Hi,
On Mon, Mar 18, 2024 at 08:49:34AM -0700, Noah Misch wrote:
> On Mon, Mar 18, 2024 at 09:04:44AM +0000, Bertrand Drouvot wrote:
> > --- a/src/backend/utils/activity/wait_event_names.txt
> > +++ b/src/backend/utils/activity/wait_event_names.txt
> > @@ -24,7 +24,12 @@
> > # SGML tables of wait events for inclusion in the documentation.
> > #
> > # When adding a new wait event, make sure it is placed in the appropriate
> > -# ClassName section.
> > +# ClassName section. If the wait event is backpatched to a version < 17
> > then
> > +# put it under a "Backpatch" delimiter at the end of the related ClassName
> > +# section.
>
> Back-patch from v17 to pre-v17 won't use this, because v16 has hand-maintained
> enums. It's back-patch v18->v17 or v22->v17 where this will come up.
Thanks for looking at it!
Oh right, the comment is wrong, re-worded in v2 attached.
Regards,
--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com
>From 868d97a853c45639685198c9090cedd77dc4b9af Mon Sep 17 00:00:00 2001
From: Bertrand Drouvot <bertranddrouvot...@gmail.com>
Date: Mon, 18 Mar 2024 08:34:19 +0000
Subject: [PATCH v2] Add "Backpatch" regions in wait_event_names.txt
When backpatching, adding an event will renumber others, which can make an
extension report the wrong event until recompiled. This is due to the fact that
generate-wait_event_types.pl sorts events to position them. The "Backpatch"
region added here ensures no ordering is done for the wait events found after
this delimiter.
---
.../activity/generate-wait_event_types.pl | 26 ++++++++++++++++++-
.../utils/activity/wait_event_names.txt | 19 +++++++++++++-
2 files changed, 43 insertions(+), 2 deletions(-)
100.0% src/backend/utils/activity/
diff --git a/src/backend/utils/activity/generate-wait_event_types.pl b/src/backend/utils/activity/generate-wait_event_types.pl
index f1adf0e8e7..d129d94889 100644
--- a/src/backend/utils/activity/generate-wait_event_types.pl
+++ b/src/backend/utils/activity/generate-wait_event_types.pl
@@ -38,7 +38,9 @@ die "Not possible to specify --docs and --code simultaneously"
open my $wait_event_names, '<', $ARGV[0] or die;
+my @backpatch_lines;
my @lines;
+my $backpatch = 0;
my $section_name;
my $note;
my $note_name;
@@ -59,10 +61,26 @@ while (<$wait_event_names>)
{
$section_name = $_;
$section_name =~ s/^.*- //;
+ $backpatch = 0;
next;
}
- push(@lines, $section_name . "\t" . $_);
+ # Are we dealing with backpatch wait events?
+ if (/^Backpatch:$/)
+ {
+ $backpatch = 1;
+ next;
+ }
+
+ # Backpatch wait events won't be sorted during code generation
+ if ($gen_code && $backpatch)
+ {
+ push(@backpatch_lines, $section_name . "\t" . $_);
+ }
+ else
+ {
+ push(@lines, $section_name . "\t" . $_);
+ }
}
# Sort the lines based on the second column.
@@ -70,6 +88,12 @@ while (<$wait_event_names>)
my @lines_sorted =
sort { uc((split(/\t/, $a))[1]) cmp uc((split(/\t/, $b))[1]) } @lines;
+# If we are generating code then concat @lines_sorted and @backpatch_lines.
+if ($gen_code)
+{
+ push(@lines_sorted, @backpatch_lines);
+}
+
# Read the sorted lines and populate the hash table
foreach my $line (@lines_sorted)
{
diff --git a/src/backend/utils/activity/wait_event_names.txt b/src/backend/utils/activity/wait_event_names.txt
index c08e00d1d6..b6303a0fdb 100644
--- a/src/backend/utils/activity/wait_event_names.txt
+++ b/src/backend/utils/activity/wait_event_names.txt
@@ -24,7 +24,11 @@
# SGML tables of wait events for inclusion in the documentation.
#
# When adding a new wait event, make sure it is placed in the appropriate
-# ClassName section.
