[PATCH] perf lock: Allow concurrent record and report

[Namhyung Kim]

To support live monitoring of kernel lock contention without BPF,
it should support something like below:

  # perf lock record -a -o- sleep 1 | perf lock contention -i-
   contended   total wait     max wait     avg wait         type   caller

           2     10.27 us      6.17 us      5.13 us     spinlock   load_balance+0xc03
           1      5.29 us      5.29 us      5.29 us     rwlock:W   ep_scan_ready_list+0x54
           1      4.12 us      4.12 us      4.12 us     spinlock   smpboot_thread_fn+0x116
           1      3.28 us      3.28 us      3.28 us        mutex   pipe_read+0x50

To do that, it needs to handle HEAD_ATTR, HEADER_EVENT_UPDATE and
HEADER_TRACING_DATA which are generated only for the pipe mode.
And setting event handler also should be delayed until it gets the
event information.

Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
---
 tools/perf/builtin-lock.c                 | 68 +++++++++++++++--------
 tools/perf/tests/shell/lock_contention.sh | 15 ++++-
 2 files changed, 60 insertions(+), 23 deletions(-)

diff --git a/tools/perf/builtin-lock.c b/tools/perf/builtin-lock.c
index 6f79175365a8..0d280093b19a 100644
--- a/tools/perf/builtin-lock.c
+++ b/tools/perf/builtin-lock.c
@@ -1390,6 +1390,34 @@ static int dump_info(void)
 	return rc;
 }
 
+static const struct evsel_str_handler lock_tracepoints[] = {
+	{ "lock:lock_acquire",	 evsel__process_lock_acquire,   }, /* CONFIG_LOCKDEP */
+	{ "lock:lock_acquired",	 evsel__process_lock_acquired,  }, /* CONFIG_LOCKDEP, CONFIG_LOCK_STAT */
+	{ "lock:lock_contended", evsel__process_lock_contended, }, /* CONFIG_LOCKDEP, CONFIG_LOCK_STAT */
+	{ "lock:lock_release",	 evsel__process_lock_release,   }, /* CONFIG_LOCKDEP */
+};
+
+static const struct evsel_str_handler contention_tracepoints[] = {
+	{ "lock:contention_begin", evsel__process_contention_begin, },
+	{ "lock:contention_end",   evsel__process_contention_end,   },
+};
+
+static int process_event_update(struct perf_tool *tool,
+				union perf_event *event,
+				struct evlist **pevlist)
+{
+	int ret;
+
+	ret = perf_event__process_event_update(tool, event, pevlist);
+	if (ret < 0)
+		return ret;
+
+	/* this can return -EEXIST since we call it for each evsel */
+	perf_session__set_tracepoints_handlers(session, lock_tracepoints);
+	perf_session__set_tracepoints_handlers(session, contention_tracepoints);
+	return 0;
+}
+
 typedef int (*tracepoint_handler)(struct evsel *evsel,
 				  struct perf_sample *sample);
 
@@ -1545,28 +1573,19 @@ static void print_contention_result(struct lock_contention *con)
 	print_bad_events(bad, total);
 }
 
-static const struct evsel_str_handler lock_tracepoints[] = {
-	{ "lock:lock_acquire",	 evsel__process_lock_acquire,   }, /* CONFIG_LOCKDEP */
-	{ "lock:lock_acquired",	 evsel__process_lock_acquired,  }, /* CONFIG_LOCKDEP, CONFIG_LOCK_STAT */
-	{ "lock:lock_contended", evsel__process_lock_contended, }, /* CONFIG_LOCKDEP, CONFIG_LOCK_STAT */
-	{ "lock:lock_release",	 evsel__process_lock_release,   }, /* CONFIG_LOCKDEP */
-};
-
-static const struct evsel_str_handler contention_tracepoints[] = {
-	{ "lock:contention_begin", evsel__process_contention_begin, },
-	{ "lock:contention_end",   evsel__process_contention_end,   },
-};
-
 static bool force;
 
