linux-kernel - [PATCH v2 16/16] perf parse-events: Tidy the setting of the default event name

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Message-Id: <20240416061533.921723-17-irogers@google.com>
Date: Mon, 15 Apr 2024 23:15:32 -0700
From: Ian Rogers <irogers@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	Kan Liang <kan.liang@...ux.intel.com>, James Clark <james.clark@....com>, 
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org, 
	bpf@...r.kernel.org, Atish Patra <atishp@...osinc.com>, linux-riscv@...ts.infradead.org, 
	Beeman Strong <beeman@...osinc.com>
Subject: [PATCH v2 16/16] perf parse-events: Tidy the setting of the default
 event name

Add comments. Pass ownership of the event name to save on a strdup.

Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/perf/util/parse-events.c |  9 ++++++---
 tools/perf/util/parse-events.h |  2 +-
 tools/perf/util/parse-events.l |  5 +++++
 tools/perf/util/parse-events.y | 10 +++++++---
 4 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index 1c1b1bcb78e8..0f308b4db2b9 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -1836,18 +1836,21 @@ int parse_events__modifier_event(struct parse_events_state *parse_state, void *l
 	return parse_events__modifier_list(parse_state, loc, list, mod, /*group=*/false);
 }
 
-int parse_events_name(struct list_head *list, const char *name)
+int parse_events__set_default_name(struct list_head *list, char *name)
 {
 	struct evsel *evsel;
+	bool used_name = false;
 
 	__evlist__for_each_entry(list, evsel) {
 		if (!evsel->name) {
-			evsel->name = strdup(name);
+			evsel->name = used_name ? strdup(name) : name;
+			used_name = true;
 			if (!evsel->name)
 				return -ENOMEM;
 		}
 	}
-
+	if (!used_name)
+		free(name);
 	return 0;
 }
 
diff --git a/tools/perf/util/parse-events.h b/tools/perf/util/parse-events.h
index 0bb5f0c80a5e..5695308efab9 100644
--- a/tools/perf/util/parse-events.h
+++ b/tools/perf/util/parse-events.h
@@ -207,7 +207,7 @@ int parse_events__modifier_event(struct parse_events_state *parse_state, void *l
 				 struct list_head *list, struct parse_events_modifier mod);
 int parse_events__modifier_group(struct parse_events_state *parse_state, void *loc,
 				 struct list_head *list, struct parse_events_modifier mod);
-int parse_events_name(struct list_head *list, const char *name);
+int parse_events__set_default_name(struct list_head *list, char *name);
 int parse_events_add_tracepoint(struct list_head *list, int *idx,
 				const char *sys, const char *event,
 				struct parse_events_error *error,
diff --git a/tools/perf/util/parse-events.l b/tools/perf/util/parse-events.l
index 4aaf0c53d9b6..08ea2d845dc3 100644
--- a/tools/perf/util/parse-events.l
+++ b/tools/perf/util/parse-events.l
@@ -96,6 +96,11 @@ static int drv_str(yyscan_t scanner, int token)
 	return token;
 }
 
+/*
+ * Use yyless to return all the characaters to the input. Update the column for
+ * location debugging. If __alloc is non-zero set yylval to the text for the
+ * returned token's value.
+ */
 #define REWIND(__alloc)				\
 do {								\
 	YYSTYPE *__yylval = parse_events_get_lval(yyscanner);	\
diff --git a/tools/perf/util/parse-events.y b/tools/perf/util/parse-events.y
index 6f1042272dda..68b3b06c7ff0 100644
--- a/tools/perf/util/parse-events.y
+++ b/tools/perf/util/parse-events.y
@@ -247,10 +247,14 @@ event_name
 event_name:
 PE_EVENT_NAME event_def
 {
-	int err;
+	/*
+	 * When an event is parsed the text is rewound and the entire text of
+	 * the event is set to the str of PE_EVENT_NAME token matched here. If
+	 * no name was on an event via a term, set the name to the entire text
+	 * taking ownership of the allocation.
+	 */
+	int err = parse_events__set_default_name($2, $1);
 
-	err = parse_events_name($2, $1);
-	free($1);
 	if (err) {
 		free_list_evsel($2);
 		YYNOMEM;
-- 
2.44.0.683.g7961c838ac-goog