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Subject[PATCH 04/17] perf ftrace: Add support for --pid option
Date
From: Namhyung Kim <namhyung.kim@lge.com>

The -p (--pid) option enables to trace existing process by its pid.

Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
tools/perf/builtin-ftrace.c | 89 ++++++++++++++++++++++++++++++++-------------
1 file changed, 63 insertions(+), 26 deletions(-)

diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
index 6f3dd02c5b9a..bd415f2b1cde 100644
--- a/tools/perf/builtin-ftrace.c
+++ b/tools/perf/builtin-ftrace.c
@@ -11,6 +11,7 @@

#include <unistd.h>
#include <signal.h>
+#include <fcntl.h>

#include "util/debug.h"
#include "util/parse-options.h"
@@ -34,11 +35,12 @@ static void sig_handler(int sig __maybe_unused)
done = true;
}

-static int write_tracing_file(const char *name, const char *val)
+static int __write_tracing_file(const char *name, const char *val, bool append)
{
char *file;
int fd, ret = -1;
ssize_t size = strlen(val);
+ int flags = O_WRONLY;

file = get_tracing_file(name);
if (!file) {
@@ -46,7 +48,12 @@ static int write_tracing_file(const char *name, const char *val)
return -1;
}

- fd = open(file, O_WRONLY);
+ if (append)
+ flags |= O_APPEND;
+ else
+ flags |= O_TRUNC;
+
+ fd = open(file, flags);
if (fd < 0) {
pr_debug("cannot open tracing file: %s\n", name);
goto out;
@@ -63,6 +70,16 @@ out:
return ret;
}

+static int write_tracing_file(const char *name, const char *val)
+{
+ return __write_tracing_file(name, val, false);
+}
+
+static int append_tracing_file(const char *name, const char *val)
+{
+ return __write_tracing_file(name, val, true);
+}
+
static int reset_tracing_files(struct perf_ftrace *ftrace __maybe_unused)
{
if (write_tracing_file("tracing_on", "0") < 0)
@@ -77,11 +94,27 @@ static int reset_tracing_files(struct perf_ftrace *ftrace __maybe_unused)
return 0;
}

+static int set_tracing_pid(struct perf_ftrace *ftrace)
+{
+ int i;
+ char buf[16];
+
+ if (perf_target__has_cpu(&ftrace->target))
+ return 0;
+
+ for (i = 0; i < thread_map__nr(ftrace->evlist->threads); i++) {
+ scnprintf(buf, sizeof(buf), "%d",
+ ftrace->evlist->threads->map[i]);
+ if (append_tracing_file("set_ftrace_pid", buf) < 0)
+ return -1;
+ }
+ return 0;
+}
+
static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)
{
char *trace_file;
int trace_fd;
- char *trace_pid;
char buf[4096];
struct pollfd pollfd = {
.events = POLLIN,
@@ -92,42 +125,37 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)
return -1;
}

- if (argc < 1)
- return -1;
-
signal(SIGINT, sig_handler);
signal(SIGUSR1, sig_handler);
signal(SIGCHLD, sig_handler);

- reset_tracing_files(ftrace);
+ if (reset_tracing_files(ftrace) < 0)
+ goto out;

/* reset ftrace buffer */
if (write_tracing_file("trace", "0") < 0)
goto out;

- if (perf_evlist__prepare_workload(ftrace->evlist, &ftrace->target,
- argv, false, true) < 0)
- goto out;
-
- if (write_tracing_file("current_tracer", ftrace->tracer) < 0) {
- pr_err("failed to set current_tracer to %s\n", ftrace->tracer);
+ if (argc && perf_evlist__prepare_workload(ftrace->evlist,
+ &ftrace->target,
+ argv, false, true) < 0) {
goto out;
}

- if (asprintf(&trace_pid, "%d", ftrace->evlist->threads->map[0]) < 0) {
- pr_err("failed to allocate pid string\n");
- goto out;
+ if (set_tracing_pid(ftrace) < 0) {
+ pr_err("failed to set ftrace pid\n");
+ goto out_reset;
}

- if (write_tracing_file("set_ftrace_pid", trace_pid) < 0) {
- pr_err("failed to set pid: %s\n", trace_pid);
- goto out_free_pid;
+ if (write_tracing_file("current_tracer", ftrace->tracer) < 0) {
+ pr_err("failed to set current_tracer to %s\n", ftrace->tracer);
+ goto out_reset;
}

trace_file = get_tracing_file("trace_pipe");
if (!trace_file) {
pr_err("failed to open trace_pipe\n");
- goto out_free_pid;
+ goto out_reset;
}

trace_fd = open(trace_file, O_RDONLY);
@@ -136,7 +164,7 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)

if (trace_fd < 0) {
pr_err("failed to open trace_pipe\n");
- goto out_free_pid;
+ goto out_reset;
}

fcntl(trace_fd, F_SETFL, O_NONBLOCK);
@@ -175,11 +203,9 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)

out_close_fd:
close(trace_fd);
-out_free_pid:
- free(trace_pid);
-out:
+out_reset:
reset_tracing_files(ftrace);
-
+out:
return done ? 0 : -1;
}

@@ -197,6 +223,8 @@ int cmd_ftrace(int argc, const char **argv, const char *prefix __maybe_unused)
const struct option ftrace_options[] = {
OPT_STRING('t', "tracer", &ftrace.tracer, "tracer",
"tracer to use: function_graph or function"),
+ OPT_STRING('p', "pid", &ftrace.target.pid, "pid",
+ "trace on existing process id"),
OPT_INCR('v', "verbose", &verbose,
"be more verbose"),
OPT_END()
@@ -204,9 +232,18 @@ int cmd_ftrace(int argc, const char **argv, const char *prefix __maybe_unused)

argc = parse_options(argc, argv, ftrace_options, ftrace_usage,
PARSE_OPT_STOP_AT_NON_OPTION);
- if (!argc)
+ if (!argc && perf_target__none(&ftrace.target))
usage_with_options(ftrace_usage, ftrace_options);

+ ret = perf_target__validate(&ftrace.target);
+ if (ret) {
+ char errbuf[512];
+
+ perf_target__strerror(&ftrace.target, ret, errbuf, 512);
+ pr_err("%s\n", errbuf);
+ return -EINVAL;
+ }
+
ftrace.evlist = perf_evlist__new();
if (ftrace.evlist == NULL)
return -ENOMEM;
--
1.7.11.7


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