Re: make BuiltinTrancheNames less ugly

On Wed Jan 24, 2024 at 8:09 AM CST, Alvaro Herrera wrote:
> From 3d24b89855888a6650ec1aafb3579d810bfec5ac Mon Sep 17 00:00:00 2001
> From: Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>
> Date: Tue, 23 Jan 2024 10:36:14 +0100
> Subject: [PATCH] Remove IndividualLWLockNames
>
> We can just merge the lwlock names into the BuiltinTrancheNames array.
> This requires that Meson compiles the file with -I. in CPPFLAGS, which
> in turn requires some additional contortions for DTrace support in
> FreeBSD.
> ---
> src/backend/meson.build | 4 +++-
> src/backend/storage/lmgr/Makefile | 3 ++-
> src/backend/storage/lmgr/generate-lwlocknames.pl | 10 ++--------
> src/backend/storage/lmgr/lwlock.c | 13 ++++---------
> src/backend/storage/lmgr/meson.build | 12 ++++++++++--
> 5 files changed, 21 insertions(+), 21 deletions(-)
>
> diff --git a/src/backend/meson.build b/src/backend/meson.build
> index 8767aaba67..57a52c37e0 100644
> --- a/src/backend/meson.build
> +++ b/src/backend/meson.build
> @@ -127,7 +127,9 @@ backend_objs = [postgres_lib.extract_all_objects(recursive: false)]
> if dtrace.found() and host_system != 'darwin'
> backend_input += custom_target(
> 'probes.o',
> - input: ['utils/probes.d', postgres_lib.extract_objects(backend_sources, timezone_sources)],
> + input: ['utils/probes.d',
> + postgres_lib.extract_objects(backend_sources, timezone_sources),
> + lwlock_lib.extract_objects(lwlock_source)],
> output: 'probes.o',
> command: [dtrace, '-C', '-G', '-o', '@OUTPUT@', '-s', '@INPUT@'],
> install: false,
> diff --git a/src/backend/storage/lmgr/Makefile b/src/backend/storage/lmgr/Makefile
> index 504480e847..81da6ee13a 100644
> --- a/src/backend/storage/lmgr/Makefile
> +++ b/src/backend/storage/lmgr/Makefile
> @@ -12,13 +12,14 @@ subdir = src/backend/storage/lmgr
> top_builddir = ../../../..
> include $(top_builddir)/src/Makefile.global
>
> +override CPPFLAGS := -I. $(CPPFLAGS)
> +
> OBJS = \
> condition_variable.o \
> deadlock.o \
> lmgr.o \
> lock.o \
> lwlock.o \
> - lwlocknames.o \
> predicate.o \
> proc.o \
> s_lock.o \
> diff --git a/src/backend/storage/lmgr/generate-lwlocknames.pl b/src/backend/storage/lmgr/generate-lwlocknames.pl
> index 7b93ecf6c1..a679a4ff54 100644
> --- a/src/backend/storage/lmgr/generate-lwlocknames.pl
> +++ b/src/backend/storage/lmgr/generate-lwlocknames.pl
> @@ -10,7 +10,6 @@ use Getopt::Long;
> my $output_path = '.';
>
> my $lastlockidx = -1;
> -my $continue = "\n";
>
> GetOptions('outdir:s' => \$output_path);
>
> @@ -29,8 +28,6 @@ print $h $autogen;
> print $h "/* there is deliberately not an #ifndef LWLOCKNAMES_H here */\n\n";
> print $c $autogen, "\n";
>
> -print $c "const char *const IndividualLWLockNames[] = {";
> -
> #
> # First, record the predefined LWLocks listed in wait_event_names.txt. We'll
> # cross-check those with the ones in lwlocknames.txt.
> @@ -97,12 +94,10 @@ while (<$lwlocknames>)
> while ($lastlockidx < $lockidx - 1)
> {
> ++$lastlockidx;
> - printf $c "%s \"<unassigned:%d>\"", $continue, $lastlockidx;
> - $continue = ",\n";
> + printf $c "[%s] = \"<unassigned:%d>\",\n", $lastlockidx, $lastlockidx;
> }
> - printf $c "%s \"%s\"", $continue, $trimmedlockname;
> + printf $c "[%s] = \"%s\",\n", $lockidx, $trimmedlockname;
> $lastlockidx = $lockidx;
> - $continue = ",\n";
>