+# ClassName section. If the wait event is backpatched from master to a version
+# >= 17 then put it under a "Backpatch:" delimiter at the end of the related
+# ClassName section (on the non master branches) or at its natural position on
+# the master branch.
+# Ensure that the backpatch regions are always empty on the master branch.
#
# WaitEventLWLock and WaitEventLock have their own C code for their wait event
# enums and function names. Hence, for these, only the SGML documentation is
@@ -61,6 +65,7 @@ WAL_SENDER_MAIN "Waiting in main loop of WAL sender process."
WAL_SUMMARIZER_WAL "Waiting in WAL summarizer for more WAL to be generated."
WAL_WRITER_MAIN "Waiting in main loop of WAL writer process."
+Backpatch:
#
# Wait Events - Client
@@ -82,6 +87,7 @@ WAIT_FOR_STANDBY_CONFIRMATION "Waiting for WAL to be received and flushed by the
WAL_SENDER_WAIT_FOR_WAL "Waiting for WAL to be flushed in WAL sender process."
WAL_SENDER_WRITE_DATA "Waiting for any activity when processing replies from WAL receiver in WAL sender process."
+Backpatch:
#
# Wait Events - IPC
@@ -149,6 +155,7 @@ WAL_RECEIVER_WAIT_START "Waiting for startup process to send initial data for st
WAL_SUMMARY_READY "Waiting for a new WAL summary to be generated."
XACT_GROUP_UPDATE "Waiting for the group leader to update transaction status at end of a parallel operation."
+Backpatch:
#
# Wait Events - Timeout
@@ -169,6 +176,7 @@ VACUUM_DELAY "Waiting in a cost-based vacuum delay point."
VACUUM_TRUNCATE "Waiting to acquire an exclusive lock to truncate off any empty pages at the end of a table vacuumed."
WAL_SUMMARIZER_ERROR "Waiting after a WAL summarizer error."
+Backpatch:
#
# Wait Events - IO
@@ -256,6 +264,7 @@ WAL_SYNC "Waiting for a WAL file to reach durable storage."
WAL_SYNC_METHOD_ASSIGN "Waiting for data to reach durable storage while assigning a new WAL sync method."
WAL_WRITE "Waiting for a write to a WAL file."
+Backpatch:
#
# Wait Events - Buffer Pin
@@ -265,6 +274,7 @@ Section: ClassName - WaitEventBufferPin
BUFFER_PIN "Waiting to acquire an exclusive pin on a buffer."
+Backpatch:
#
# Wait Events - Extension
@@ -274,6 +284,8 @@ Section: ClassName - WaitEventExtension
Extension "Waiting in an extension."
+Backpatch:
+
#
# Wait Events - LWLock
#
@@ -330,6 +342,8 @@ DSMRegistry "Waiting to read or update the dynamic shared memory registry."
InjectionPoint "Waiting to read or update information related to injection points."
SerialControl "Waiting to read or update shared <filename>pg_serial</filename> state."
+# Don't create a Backpatch region here.
+
#
# END OF PREDEFINED LWLOCKS (DO NOT CHANGE THIS LINE)
#
@@ -377,6 +391,7 @@ SerialSLRU "Waiting to access the serializable transaction conflict SLRU cache."
SubtransSLRU "Waiting to access the sub-transaction SLRU cache."
XactSLRU "Waiting to access the transaction status SLRU cache."
+# Don't create a Backpatch region here.
#
# Wait Events - Lock
@@ -399,3 +414,5 @@ object "Waiting to acquire a lock on a non-relation database object."
userlock "Waiting to acquire a user lock."
advisory "Waiting to acquire an advisory user lock."
applytransaction "Waiting to acquire a lock on a remote transaction being applied by a logical replication subscriber."
+
+Backpatch:
--
2.34.1
