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

["Masami Hiramatsu (Google)" <mhiramat@kernel.org>]

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>
---
 tools/testing/selftests/ftrace/Makefile            |    3 +
 tools/testing/selftests/ftrace/poll.c              |   34 +++++++++++++++
 .../ftrace/test.d/trigger/trigger-hist-poll.tc     |   46 ++++++++++++++++++++
 3 files changed, 83 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..830b2299ea27 100644
--- a/tools/testing/selftests/ftrace/Makefile
+++ b/tools/testing/selftests/ftrace/Makefile
@@ -6,4 +6,7 @@ TEST_PROGS := ftracetest-ktap
 TEST_FILES := test.d settings
 EXTRA_CLEAN := $(OUTPUT)/logs/*
 
+LDFLAGS += -static
+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..800d1114629c
--- /dev/null
+++ b/tools/testing/selftests/ftrace/poll.c
@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Simple poll on a file.
+ *
+ * Copyright (c) 2024 Google LLC.
+ */
+
+#include <fcntl.h>
+#include <poll.h>
+#include <stdio.h>
+#include <unistd.h>
+
+#define BUFSIZE 4096
+
+int main(int argc, char *argv[])
+{
+	struct pollfd pfd = {.events = POLLPRI};
+	char buf[BUFSIZE];
+
+	if (argc < 2)
+		return -1;
+	pfd.fd = open(argv[1], O_RDONLY);
+	if (pfd.fd < 0) {
+		perror("open");
+		return -1;
+	}
+
+	if (poll(&pfd, 1, -1) < 0) {
+		perror("poll");
+		return -1;
+	}
+	close(pfd.fd);
+	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..ac3999dee40b
--- /dev/null
+++ b/tools/testing/selftests/ftrace/test.d/trigger/trigger-hist-poll.tc
@@ -0,0 +1,46 @@
+#!/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/
+
+echo "hist:key=comm" > ${EVENT}/trigger
+echo 1 > ${EVENT}/enable
+
+# setting timeout
+PID=$$
+SIG_FAIL=37
+trap exit_fail $SIG_FAIL
+sleep 10 && (kill -s ${SIG_FAIL} ${PID} ||:) &
+TOPID=$!
+
+# sleep command will exit after 2 seconds
+sleep 2 &
+BGPID=$!
+${POLL} ${EVENT}/hist
+# stop timeout
+kill -KILL ${TOPID} ||:
+
+cat trace > ${TMPDIR}/trace
+
+if [ -d /proc/${BGPID} ]; then
+  echo "poll exits too soon"
+  kill -KILL ${BGPID} ||:
+  exit_fail
+fi
+
+if ! grep -qw "sleep" ${TMPDIR}/trace; then
+  echo "poll exits before event happens"
+  exit_fail
+fi
+
+exit_pass