)$/;
+	# Gather list of predefined LWLocks and cross-check with the wait events.
+	#
+	if (/^PG_LWLOCK\((\d+),\s+(\w+)\)$/)
+	{
+		my ($lockidx, $lockname) = ($1, $2);
 
-	(my $lockidx, my $lockname) = ($1, $2);
+		die "lwlocklist.h not in order" if $lockidx < $lastlockidx;
+		die "lwlocklist.h has duplicates" if $lockidx == $lastlockidx;
 
-	die "lwlocklist.h not in order" if $lockidx < $lastlockidx;
+		die "$lockname defined in lwlocklist.h but missing from "
-	die "lwlocklist.h has duplicates" if $lockidx == $lastlockidx;
+		  . "wait_event_names.txt"
+		  if $lwlock_count >= scalar @wait_event_lwlocks;
+		die "lists of predefined LWLocks do not match (first mismatch at "
+		  . "$wait_event_lwlocks[$lwlock_count] in wait_event_names.txt and "
+		  . "$lockname in lwlocklist.h)"
+		  if $wait_event_lwlocks[$lwlock_count] ne $lockname;
 
-	die "$lockname defined in lwlocklist.h but missing from "
+		$lwlock_count++;
-	  . "wait_event_names.txt"
-	  if $i >= scalar @wait_event_lwlocks;
-	die "lists of predefined LWLocks do not match (first mismatch at "
-	  . "$wait_event_lwlocks[$i] in wait_event_names.txt and $lockname in "
-	  . "lwlocklist.h)"
-	  if $wait_event_lwlocks[$i] ne $lockname;
-	$i++;
 
-	while ($lastlockidx < $lockidx - 1)
+		while ($lastlockidx < $lockidx - 1)
+		{
+			++$lastlockidx;
+		}
+		$lastlockidx = $lockidx;
+
+		# Add a "Lock" suffix to each lock name, as the C code depends on that.
+		printf $h "#define %-32s (&MainLWLockArray[$lockidx].lock)\n",
+		  $lockname . "Lock";
+
+		next;
+	}
+
+	#
+	# Cross-check the built-in LWLock tranches with the wait events.
+	#
+	if (/^PG_LWLOCKTRANCHE\((\w+),\s+(\w+)\)$/)
 	{
-		++$lastlockidx;
+		my ($tranche_id, $tranche_name) = ($1, $2);
+
+		die "$tranche_name defined in lwlocklist.h but missing from "
+		  . "wait_event_names.txt"
+		  if $tranche_count >= scalar @wait_event_tranches;
+		die
+		  "lists of built-in LWLock tranches do not match (first mismatch at "
+		  . "$wait_event_tranches[$tranche_count] in wait_event_names.txt and "
+		  . "$tranche_name in lwlocklist.h)"
+		  if $wait_event_tranches[$tranche_count] ne $tranche_name;
+
+		$tranche_count++;
+
+		next;
 	}
-	$lastlockidx = $lockidx;
 
-	# Add a "Lock" suffix to each lock name, as the C code depends on that
+	die "unable to parse lwlocklist.h line \"$_\"";
-	printf $h "#define %-32s (&MainLWLockArray[$lockidx].lock)\n",
-	  $lockname . "Lock";
 }
 
 die
-  "$wait_event_lwlocks[$i] defined in wait_event_names.txt but missing from "
+  "$wait_event_lwlocks[$lwlock_count] defined in wait_event_names.txt but "
-  . "lwlocklist.h"
+  . " missing from lwlocklist.h"
-  if $i < scalar @wait_event_lwlocks;
+  if $lwlock_count < scalar @wait_event_lwlocks;
+
+die
+  "$wait_event_tranches[$tranche_count] defined in wait_event_names.txt but "
+  . "missing from lwlocklist.h"
+  if $tranche_count < scalar @wait_event_tranches;
 
 print $h "\n";
 printf $h "#define NUM_INDIVIDUAL_LWLOCKS		%s\n", $lastlockidx + 1;

