linux-kernel - [PATCH AUTOSEL 4.19 058/177] perf trace: Filter own pid to avoid a feedback look in 'perf trace record -a'

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Date:   Tue, 10 Dec 2019 16:30:22 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Arnaldo Carvalho de Melo <acme@...hat.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        David Ahern <dsahern@...il.com>, Jiri Olsa <jolsa@...nel.org>,
        Luis Cláudio Gonçalves 
        <lclaudio@...hat.com>, Namhyung Kim <namhyung@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 4.19 058/177] perf trace: Filter own pid to avoid a feedback look in 'perf trace record -a'

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

[ Upstream commit 7fbfe22cf4cfe01a88704dd76ca65d108039d297 ]

When doing a system wide 'perf trace record' we need, just like in 'perf
trace' live mode, to filter out perf trace's own pid, so set up a
tracepoint filter for the raw_syscalls tracepoints right after adding
them to the argv array that is set up to then call cmd_record().

Reported-by: Andi Kleen <ak@...ux.intel.com>
Cc: Adrian Hunter <adrian.hunter@...el.com>
Cc: David Ahern <dsahern@...il.com>
Cc: Jiri Olsa <jolsa@...nel.org>
Cc: Luis Cláudio Gonçalves <lclaudio@...hat.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Link: https://lkml.kernel.org/n/tip-uysx5w8f2y5ndoln5cq370tv@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 tools/perf/builtin-trace.c | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 3f43aedb384d4..7ec3fc4dc5edf 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -2209,21 +2209,23 @@ static int trace__record(struct trace *trace, int argc, const char **argv)
 		"-m", "1024",
 		"-c", "1",
 	};
-
+	pid_t pid = getpid();
+	char *filter = asprintf__tp_filter_pids(1, &pid);
 	const char * const sc_args[] = { "-e", };
 	unsigned int sc_args_nr = ARRAY_SIZE(sc_args);
 	const char * const majpf_args[] = { "-e", "major-faults" };
 	unsigned int majpf_args_nr = ARRAY_SIZE(majpf_args);
 	const char * const minpf_args[] = { "-e", "minor-faults" };
 	unsigned int minpf_args_nr = ARRAY_SIZE(minpf_args);
+	int err = -1;
 
-	/* +1 is for the event string below */
-	rec_argc = ARRAY_SIZE(record_args) + sc_args_nr + 1 +
+	/* +3 is for the event string below and the pid filter */
+	rec_argc = ARRAY_SIZE(record_args) + sc_args_nr + 3 +
 		majpf_args_nr + minpf_args_nr + argc;
 	rec_argv = calloc(rec_argc + 1, sizeof(char *));
 
-	if (rec_argv == NULL)
-		return -ENOMEM;
+	if (rec_argv == NULL || filter == NULL)
+		goto out_free;
 
 	j = 0;
 	for (i = 0; i < ARRAY_SIZE(record_args); i++)
@@ -2240,11 +2242,13 @@ static int trace__record(struct trace *trace, int argc, const char **argv)
 			rec_argv[j++] = "syscalls:sys_enter,syscalls:sys_exit";
 		else {
 			pr_err("Neither raw_syscalls nor syscalls events exist.\n");
-			free(rec_argv);
-			return -1;
+			goto out_free;
 		}
 	}
 
+	rec_argv[j++] = "--filter";
+	rec_argv[j++] = filter;
+
 	if (trace->trace_pgfaults & TRACE_PFMAJ)
 		for (i = 0; i < majpf_args_nr; i++)
 			rec_argv[j++] = majpf_args[i];
@@ -2256,7 +2260,11 @@ static int trace__record(struct trace *trace, int argc, const char **argv)
 	for (i = 0; i < (unsigned int)argc; i++)
 		rec_argv[j++] = argv[i];
 
-	return cmd_record(j, rec_argv);
+	err = cmd_record(j, rec_argv);
+out_free:
+	free(filter);
+	free(rec_argv);
+	return err;
 }
 
 static size_t trace__fprintf_thread_summary(struct trace *trace, FILE *fp);
-- 
2.20.1