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Date:   Tue, 6 Dec 2022 14:31:12 -0300
From:   Arnaldo Carvalho de Melo <acme@kernel.org>
To:     Ian Rogers <irogers@google.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org,
        bpf@vger.kernel.org, Stephane Eranian <eranian@google.com>
Subject: Re: [PATCH 2/3] perf build: Use libtraceevent from the system
Message-ID: <Y498YP2N3gvFSr/X@kernel.org>
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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@quaco 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@quaco 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@quaco 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@quaco perf]$
> 
> Now checking why NO_LIBTRACEEVENT=1 fails with this...
> 
> [acme@quaco 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@quaco perf]$
> 
> [acme@quaco perf]$ grep trace-event tools/perf/util/python-ext-sources
> util/trace-event.c
> [acme@quaco 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.

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[] = {