> print $h "#define $lockname (&MainLWLockArray[$lockidx].lock)\n";
> }
> @@ -112,7 +107,6 @@ die
> . "lwlocknames.txt"
> if $i < scalar @wait_event_lwlocks;
>
> -printf $c "\n};\n";
> print $h "\n";
> printf $h "#define NUM_INDIVIDUAL_LWLOCKS %s\n", $lastlockidx + 1;
>
> diff --git a/src/backend/storage/lmgr/lwlock.c b/src/backend/storage/lmgr/lwlock.c
> index 98fa6035cc..8aad9c6690 100644
> --- a/src/backend/storage/lmgr/lwlock.c
> +++ b/src/backend/storage/lmgr/lwlock.c
> @@ -115,8 +115,8 @@ StaticAssertDecl(LW_VAL_EXCLUSIVE > (uint32) MAX_BACKENDS,
> * There are three sorts of LWLock "tranches":
> *
> * 1. The individually-named locks defined in lwlocknames.h each have their
> - * own tranche. The names of these tranches appear in IndividualLWLockNames[]
> - * in lwlocknames.c.
> + * own tranche. The names of these tranches come from lwlocknames.c into
> + * BuiltinTranchNames[] below.
> *
> * 2. There are some predefined tranches for built-in groups of locks.
> * These are listed in enum BuiltinTrancheIds in lwlock.h, and their names
> @@ -129,9 +129,8 @@ StaticAssertDecl(LW_VAL_EXCLUSIVE > (uint32) MAX_BACKENDS,
> * All these names are user-visible as wait event names, so choose with care
> * ... and do not forget to update the documentation's list of wait events.
> */
> -extern const char *const IndividualLWLockNames[]; /* in lwlocknames.c */
> -
> static const char *const BuiltinTrancheNames[] = {
> +#include "lwlocknames.c"
> [LWTRANCHE_XACT_BUFFER] = "XactBuffer",
> [LWTRANCHE_COMMITTS_BUFFER] = "CommitTsBuffer",
> [LWTRANCHE_SUBTRANS_BUFFER] = "SubtransBuffer",
> @@ -738,11 +737,7 @@ LWLockReportWaitEnd(void)
> static const char *
> GetLWTrancheName(uint16 trancheId)
> {
> - /* Individual LWLock? */
> - if (trancheId < NUM_INDIVIDUAL_LWLOCKS)
> - return IndividualLWLockNames[trancheId];
> -
> - /* Built-in tranche? */
> + /* Individual LWLock or built-in tranche? */
> if (trancheId < LWTRANCHE_FIRST_USER_DEFINED)
> return BuiltinTrancheNames[trancheId];
>
> diff --git a/src/backend/storage/lmgr/meson.build b/src/backend/storage/lmgr/meson.build
> index da32198f78..a12064ae8a 100644
> --- a/src/backend/storage/lmgr/meson.build
> +++ b/src/backend/storage/lmgr/meson.build
> @@ -5,11 +5,19 @@ backend_sources += files(
> 'deadlock.c',
> 'lmgr.c',
> 'lock.c',
> - 'lwlock.c',
> 'predicate.c',
> 'proc.c',
> 's_lock.c',
> 'spin.c',
> )
>
> -generated_backend_sources += lwlocknames[1]
> +# this includes a .c file generated. Is there a better way?
> +lwlock_source = files('lwlock.c')

I don't understand this comment. Could you explain it a bit more?

> +
> +lwlock_lib = static_library('lwlock',
> + lwlock_source,
> + dependencies: [backend_code],
> + include_directories: include_directories('../../../include/storage'),
> + kwargs: internal_lib_args,
> + )

Move the paren to the beginning of the line.

> +backend_link_with += lwlock_lib

Earlier in the thread you had said this:

> IMO it would be less ugly to have the origin file lwlocknames.txt be
> not a text file but a .h with a macro that can be defined by
> interested parties so that they can extract what they want from the
> file, like PG_CMDTAG or PG_KEYWORD. Using Perl for this seems dirty...

I really like this idea, and would definitely be more inclined to see
a solution like this.

--
Tristan Partin
Neon (https://neon.tech)