src/backend/storage/lmgr/lwlock.c

@@ -122,9 +122,8 @@ StaticAssertDecl((LW_VAL_EXCLUSIVE & LW_FLAG_MASK) == 0,
  * own tranche.  We absorb the names of these tranches from there into
  * BuiltinTrancheNames here.
  *
- * 2. There are some predefined tranches for built-in groups of locks.
+ * 2. There are some predefined tranches for built-in groups of locks defined
- * These are listed in enum BuiltinTrancheIds in lwlock.h, and their names
+ * in lwlocklist.h.  We absorb the names of these tranches, too.
- * appear in BuiltinTrancheNames[] below.
  *
  * 3. Extensions can create new tranches, via either RequestNamedLWLockTranche
  * or LWLockRegisterTranche.  The names of these that are known in the current
@@ -135,49 +134,10 @@ StaticAssertDecl((LW_VAL_EXCLUSIVE & LW_FLAG_MASK) == 0,
  */
 static const char *const BuiltinTrancheNames[] = {
 #define PG_LWLOCK(id, lockname) [id] = CppAsString(lockname),
+#define PG_LWLOCKTRANCHE(id, lockname) [LWTRANCHE_##id] = CppAsString(lockname),
 #include "storage/lwlocklist.h"
 #undef PG_LWLOCK
-	[LWTRANCHE_XACT_BUFFER] = "XactBuffer",
+#undef PG_LWLOCKTRANCHE
-	[LWTRANCHE_COMMITTS_BUFFER] = "CommitTsBuffer",
-	[LWTRANCHE_SUBTRANS_BUFFER] = "SubtransBuffer",
-	[LWTRANCHE_MULTIXACTOFFSET_BUFFER] = "MultiXactOffsetBuffer",
-	[LWTRANCHE_MULTIXACTMEMBER_BUFFER] = "MultiXactMemberBuffer",
-	[LWTRANCHE_NOTIFY_BUFFER] = "NotifyBuffer",
-	[LWTRANCHE_SERIAL_BUFFER] = "SerialBuffer",
-	[LWTRANCHE_WAL_INSERT] = "WALInsert",
-	[LWTRANCHE_BUFFER_CONTENT] = "BufferContent",
-	[LWTRANCHE_REPLICATION_ORIGIN_STATE] = "ReplicationOriginState",
-	[LWTRANCHE_REPLICATION_SLOT_IO] = "ReplicationSlotIO",
-	[LWTRANCHE_LOCK_FASTPATH] = "LockFastPath",
-	[LWTRANCHE_BUFFER_MAPPING] = "BufferMapping",
-	[LWTRANCHE_LOCK_MANAGER] = "LockManager",
-	[LWTRANCHE_PREDICATE_LOCK_MANAGER] = "PredicateLockManager",
-	[LWTRANCHE_PARALLEL_HASH_JOIN] = "ParallelHashJoin",
-	[LWTRANCHE_PARALLEL_BTREE_SCAN] = "ParallelBtreeScan",
-	[LWTRANCHE_PARALLEL_QUERY_DSA] = "ParallelQueryDSA",
-	[LWTRANCHE_PER_SESSION_DSA] = "PerSessionDSA",
-	[LWTRANCHE_PER_SESSION_RECORD_TYPE] = "PerSessionRecordType",
-	[LWTRANCHE_PER_SESSION_RECORD_TYPMOD] = "PerSessionRecordTypmod",
-	[LWTRANCHE_SHARED_TUPLESTORE] = "SharedTupleStore",
-	[LWTRANCHE_SHARED_TIDBITMAP] = "SharedTidBitmap",
-	[LWTRANCHE_PARALLEL_APPEND] = "ParallelAppend",
-	[LWTRANCHE_PER_XACT_PREDICATE_LIST] = "PerXactPredicateList",
-	[LWTRANCHE_PGSTATS_DSA] = "PgStatsDSA",
-	[LWTRANCHE_PGSTATS_HASH] = "PgStatsHash",
-	[LWTRANCHE_PGSTATS_DATA] = "PgStatsData",
-	[LWTRANCHE_LAUNCHER_DSA] = "LogicalRepLauncherDSA",
-	[LWTRANCHE_LAUNCHER_HASH] = "LogicalRepLauncherHash",
-	[LWTRANCHE_DSM_REGISTRY_DSA] = "DSMRegistryDSA",
-	[LWTRANCHE_DSM_REGISTRY_HASH] = "DSMRegistryHash",
-	[LWTRANCHE_COMMITTS_SLRU] = "CommitTsSLRU",
-	[LWTRANCHE_MULTIXACTOFFSET_SLRU] = "MultiXactOffsetSLRU",
-	[LWTRANCHE_MULTIXACTMEMBER_SLRU] = "MultiXactMemberSLRU",
-	[LWTRANCHE_NOTIFY_SLRU] = "NotifySLRU",
-	[LWTRANCHE_SERIAL_SLRU] = "SerialSLRU",
-	[LWTRANCHE_SUBTRANS_SLRU] = "SubtransSLRU",
-	[LWTRANCHE_XACT_SLRU] = "XactSLRU",
-	[LWTRANCHE_PARALLEL_VACUUM_DSA] = "ParallelVacuumDSA",
-	[LWTRANCHE_AIO_URING_COMPLETION] = "AioUringCompletion",
 };
 
