perf record: Fix synthesis failure warnings

Some calls to synthesis functions set err < 0 but only warn about the
failure and continue.  However they do not set err back to zero, relying
on subsequent code to do that.

That changed with the introduction of option --synth. When --synth=no
subsequent functions that set err back to zero are not called.

Fix by setting err = 0 in those cases.

Example:

 Before:

   $ perf record --no-bpf-event --synth=all -o /tmp/huh uname
   Couldn't synthesize bpf events.
   Linux
   [ perf record: Woken up 1 times to write data ]
   [ perf record: Captured and wrote 0.014 MB /tmp/huh (7 samples) ]
   $ perf record --no-bpf-event --synth=no -o /tmp/huh uname
   Couldn't synthesize bpf events.

 After:

   $ perf record --no-bpf-event --synth=no -o /tmp/huh uname
   Couldn't synthesize bpf events.
   Linux
   [ perf record: Woken up 1 times to write data ]
   [ perf record: Captured and wrote 0.014 MB /tmp/huh (7 samples) ]

Fixes: b5be9be7740987b0 ("perf record: Add --synth option")
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20220907162458.72817-1-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 09b68d76bbdccaf2a07bb9b39a0a17c3b7183cf1..f87ef43eb8204a173901975d55da4e87426598a9 100644 (file)
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -1906,14 +1906,18 @@ static int record__synthesize(struct record *rec, bool tail)
 
        err = perf_event__synthesize_bpf_events(session, process_synthesized_event,
                                                machine, opts);
-       if (err < 0)
+       if (err < 0) {
                pr_warning("Couldn't synthesize bpf events.\n");
+               err = 0;
+       }
 
        if (rec->opts.synth & PERF_SYNTH_CGROUP) {
                err = perf_event__synthesize_cgroups(tool, process_synthesized_event,
                                                     machine);
-               if (err < 0)
+               if (err < 0) {
                        pr_warning("Couldn't synthesize cgroup events.\n");
+                       err = 0;
+               }
        }
 
        if (rec->opts.nr_threads_synthesize > 1) {