linux-kernel - Re: [PATCH 2/3] perf build: Use libtraceevent from the system

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Date:   Tue, 6 Dec 2022 14:22:15 -0800
From:   Ian Rogers <irogers@...gle.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        bpf@...r.kernel.org, Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 2/3] perf build: Use libtraceevent from the system

On Tue, Dec 6, 2022 at 9:31 AM Arnaldo Carvalho de Melo <acme@...nel.org> wrote:
>
> Em Tue, Dec 06, 2022 at 02:13:48PM -0300, Arnaldo Carvalho de Melo escreveu:
> > Em Tue, Dec 06, 2022 at 02:07:32PM -0300, Arnaldo Carvalho de Melo escreveu:
> > > Em Tue, Dec 06, 2022 at 02:01:43PM -0300, Arnaldo Carvalho de Melo escreveu:
> > > > Em Tue, Dec 06, 2022 at 01:41:41PM -0300, Arnaldo Carvalho de Melo escreveu:
> > > > >  Now to look at the BUILD_BPF_SKEL=1 kaboom:
> > > > >
> > > > >  [acme@...co perf]$ alias m
> > > > > alias m='rm -rf ~/libexec/perf-core/ ; make -k NO_LIBTRACEEVENT=1 BUILD_BPF_SKEL=1 O=/tmp/build/perf -C tools/perf install-bin && perf test python'
> > > > > [acme@...co perf]$ m
> > > > > make: Entering directory '/home/acme/git/perf/tools/perf'
> > > > >   BUILD:   Doing 'make -j8' parallel build
> > > > >   <SNIP>
> > > > > /usr/bin/ld: /tmp/build/perf/perf-in.o: in function `add_work':
> > > > > /home/acme/git/perf/tools/perf/util/bpf_kwork.c:285: undefined reference to `perf_kwork_add_work'
> > > > > /usr/bin/ld: /tmp/build/perf/perf-in.o: in function `lock_contention_read':
> > >
> > > For that bpf_kwork.c see below. Now to see why the python binding is not
> > > building, I guess is unrelated and you have some other outstanding
> > > patch?
> >
> > Its related:
> >
> > [acme@...co perf]$ perf test -v python
> > Couldn't bump rlimit(MEMLOCK), failures may take place when creating BPF maps, etc
> >  14: 'import perf' in python                                         :
> > --- start ---
> > test child forked, pid 1669872
> > python usage test: "echo "import sys ; sys.path.append('/tmp/build/perf/python'); import perf" | '/usr/bin/python3' "
> > Traceback (most recent call last):
> >   File "<stdin>", line 1, in <module>
> > ImportError: /tmp/build/perf/python/perf.cpython-310-x86_64-linux-gnu.so: undefined symbol: tep_unload_plugins
> > test child finished with -1
> > ---- end ----
> > 'import perf' in python: FAILED!
> > [acme@...co perf]$
> >
> > Now checking why NO_LIBTRACEEVENT=1 fails with this...
> >
> > [acme@...co perf]$ find tools/perf/ -name "*.c" | xargs grep tep_unload_plugins
> > tools/perf/util/trace-event.c:        tep_unload_plugins(t->plugin_list, t->pevent);
> > [acme@...co perf]$
> >
> > [acme@...co perf]$ grep trace-event tools/perf/util/python-ext-sources
> > util/trace-event.c
> > [acme@...co perf]$
> >
> > Trying to fix...
>
> I'm missing some detail, this isn't working, util/trace-event.c is still
> being built and linked.
>
> The python binding should be usable without tracepoints, in fact its
> first usage was just to have access to the perf metaevents, see
> tools/perf/python/twatch.py.

You're right. I'd assumed that if you were disabling libtraceevent
then you'd also disable python. To fix the issue above you can do:

--- a/tools/perf/util/python-ext-sources
+++ b/tools/perf/util/python-ext-sources
@@ -30,7 +30,6 @@ util/rblist.c
util/counts.c
util/print_binary.c
util/strlist.c
-util/trace-event.c
../lib/rbtree.c
util/string.c
util/symbol_fprintf.c

but this needs making conditional (possibly in setup.py) on whether
libtraceevent is present or not.

Thanks,
Ian

> diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
> index f0e4daeef8120853..5bd67d54d036f281 100644
> --- a/tools/perf/Makefile.perf
> +++ b/tools/perf/Makefile.perf
> @@ -348,6 +348,10 @@ export PYTHON_EXTBUILD_LIB PYTHON_EXTBUILD_TMP
>  python-clean := $(call QUIET_CLEAN, python) $(RM) -r $(PYTHON_EXTBUILD) $(OUTPUT)python/perf*.so
>
>  PYTHON_EXT_SRCS := $(shell grep -v ^\# util/python-ext-sources)
> +ifneq ($(CONFIG_TRACEEVENT),y)
> +  PYTHON_EXT_SRCS := $(call filter-out,$(PYTHON_EXT_SRCS),util/trace-event.c)
> +endif
> +
>  PYTHON_EXT_DEPS := util/python-ext-sources util/setup.py $(LIBAPI)
>
>  SCRIPTS = $(patsubst %.sh,%,$(SCRIPT_SH))
> diff --git a/tools/perf/util/python.c b/tools/perf/util/python.c
> index 728fe2f51759eb0d..72088aec2857b316 100644
> --- a/tools/perf/util/python.c
> +++ b/tools/perf/util/python.c
> @@ -1330,6 +1330,9 @@ static struct {
>  static PyObject *pyrf__tracepoint(struct pyrf_evsel *pevsel,
>                                   PyObject *args, PyObject *kwargs)
>  {
> +#ifndef HAVE_LIBTRACEEVENT
> +       return NULL;
> +#else
>         struct tep_event *tp_format;
>         static char *kwlist[] = { "sys", "name", NULL };
>         char *sys  = NULL;
> @@ -1344,6 +1347,7 @@ static PyObject *pyrf__tracepoint(struct pyrf_evsel *pevsel,
>                 return _PyLong_FromLong(-1);
>
>         return _PyLong_FromLong(tp_format->id);
> +#endif // HAVE_LIBTRACEEVENT
>  }
>
>  static PyMethodDef perf__methods[] = {