 StaticAssertDecl(lengthof(BuiltinTrancheNames) ==

src/backend/utils/activity/wait_event_names.txt

@@ -356,9 +356,13 @@ AioWorkerSubmissionQueue	"Waiting to access AIO worker submission queue."
 #
 # END OF PREDEFINED LWLOCKS (DO NOT CHANGE THIS LINE)
 #
-# Predefined LWLocks (i.e., those declared in lwlocknames.h) must be listed
+# Predefined LWLocks (i.e., those declared at the top of lwlocknames.h) must be
-# in the section above and must be listed in the same order as in
+# listed in the section above and must be listed in the same order as in
-# lwlocknames.h.  Other LWLocks must be listed in the section below.
+# lwlocknames.h.
+#
+# Likewise, the built-in LWLock tranches (i.e., those declared at the bottom of
+# lwlocknames.h) must be listed in the section below and must be listed in the
+# same order as in lwlocknames.h.
 #
 
 XactBuffer	"Waiting for I/O on a transaction status SLRU buffer."

src/include/storage/lwlock.h

@@ -176,51 +176,23 @@ extern void LWLockInitialize(LWLock *lock, int tranche_id);
  * Every tranche ID less than NUM_INDIVIDUAL_LWLOCKS is reserved; also,
  * we reserve additional tranche IDs for builtin tranches not included in
  * the set of individual LWLocks.  A call to LWLockNewTrancheId will never
- * return a value less than LWTRANCHE_FIRST_USER_DEFINED.
+ * return a value less than LWTRANCHE_FIRST_USER_DEFINED.  The actual list of
+ * built-in tranches is kept in lwlocklist.h.
  */
 typedef enum BuiltinTrancheIds
 {
-	LWTRANCHE_XACT_BUFFER = NUM_INDIVIDUAL_LWLOCKS,
+	/*
-	LWTRANCHE_COMMITTS_BUFFER,
+	 * LWTRANCHE_INVALID is an unused value that only exists to initialize the
-	LWTRANCHE_SUBTRANS_BUFFER,
+	 * rest of the tranches to appropriate values.
-	LWTRANCHE_MULTIXACTOFFSET_BUFFER,
+	 */
-	LWTRANCHE_MULTIXACTMEMBER_BUFFER,
+	LWTRANCHE_INVALID = NUM_INDIVIDUAL_LWLOCKS - 1,
-	LWTRANCHE_NOTIFY_BUFFER,
+
-	LWTRANCHE_SERIAL_BUFFER,
+#define PG_LWLOCK(id, name)
-	LWTRANCHE_WAL_INSERT,
+#define PG_LWLOCKTRANCHE(id, name) LWTRANCHE_##id,
-	LWTRANCHE_BUFFER_CONTENT,
+#include "storage/lwlocklist.h"
-	LWTRANCHE_REPLICATION_ORIGIN_STATE,
+#undef PG_LWLOCK
-	LWTRANCHE_REPLICATION_SLOT_IO,
+#undef PG_LWLOCKTRANCHE
-	LWTRANCHE_LOCK_FASTPATH,
+
-	LWTRANCHE_BUFFER_MAPPING,
-	LWTRANCHE_LOCK_MANAGER,
-	LWTRANCHE_PREDICATE_LOCK_MANAGER,
-	LWTRANCHE_PARALLEL_HASH_JOIN,
-	LWTRANCHE_PARALLEL_BTREE_SCAN,
-	LWTRANCHE_PARALLEL_QUERY_DSA,
-	LWTRANCHE_PER_SESSION_DSA,
-	LWTRANCHE_PER_SESSION_RECORD_TYPE,
-	LWTRANCHE_PER_SESSION_RECORD_TYPMOD,
-	LWTRANCHE_SHARED_TUPLESTORE,
-	LWTRANCHE_SHARED_TIDBITMAP,
-	LWTRANCHE_PARALLEL_APPEND,
-	LWTRANCHE_PER_XACT_PREDICATE_LIST,
-	LWTRANCHE_PGSTATS_DSA,
-	LWTRANCHE_PGSTATS_HASH,
-	LWTRANCHE_PGSTATS_DATA,
-	LWTRANCHE_LAUNCHER_DSA,
-	LWTRANCHE_LAUNCHER_HASH,
-	LWTRANCHE_DSM_REGISTRY_DSA,
-	LWTRANCHE_DSM_REGISTRY_HASH,
-	LWTRANCHE_COMMITTS_SLRU,
-	LWTRANCHE_MULTIXACTMEMBER_SLRU,
-	LWTRANCHE_MULTIXACTOFFSET_SLRU,
-	LWTRANCHE_NOTIFY_SLRU,
-	LWTRANCHE_SERIAL_SLRU,
-	LWTRANCHE_SUBTRANS_SLRU,
-	LWTRANCHE_XACT_SLRU,
-	LWTRANCHE_PARALLEL_VACUUM_DSA,
-	LWTRANCHE_AIO_URING_COMPLETION,
 	LWTRANCHE_FIRST_USER_DEFINED,
 }			BuiltinTrancheIds;
 

