linux-kernel - [PATCH 28/91] perf evlist: Allow reusing the side band thread for more purposes

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Date:   Wed,  6 May 2020 12:21:31 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     Jiri Olsa <jolsa@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
        Clark Williams <williams@...hat.com>,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Song Liu <songliubraving@...com>
Subject: [PATCH 28/91] perf evlist: Allow reusing the side band thread for more purposes

From: Arnaldo Carvalho de Melo <acme@...hat.com>

I.e. so far we had just one event in that side band thread, a dummy one
with attr.bpf_event set, so that 'perf record' can go ahead and ask the
kernel for further information about BPF programs being loaded.

Allow for more than one event to be there, so that we can use it as
well for the upcoming --switch-output-event feature.

Acked-by: Jiri Olsa <jolsa@...hat.com>
Cc: Adrian Hunter <adrian.hunter@...el.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Song Liu <songliubraving@...com>
Link: http://lore.kernel.org/lkml/20200429131106.27974-6-acme@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/util/evlist.h          |  1 +
 tools/perf/util/sideband_evlist.c | 23 +++++++++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
index a9d01a11570a..93de63e2a247 100644
--- a/tools/perf/util/evlist.h
+++ b/tools/perf/util/evlist.h
@@ -111,6 +111,7 @@ int perf_evlist__add_sb_event(struct evlist *evlist,
 			      struct perf_event_attr *attr,
 			      perf_evsel__sb_cb_t cb,
 			      void *data);
+void evlist__set_cb(struct evlist *evlist, perf_evsel__sb_cb_t cb, void *data);
 int perf_evlist__start_sb_thread(struct evlist *evlist,
 				 struct target *target);
 void perf_evlist__stop_sb_thread(struct evlist *evlist);
diff --git a/tools/perf/util/sideband_evlist.c b/tools/perf/util/sideband_evlist.c
index 073d201bb6ea..1d6f470d64c4 100644
--- a/tools/perf/util/sideband_evlist.c
+++ b/tools/perf/util/sideband_evlist.c
@@ -4,6 +4,7 @@
 #include "util/evlist.h"
 #include "util/evsel.h"
 #include "util/mmap.h"
+#include "util/perf_api_probe.h"
 #include <perf/mmap.h>
 #include <linux/perf_event.h>
 #include <limits.h>
@@ -80,6 +81,19 @@ static void *perf_evlist__poll_thread(void *arg)
 	return NULL;
 }
 
+void evlist__set_cb(struct evlist *evlist, perf_evsel__sb_cb_t cb, void *data)
+{
+	struct evsel *evsel;
+
+	evlist__for_each_entry(evlist, evsel) {
+		evsel->core.attr.sample_id_all    = 1;
+		evsel->core.attr.watermark        = 1;
+		evsel->core.attr.wakeup_watermark = 1;
+		evsel->side_band.cb   = cb;
+		evsel->side_band.data = data;
+      }
+}
+
 int perf_evlist__start_sb_thread(struct evlist *evlist, struct target *target)
 {
 	struct evsel *counter;
@@ -90,6 +104,15 @@ int perf_evlist__start_sb_thread(struct evlist *evlist, struct target *target)
 	if (perf_evlist__create_maps(evlist, target))
 		goto out_delete_evlist;
 
+	if (evlist->core.nr_entries > 1) {
+		bool can_sample_identifier = perf_can_sample_identifier();
+
+		evlist__for_each_entry(evlist, counter)
+			perf_evsel__set_sample_id(counter, can_sample_identifier);
+
+		perf_evlist__set_id_pos(evlist);
+	}
+
 	evlist__for_each_entry(evlist, counter) {
 		if (evsel__open(counter, evlist->core.cpus, evlist->core.threads) < 0)
 			goto out_delete_evlist;
-- 
2.21.1