perf intel-tpebs: Simplify tpebs_cmd

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.

Reviewed-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Weilin Wang <weilin.wang@intel.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexandre Torgue <alexandre.torgue@foss.st.com>
Cc: Andreas Färber <afaerber@suse.de>
Cc: Caleb Biggers <caleb.biggers@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Perry Taylor <perry.taylor@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Falcon <thomas.falcon@intel.com>
Link: https://lore.kernel.org/r/20250414174134.3095492-3-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/intel-tpebs.c b/tools/perf/util/intel-tpebs.c
index 3503da28a12f81e3a58fbae763648f655c9a4425..74b43faab9862071867753cea695d6caaa4c3ffd 100644 (file)
--- 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;
-       }
 }