src/include/storage/lwlocklist.h

@@ -2,9 +2,10 @@
  *
  * lwlocklist.h
  *
- * The predefined LWLock list is kept in its own source file for use by
+ * The list of predefined LWLocks and built-in LWLock tranches is kept in
- * automatic tools.  The exact representation of a keyword is determined by
+ * its own source file for use by automatic tools.  The exact
- * the PG_LWLOCK macro, which is not defined in this file; it can be
+ * representation of a keyword is determined by the PG_LWLOCK and
+ * PG_LWLOCKTRANCHE macros, which are not defined in this file; they can be
  * defined by the caller for special purposes.
  *
  * Also, generate-lwlocknames.pl processes this file to create lwlocknames.h.
@@ -84,3 +85,53 @@ PG_LWLOCK(50, DSMRegistry)
 PG_LWLOCK(51, InjectionPoint)
 PG_LWLOCK(52, SerialControl)
 PG_LWLOCK(53, AioWorkerSubmissionQueue)
+
+/*
+ * There also exist several built-in LWLock tranches.  As with the predefined
+ * LWLocks, be sure to update the WaitEventLWLock section of
+ * src/backend/utils/activity/wait_event_names.txt when modifying this list.
+ *
+ * Note that the IDs here (the first value) don't include the LWTRANCHE_
+ * prefix.  It's added elsewhere.
+ */
+PG_LWLOCKTRANCHE(XACT_BUFFER, XactBuffer)
+PG_LWLOCKTRANCHE(COMMITTS_BUFFER, CommitTsBuffer)
+PG_LWLOCKTRANCHE(SUBTRANS_BUFFER, SubtransBuffer)
+PG_LWLOCKTRANCHE(MULTIXACTOFFSET_BUFFER, MultiXactOffsetBuffer)
+PG_LWLOCKTRANCHE(MULTIXACTMEMBER_BUFFER, MultiXactMemberBuffer)
+PG_LWLOCKTRANCHE(NOTIFY_BUFFER, NotifyBuffer)
+PG_LWLOCKTRANCHE(SERIAL_BUFFER, SerialBuffer)
+PG_LWLOCKTRANCHE(WAL_INSERT, WALInsert)
+PG_LWLOCKTRANCHE(BUFFER_CONTENT, BufferContent)
