perf lock: Redo __cmd_report

This function should be straightforward, and we can remove some trivial
logic by moving the functionality of read_events() into __cmd_report() -
thus allowing a new session to be properly deleted.

Since the 'info' subcommand also needs to process the recorded events,
add a 'display_info' flag to differentiate between report and info
commands.

Furthermore, this patch also calls perf_session__has_traces(), making
sure that we don't compare apples and oranges, fixing a segfault when
using an perf.data file generated by a different subcommand. ie:

./perf mem record sleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.017 MB perf.data (~724 samples) ]

./perf lock report
Segmentation fault (core dumped)

Signed-off-by: Davidlohr Bueso <davidlohr@hp.com>
Cc: Aswin Chandramouleeswaran <aswin@hp.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Hitoshi Mitake <mitake@dcl.info.waseda.ac.jp>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1378693159-8747-5-git-send-email-davidlohr@hp.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-lock.c

@@ -818,6 +818,18 @@ static int process_sample_event(struct perf_tool *tool __maybe_unused,
 	return 0;
 }
 
+static void sort_result(void)
+{
+	unsigned int i;
+	struct lock_stat *st;
+
+	for (i = 0; i < LOCKHASH_SIZE; i++) {
+		list_for_each_entry(st, &lockhash_table[i], hash_entry) {
+			insert_to_result(st, compare);
+		}
+	}
+}
+
 static const struct perf_evsel_str_handler lock_tracepoints[] = {
 	{ "lock:lock_acquire",	 perf_evsel__process_lock_acquire,   }, /* CONFIG_LOCKDEP */
 	{ "lock:lock_acquired",	 perf_evsel__process_lock_acquired,  }, /* CONFIG_LOCKDEP, CONFIG_LOCK_STAT */
@@ -825,51 +837,47 @@ static const struct perf_evsel_str_handler lock_tracepoints[] = {
 	{ "lock:lock_release",	 perf_evsel__process_lock_release,   }, /* CONFIG_LOCKDEP */
 };
 
-static int read_events(void)
+static int __cmd_report(bool display_info)
 {
+	int err = -EINVAL;
 	struct perf_tool eops = {
 		.sample		 = process_sample_event,
 		.comm		 = perf_event__process_comm,
 		.ordered_samples = true,
 	};
+
 	session = perf_session__new(input_name, O_RDONLY, 0, false, &eops);
 	if (!session) {
 		pr_err("Initializing perf session failed\n");
-		return -1;
+		return -ENOMEM;
 	}
 
+	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");
-		return -1;
+		goto out_delete;
 	}
 
-	return perf_session__process_events(session, &eops);
-}
+	if (select_key())
+		goto out_delete;
 
-static void sort_result(void)
-{
-	unsigned int i;
-	struct lock_stat *st;
-
-	for (i = 0; i < LOCKHASH_SIZE; i++) {
-		list_for_each_entry(st, &lockhash_table[i], hash_entry) {
-			insert_to_result(st, compare);
-		}
-	}
-}
+	err = perf_session__process_events(session, &eops);
+	if (err)
+		goto out_delete;
 
-static int __cmd_report(void)
-{
 	setup_pager();
+	if (display_info) /* used for info subcommand */
+		err = dump_info();
+	else {
+		sort_result();
+		print_result();
+	}
 
-	if ((select_key() != 0) ||
-	    (read_events() != 0))
-		return -1;
-
-	sort_result();
-	print_result();
-
-	return 0;
+out_delete:
+	perf_session__delete(session);
+	return err;
 }
 
 static int __cmd_record(int argc, const char **argv)
@@ -970,7 +978,7 @@ int cmd_lock(int argc, const char **argv, const char *prefix __maybe_unused)
 			if (argc)
 				usage_with_options(report_usage, report_options);
 		}
-		__cmd_report();
+		rc = __cmd_report(false);
 	} else if (!strcmp(argv[0], "script")) {
 		/* Aliased to 'perf script' */
 		return cmd_script(argc, argv, prefix);
@@ -983,11 +991,7 @@ int cmd_lock(int argc, const char **argv, const char *prefix __maybe_unused)
 		}
 		/* recycling report_lock_ops */
 		trace_handler = &report_lock_ops;
-		setup_pager();
-		if (read_events() != 0)
-			rc = -1;
-		else
-			rc = dump_info();
+		rc = __cmd_report(true);
 	} else {
 		usage_with_options(lock_usage, lock_options);
 	}