[PATCH v4 02/16] perf intel-tpebs: Simplify tpebs_cmd

Ian Rogers
2025-04-09T06:10:57Z

No need to dynamically allocate when there is 1. tpebs_pid duplicates
tpebs_cmd.pid, so remove. Use 0 as the uninitialized value (PID == 0
is reserved for the kernel) rather than -1.

Signed-off-by: Ian Rogers <irogers@google.com>
---
tools/perf/util/intel-tpebs.c | 55 ++++++++++++-----------------------
1 file changed, 18 insertions(+), 37 deletions(-)

diff --git a/tools/perf/util/intel-tpebs.c b/tools/perf/util/intel-tpebs.c
index 3503da28a12f..74b43faab986 100644
--- a/tools/perf/util/intel-tpebs.c
+++ b/tools/perf/util/intel-tpebs.c
@@ -28,11 +28,10 @@
#define PERF_DATA "-"

bool tpebs_recording;
-static pid_t tpebs_pid = -1;
static size_t tpebs_event_size;
static LIST_HEAD(tpebs_results);
static pthread_t tpebs_reader_thread;
-static struct child_process *tpebs_cmd;
+static struct child_process tpebs_cmd;

struct tpebs_retire_lat {
struct list_head nd;
@@ -83,16 +82,6 @@ static int get_perf_record_args(const char **record_argv, char buf[],
return 0;
}

-static int prepare_run_command(const char **argv)
-{
- tpebs_cmd = zalloc(sizeof(struct child_process));
- if (!tpebs_cmd)
- return -ENOMEM;
- tpebs_cmd->argv = argv;
- tpebs_cmd->out = -1;
- return 0;
-}
-
static int start_perf_record(int control_fd[], int ack_fd[],
const char *cpumap_buf)
{
@@ -110,10 +99,10 @@ static int start_perf_record(int control_fd[], int ack_fd[],
if (ret)
goto out;

- ret = prepare_run_command(record_argv);
- if (ret)
- goto out;
- ret = start_command(tpebs_cmd);
+ assert(tpebs_cmd.pid == 0);
+ tpebs_cmd.argv = record_argv;
+ tpebs_cmd.out = -1;
+ ret = start_command(&tpebs_cmd);
out:
free(record_argv);
return ret;
@@ -156,14 +145,13 @@ static int process_feature_event(struct perf_session *session,
return 0;
}

-static void *__sample_reader(void *arg)
+static void *__sample_reader(void *arg __maybe_unused)
{
- struct child_process *child = arg;
struct perf_session *session;
struct perf_data data = {
.mode = PERF_DATA_MODE_READ,
.path = PERF_DATA,
- .file.fd = child->out,
+ .file.fd = tpebs_cmd.out,
};
struct perf_tool tool;

@@ -189,12 +177,12 @@ static int tpebs_stop(void)
int ret = 0;

/* Like tpebs_start, we should only run tpebs_end once. */
- if (tpebs_pid != -1) {
- kill(tpebs_cmd->pid, SIGTERM);
- tpebs_pid = -1;
+ if (tpebs_cmd.pid != 0) {
+ kill(tpebs_cmd.pid, SIGTERM);
pthread_join(tpebs_reader_thread, NULL);
- close(tpebs_cmd->out);
- ret = finish_command(tpebs_cmd);
+ close(tpebs_cmd.out);
+ ret = finish_command(&tpebs_cmd);
+ tpebs_cmd.pid = 0;
if (ret == -ERR_RUN_COMMAND_WAITPID_SIGNAL)
ret = 0;
}
@@ -219,7 +207,7 @@ int tpebs_start(struct evlist *evsel_list)
* We should only run tpebs_start when tpebs_recording is enabled.
* And we should only run it once with all the required events.
*/
- if (tpebs_pid != -1 || !tpebs_recording)
+ if (tpebs_cmd.pid != 0 || !tpebs_recording)
return 0;

cpu_map__snprint(evsel_list->core.user_requested_cpus, cpumap_buf, sizeof(cpumap_buf));
@@ -284,10 +272,11 @@ int tpebs_start(struct evlist *evsel_list)
ret = start_perf_record(control_fd, ack_fd, cpumap_buf);
if (ret)
goto out;
- tpebs_pid = tpebs_cmd->pid;
- if (pthread_create(&tpebs_reader_thread, NULL, __sample_reader, tpebs_cmd)) {
- kill(tpebs_cmd->pid, SIGTERM);
- close(tpebs_cmd->out);
+
+ if (pthread_create(&tpebs_reader_thread, /*attr=*/NULL, __sample_reader,
+ /*arg=*/NULL)) {
+ kill(tpebs_cmd.pid, SIGTERM);
+ close(tpebs_cmd.out);
pr_err("Could not create thread to process sample data.\n");
ret = -1;
goto out;
@@ -416,18 +405,10 @@ void tpebs_delete(void)
{
struct tpebs_retire_lat *r, *rtmp;

- if (tpebs_pid == -1)
- return;
-
tpebs_stop();

list_for_each_entry_safe(r, rtmp, &tpebs_results, nd) {
list_del_init(&r->nd);
tpebs_retire_lat__delete(r);
}
-
- if (tpebs_cmd) {
- free(tpebs_cmd);
- tpebs_cmd = NULL;
- }
}
--
2.49.0.504.g3bcea36a83-goog