+PG_LWLOCKTRANCHE(REPLICATION_ORIGIN_STATE, ReplicationOriginState)
+PG_LWLOCKTRANCHE(REPLICATION_SLOT_IO, ReplicationSlotIO)
+PG_LWLOCKTRANCHE(LOCK_FASTPATH, LockFastPath)
+PG_LWLOCKTRANCHE(BUFFER_MAPPING, BufferMapping)
+PG_LWLOCKTRANCHE(LOCK_MANAGER, LockManager)
+PG_LWLOCKTRANCHE(PREDICATE_LOCK_MANAGER, PredicateLockManager)
+PG_LWLOCKTRANCHE(PARALLEL_HASH_JOIN, ParallelHashJoin)
+PG_LWLOCKTRANCHE(PARALLEL_BTREE_SCAN, ParallelBtreeScan)
+PG_LWLOCKTRANCHE(PARALLEL_QUERY_DSA, ParallelQueryDSA)
+PG_LWLOCKTRANCHE(PER_SESSION_DSA, PerSessionDSA)
+PG_LWLOCKTRANCHE(PER_SESSION_RECORD_TYPE, PerSessionRecordType)
+PG_LWLOCKTRANCHE(PER_SESSION_RECORD_TYPMOD, PerSessionRecordTypmod)
+PG_LWLOCKTRANCHE(SHARED_TUPLESTORE, SharedTupleStore)
+PG_LWLOCKTRANCHE(SHARED_TIDBITMAP, SharedTidBitmap)
+PG_LWLOCKTRANCHE(PARALLEL_APPEND, ParallelAppend)
+PG_LWLOCKTRANCHE(PER_XACT_PREDICATE_LIST, PerXactPredicateList)
+PG_LWLOCKTRANCHE(PGSTATS_DSA, PgStatsDSA)
+PG_LWLOCKTRANCHE(PGSTATS_HASH, PgStatsHash)
+PG_LWLOCKTRANCHE(PGSTATS_DATA, PgStatsData)
+PG_LWLOCKTRANCHE(LAUNCHER_DSA, LogicalRepLauncherDSA)
+PG_LWLOCKTRANCHE(LAUNCHER_HASH, LogicalRepLauncherHash)
+PG_LWLOCKTRANCHE(DSM_REGISTRY_DSA, DSMRegistryDSA)
+PG_LWLOCKTRANCHE(DSM_REGISTRY_HASH, DSMRegistryHash)
+PG_LWLOCKTRANCHE(COMMITTS_SLRU, CommitTsSLRU)
+PG_LWLOCKTRANCHE(MULTIXACTOFFSET_SLRU, MultiXactOffsetSLRU)
+PG_LWLOCKTRANCHE(MULTIXACTMEMBER_SLRU, MultiXactMemberSLRU)
+PG_LWLOCKTRANCHE(NOTIFY_SLRU, NotifySLRU)
+PG_LWLOCKTRANCHE(SERIAL_SLRU, SerialSLRU)
+PG_LWLOCKTRANCHE(SUBTRANS_SLRU, SubtransSLRU)
+PG_LWLOCKTRANCHE(XACT_SLRU, XactSLRU)
+PG_LWLOCKTRANCHE(PARALLEL_VACUUM_DSA, ParallelVacuumDSA)
+PG_LWLOCKTRANCHE(AIO_URING_COMPLETION, AioUringCompletion)