perf intel-tpebs: Add mutex for tpebs_results

Ensure sample reader isn't racing with events being added/removed.

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/20250414174134.3095492-12-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 8cbb3b3c00564bd45877ebf6a45e5cb223fed532..44e86d0f934322fcdf1769ee52d52988e75a9573 100644 (file)
--- a/tools/perf/util/intel-tpebs.c
+++ b/tools/perf/util/intel-tpebs.c
@@ -16,6 +16,7 @@
 #include "debug.h"
 #include "evlist.h"
 #include "evsel.h"
+#include "mutex.h"
 #include "session.h"
 #include "tool.h"
 #include "cpumap.h"
@@ -32,6 +33,7 @@ bool tpebs_recording;
 static LIST_HEAD(tpebs_results);
 static pthread_t tpebs_reader_thread;
 static struct child_process tpebs_cmd;
+static struct mutex tpebs_mtx;
 
 struct tpebs_retire_lat {
        struct list_head nd;
@@ -51,6 +53,19 @@ struct tpebs_retire_lat {
 
 static struct tpebs_retire_lat *tpebs_retire_lat__find(struct evsel *evsel);
 
+static void tpebs_mtx_init(void)
+{
+       mutex_init(&tpebs_mtx);
+}
+
+static struct mutex *tpebs_mtx_get(void)
+{
+       static pthread_once_t tpebs_mtx_once = PTHREAD_ONCE_INIT;
+
+       pthread_once(&tpebs_mtx_once, tpebs_mtx_init);
+       return &tpebs_mtx;
+}
+
 static int evsel__tpebs_start_perf_record(struct evsel *evsel, int control_fd[], int ack_fd[])
 {
        const char **record_argv;
@@ -59,13 +74,15 @@ static int evsel__tpebs_start_perf_record(struct evsel *evsel, int control_fd[],
        char cpumap_buf[50];
        struct tpebs_retire_lat *t;
 
+       mutex_lock(tpebs_mtx_get());
        list_for_each_entry(t, &tpebs_results, nd)
                tpebs_event_size++;
 
        record_argv = malloc((10 + 2 * tpebs_event_size) * sizeof(*record_argv));
-       if (!record_argv)
+       if (!record_argv) {
+               mutex_unlock(tpebs_mtx_get());
                return -ENOMEM;
-
+       }
        record_argv[i++] = "perf";
        record_argv[i++] = "record";
        record_argv[i++] = "-W";
@@ -101,6 +118,7 @@ static int evsel__tpebs_start_perf_record(struct evsel *evsel, int control_fd[],
        list_for_each_entry(t, &tpebs_results, nd)
                t->started = true;
 
+       mutex_unlock(tpebs_mtx_get());
        return ret;
 }
 
@@ -112,9 +130,12 @@ static int process_sample_event(const struct perf_tool *tool __maybe_unused,
 {
        struct tpebs_retire_lat *t;
 
+       mutex_lock(tpebs_mtx_get());
        t = tpebs_retire_lat__find(evsel);
-       if (!t)
+       if (!t) {
+               mutex_unlock(tpebs_mtx_get());
                return -EINVAL;
+       }
        /*
         * Need to handle per core results? We are assuming average retire
         * latency value will be used. Save the number of samples and the sum of
@@ -123,6 +144,7 @@ static int process_sample_event(const struct perf_tool *tool __maybe_unused,
        t->count += 1;
        t->sum += sample->retire_lat;
        t->val = (double) t->sum / t->count;
+       mutex_unlock(tpebs_mtx_get());
        return 0;
 }
 
@@ -229,7 +251,6 @@ static struct tpebs_retire_lat *tpebs_retire_lat__new(struct evsel *evsel)
                return NULL;
        }
        result->evsel = evsel;
-       list_add_tail(&result->nd, &tpebs_results);
        return result;
 }
 
@@ -282,15 +303,22 @@ static struct tpebs_retire_lat *tpebs_retire_lat__find(struct evsel *evsel)
 static int evsel__tpebs_prepare(struct evsel *evsel)
 {
        struct evsel *pos;
-       struct tpebs_retire_lat *tpebs_event = tpebs_retire_lat__find(evsel);
+       struct tpebs_retire_lat *tpebs_event;
 
+       mutex_lock(tpebs_mtx_get());
+       tpebs_event = tpebs_retire_lat__find(evsel);
        if (tpebs_event) {
                /* evsel, or an identically named one, was already prepared. */
+               mutex_unlock(tpebs_mtx_get());
                return 0;
        }
        tpebs_event = tpebs_retire_lat__new(evsel);
-       if (!tpebs_event)
+       if (!tpebs_event) {
+               mutex_unlock(tpebs_mtx_get());
                return -ENOMEM;
+       }
+       list_add_tail(&tpebs_event->nd, &tpebs_results);
+       mutex_unlock(tpebs_mtx_get());
 
        /*
         * Eagerly prepare all other evsels on the list to try to ensure that by
@@ -317,6 +345,7 @@ static int evsel__tpebs_prepare(struct evsel *evsel)
 int evsel__tpebs_open(struct evsel *evsel)
 {
        int ret;
+       bool tpebs_empty;
 
        /* We should only run tpebs_start when tpebs_recording is enabled. */
        if (!tpebs_recording)
@@ -336,7 +365,10 @@ int evsel__tpebs_open(struct evsel *evsel)
        if (ret)
                return ret;
 
-       if (!list_empty(&tpebs_results)) {
+       mutex_lock(tpebs_mtx_get());
+       tpebs_empty = list_empty(&tpebs_results);
+       mutex_unlock(tpebs_mtx_get());
+       if (!tpebs_empty) {
                struct pollfd pollfd = { .events = POLLIN, };
                int control_fd[2], ack_fd[2], len;
                char ack_buf[8];
@@ -436,8 +468,10 @@ int evsel__tpebs_read(struct evsel *evsel, int cpu_map_idx, int thread)
         */
        tpebs_stop();
 
+       mutex_lock(tpebs_mtx_get());
        t = tpebs_retire_lat__find(evsel);
        val = rint(t->val);
+       mutex_unlock(tpebs_mtx_get());
 
        if (old_count) {
                count->val = old_count->val + val;
@@ -460,9 +494,13 @@ int evsel__tpebs_read(struct evsel *evsel, int cpu_map_idx, int thread)
  */
 void evsel__tpebs_close(struct evsel *evsel)
 {
-       struct tpebs_retire_lat *t = tpebs_retire_lat__find(evsel);
+       struct tpebs_retire_lat *t;
 
+       mutex_lock(tpebs_mtx_get());
+       t = tpebs_retire_lat__find(evsel);
+       list_del_init(&t->nd);
        tpebs_retire_lat__delete(t);
+       mutex_unlock(tpebs_mtx_get());
 
        if (list_empty(&tpebs_results))
                tpebs_stop();