linux-kernel - Re: [PATCH v3 2/2] perf jevents: Autogenerate empty-pmu-events.c

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Message-ID: <ZqpcRIzzBb5KC6Zb@x1>
Date: Wed, 31 Jul 2024 12:46:12 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Ian Rogers <irogers@...gle.com>
Cc: John Garry <john.g.garry@...cle.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>, Namhyung Kim <namhyung@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Kan Liang <kan.liang@...ux.intel.com>,
	Jing Zhang <renyu.zj@...ux.alibaba.com>,
	Xu Yang <xu.yang_2@....com>, Sandipan Das <sandipan.das@....com>,
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	philip.li@...el.com, oliver.sang@...el.com,
	Weilin Wang <weilin.wang@...el.com>
Subject: Re: [PATCH v3 2/2] perf jevents: Autogenerate empty-pmu-events.c

On Wed, Jul 31, 2024 at 12:33:50PM -0300, Arnaldo Carvalho de Melo wrote:
> On Wed, Jul 31, 2024 at 07:08:18AM -0700, Ian Rogers wrote:
> > On Wed, Jul 31, 2024 at 6:18 AM Arnaldo Carvalho de Melo
> > <acme@...nel.org> wrote:
> > >
> > > On Tue, Jul 30, 2024 at 12:17:44PM -0700, Ian Rogers wrote:
> > > > empty-pmu-events.c exists so that builds may occur without python
> > > > being installed on a system. Manually updating empty-pmu-events.c to
> > > > be in sync with jevents.py is a pain, let's use jevents.py to generate
> > > > empty-pmu-events.c.
> > >
> > > What am I missing here?
> > >
> > > If it exists so that we can build on a system without python how can we
> > > use python to generate it?
> > >
> > > Now having python in the system is a requirement and thus we don't need
> > > empty-pmu-events.c anymore?
> > >
> > > Can you guys please clarify that?
> > 
> > The requirement for python hasn't changed.
> > 
> > Case 1: no python or NO_JEVENTS=1
> > Build happens using empty-pmu-events.c that is checked in, no python
> > is required.
> > 
> > Case 2: python
> > pmu-events.c is created by jevents.py (requiring python) and then built.
> > This change adds a step where the empty-pmu-events.c is created using
> > jevents.py and that file is diffed against the checked in version.
> > This stops the checked in empty-pmu-events.c diverging if changes are
> > made to jevents.py. If the diff causes the build to fail then you just
> > copy the diff empty-pmu-events.c over the checked in one.
> 
> I'll try and add your explanation to the log message, thanks for
> clarifying it!

So, with it in place I'm now noticing:

⬢[acme@...lbox perf-tools-next]$ rm -rf /tmp/build/$(basename $PWD)/ ; mkdir -p /tmp/build/$(basename $PWD)/
⬢[acme@...lbox perf-tools-next]$ alias m='rm -rf ~/libexec/perf-core/ ; make -k CORESIGHT=1 O=/tmp/build/$(basename $PWD)/ -C tools/perf install-bin && perf test python'
⬢[acme@...lbox perf-tools-next]$ m
<SNIP>
  GEN     /tmp/build/perf-tools-next/pmu-events/test-empty-pmu-events.c
  MKDIR   /tmp/build/perf-tools-next/arch/x86/util/
  CC      /tmp/build/perf-tools-next/util/annotate.o
  CC      /tmp/build/perf-tools-next/arch/x86/util/tsc.o
  CC      /tmp/build/perf-tools-next/arch/x86/tests/hybrid.o
  CC      /tmp/build/perf-tools-next/util/block-info.o
  CC      /tmp/build/perf-tools-next/arch/x86/tests/intel-pt-test.o
  CC      /tmp/build/perf-tools-next/arch/x86/util/pmu.o
  MKDIR   /tmp/build/perf-tools-next/ui/browsers/
  CC      /tmp/build/perf-tools-next/ui/browsers/annotate.o
  CC      /tmp/build/perf-tools-next/builtin-kallsyms.o
  CC      /tmp/build/perf-tools-next/util/block-range.o
  TEST    /tmp/build/perf-tools-next/pmu-events/empty-pmu-events.log
--- pmu-events/empty-pmu-events.c	2024-07-31 12:44:14.355042296 -0300
+++ /tmp/build/perf-tools-next/pmu-events/test-empty-pmu-events.c	2024-07-31 12:45:35.048682785 -0300
@@ -380,7 +380,7 @@
                         continue;
 
                 ret = pmu_events_table__for_each_event_pmu(table, table_pmu, fn, data);
-                if (pmu || ret)
+                if (ret)
                         return ret;
         }
         return 0;
  CC      /tmp/build/perf-tools-next/tests/openat-syscall.o
make[3]: *** [pmu-events/Build:42: /tmp/build/perf-tools-next/pmu-events/empty-pmu-events.log] Error 1
make[3]: *** Deleting file '/tmp/build/perf-tools-next/pmu-events/empty-pmu-events.log'
make[2]: *** [Makefile.perf:763: /tmp/build/perf-tools-next/pmu-events/pmu-events-in.o] Error 2
make[2]: *** Waiting for unfinished jobs....
  CC      /tmp/build/perf-tools-next/arch/x86/util/kvm-stat.o
<SNIP>