 static int __cmd_report(bool display_info)
 {
 	int err = -EINVAL;
 	struct perf_tool eops = {
+		.attr		 = perf_event__process_attr,
+		.event_update	 = process_event_update,
 		.sample		 = process_sample_event,
 		.comm		 = perf_event__process_comm,
 		.mmap		 = perf_event__process_mmap,
 		.namespaces	 = perf_event__process_namespaces,
+		.tracing_data	 = perf_event__process_tracing_data,
 		.ordered_events	 = true,
 	};
 	struct perf_data data = {
@@ -1585,17 +1604,19 @@ static int __cmd_report(bool display_info)
 	symbol_conf.sort_by_name = true;
 	symbol__init(&session->header.env);
 
-	if (!perf_session__has_traces(session, "lock record"))
-		goto out_delete;
+	if (!data.is_pipe) {
+		if (!perf_session__has_traces(session, "lock record"))
+			goto out_delete;
 
-	if (perf_session__set_tracepoints_handlers(session, lock_tracepoints)) {
-		pr_err("Initializing perf session tracepoint handlers failed\n");
-		goto out_delete;
-	}
+		if (perf_session__set_tracepoints_handlers(session, lock_tracepoints)) {
+			pr_err("Initializing perf session tracepoint handlers failed\n");
+			goto out_delete;
+		}
 
-	if (perf_session__set_tracepoints_handlers(session, contention_tracepoints)) {
-		pr_err("Initializing perf session tracepoint handlers failed\n");
-		goto out_delete;
+		if (perf_session__set_tracepoints_handlers(session, contention_tracepoints)) {
+			pr_err("Initializing perf session tracepoint handlers failed\n");
+			goto out_delete;
+		}
 	}
 
 	if (setup_output_field(false, output_fields))
@@ -1633,9 +1654,12 @@ static int __cmd_contention(int argc, const char **argv)
 {
 	int err = -EINVAL;
 	struct perf_tool eops = {
+		.attr		 = perf_event__process_attr,
+		.event_update	 = process_event_update,
 		.sample		 = process_sample_event,
 		.comm		 = perf_event__process_comm,
 		.mmap		 = perf_event__process_mmap,
+		.tracing_data	 = perf_event__process_tracing_data,
 		.ordered_events	 = true,
 	};
 	struct perf_data data = {
@@ -1698,7 +1722,7 @@ static int __cmd_contention(int argc, const char **argv)
 			pr_err("lock contention BPF setup failed\n");
 			goto out_delete;
 		}
-	} else {
+	} else if (!data.is_pipe) {
 		if (!perf_session__has_traces(session, "lock record"))
 			goto out_delete;
 
diff --git a/tools/perf/tests/shell/lock_contention.sh b/tools/perf/tests/shell/lock_contention.sh
index 04bf604e3c6f..f7bd0d8eb5c3 100755
--- a/tools/perf/tests/shell/lock_contention.sh
+++ b/tools/perf/tests/shell/lock_contention.sh
@@ -53,7 +53,7 @@ test_bpf()
 
 	if ! perf lock con -b true > /dev/null 2>&1 ; then
 		echo "[Skip] No BPF support"
-		exit
+		return
 	fi
 
 	# the perf lock contention output goes to the stderr
@@ -65,9 +65,22 @@ test_bpf()
 	fi
 }
 
+test_record_concurrent()
+{
+	echo "Testing perf lock record and perf lock contention at the same time"
+	perf lock record -o- -- perf bench sched messaging 2> /dev/null | \
+	perf lock contention -i- -E 1 -q 2> ${result}
+	if [ $(cat "${result}" | wc -l) != "1" ]; then
+		echo "[Fail] Recorded result count is not 1:" $(cat "${result}" | wc -l)
+		err=1
+		exit
+	fi
+}
+
 check
 
 test_record
 test_bpf
+test_record_concurrent
 
 exit ${err}
-- 
2.38.1.431.g37b22c650d-goog