[PATCH v4 3/3] selftests/tracing: Add hist poll() support test

Masami Hiramatsu (Google)
2024-08-16T02:31:16Z

From: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Add a testcase for poll() on hist file. This introduces a helper binary
to the ftracetest, because there is no good way to reliably execute
poll() on hist file.

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
Changes in v4:
- Use getopt() in poll.c (command options are changed)
- Update test code according to the new command options.
Changes in v2:
- Update poll command to support both of POLLIN and POLLPRI, and timeout.
- Identify unsupported stable kernel if poll-in returns soon.
- Test both of POLLIN and POLLPRI.
---
tools/testing/selftests/ftrace/Makefile | 2 +
tools/testing/selftests/ftrace/poll.c | 74 ++++++++++++++++++++
.../ftrace/test.d/trigger/trigger-hist-poll.tc | 74 ++++++++++++++++++++
3 files changed, 150 insertions(+)
create mode 100644 tools/testing/selftests/ftrace/poll.c
create mode 100644 tools/testing/selftests/ftrace/test.d/trigger/trigger-hist-poll.tc

diff --git a/tools/testing/selftests/ftrace/Makefile b/tools/testing/selftests/ftrace/Makefile
index a1e955d2de4c..49d96bb16355 100644
--- a/tools/testing/selftests/ftrace/Makefile
+++ b/tools/testing/selftests/ftrace/Makefile
@@ -6,4 +6,6 @@ TEST_PROGS := ftracetest-ktap
TEST_FILES := test.d settings
EXTRA_CLEAN := $(OUTPUT)/logs/*

+TEST_GEN_PROGS = poll
+
include ../lib.mk
diff --git a/tools/testing/selftests/ftrace/poll.c b/tools/testing/selftests/ftrace/poll.c
new file mode 100644
index 000000000000..584f159654b1
--- /dev/null
+++ b/tools/testing/selftests/ftrace/poll.c
@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Simple poll on a file.
+ *
+ * Copyright (c) 2024 Google LLC.
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <poll.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#define BUFSIZE 4096
+
+/*
+ * Usage:
+ * poll [-I|-P] [-t timeout] FILE
+ */
+int main(int argc, char *argv[])
+{
+ struct pollfd pfd = {.events = POLLIN};
+ char buf[BUFSIZE];
+ int timeout = -1;
+ int ret, opt;
+
+ while ((opt = getopt(argc, argv, "IPt:")) != -1) {
+ switch (opt) {
+ case 'I':
+ pfd.events = POLLIN;
+ break;
+ case 'P':
+ pfd.events = POLLPRI;
+ break;
+ case 't':
+ timeout = atoi(optarg);
+ break;
+ default:
+ fprintf(stderr, "Usage: %s [-I|-P] [-t timeout] FILE\n",
+ argv[0]);
+ return -1;
+ }
+ }
+ if (optind >= argc) {
+ fprintf(stderr, "Error: Polling file is not specified\n");
+ return -1;
+ }
+
+ pfd.fd = open(argv[optind], O_RDONLY);
+ if (pfd.fd < 0) {
+ fprintf(stderr, "failed to open %s", argv[optind]);
+ perror("open");
+ return -1;
+ }
+
+ /* Reset poll by read if POLLIN is specified. */
+ if (pfd.events & POLLIN)
+ do {} while (read(pfd.fd, buf, BUFSIZE) == BUFSIZE);
+
+ ret = poll(&pfd, 1, timeout);
+ if (ret < 0 && errno != EINTR) {
+ perror("poll");
+ return -1;
+ }
+ close(pfd.fd);
+
+ /* If timeout happned, return code is 0 */
+ if (ret == 0)
+ return 1;
+
+ return 0;
+}
diff --git a/tools/testing/selftests/ftrace/test.d/trigger/trigger-hist-poll.tc b/tools/testing/selftests/ftrace/test.d/trigger/trigger-hist-poll.tc
new file mode 100644
index 000000000000..cbd01a71ecad
--- /dev/null
+++ b/tools/testing/selftests/ftrace/test.d/trigger/trigger-hist-poll.tc
@@ -0,0 +1,74 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+# description: event trigger - test poll wait on histogram
+# requires: set_event events/sched/sched_process_free/trigger events/sched/sched_process_free/hist
+# flags: instance
+
+POLL=${FTRACETEST_ROOT}/poll
+
+if [ ! -x ${POLL} ]; then
+ echo "poll program is not compiled!"
+ exit_unresolved
+fi
+
+EVENT=events/sched/sched_process_free/
+
+# Check poll ops is supported. Before implementing poll on hist file, it
+# returns soon with POLLIN | POLLOUT, but not POLLPRI.
+
+# This must wait >1 sec and return 1 (timeout).
+set +e
+${POLL} -I -t 1000 ${EVENT}/hist
+ret=$?
+set -e
+if [ ${ret} != 1 ]; then
+ echo "poll on hist file is not supported"
+ exit_unsupported
+fi
+
+# Test POLLIN
+echo > trace
+echo "hist:key=comm" > ${EVENT}/trigger
+echo 1 > ${EVENT}/enable
+
+# This sleep command will exit after 2 seconds.
+sleep 2 &
+BGPID=$!
+# if timeout happens, poll returns 1.
+${POLL} -I -t 4000 ${EVENT}/hist
+echo 0 > tracing_on
+
+if [ -d /proc/${BGPID} ]; then
+ echo "poll exits too soon"
+ kill -KILL ${BGPID} ||:
+ exit_fail
+fi
+
+if ! grep -qw "sleep" trace; then
+ echo "poll exits before event happens"
+ exit_fail
+fi
+
+# Test POLLPRI
+echo > trace
+echo 1 > tracing_on
+
+# This sleep command will exit after 2 seconds.
+sleep 2 &
+BGPID=$!
+# if timeout happens, poll returns 1.
+${POLL} -P -t 4000 ${EVENT}/hist
+echo 0 > tracing_on
+
+if [ -d /proc/${BGPID} ]; then
+ echo "poll exits too soon"
+ kill -KILL ${BGPID} ||:
+ exit_fail
+fi
+
+if ! grep -qw "sleep" trace; then
+ echo "poll exits before event happens"
+ exit_fail
+fi
+
+exit_pass