perf test arm-spe: Check if perf-record hangs when recording workload with forks

Add shell test to check if perf-record hangs when recording an arm_spe
event with forks.

The test FAILS if the Kernel is not patched with Commit 961c391 ("perf:
Always wake the parent event").

Unpatched Kernel:

  $ perf test -v 90
  90: Check Arm SPE doesn't hang when there are forks
  --- start ---
  test child forked, pid 14232
  Recording workload with fork
  Log lines = 90 /tmp/__perf_test.stderr.0Nu0U
  Log lines after 1 second = 90 /tmp/__perf_test.stderr.0Nu0U
  SPE hang test: FAIL
  test child finished with -1
  ---- end ----
  Check Arm SPE trace data in workload with forks: FAILED!

Patched Kernel:

  $ perf test -v 90
  90: Check Arm SPE doesn't hang when there are forks
  --- start ---
  test child forked, pid 2930
  Compiling test program...
  Recording workload...
  Log lines = 478 /tmp/__perf_test.log.026AI
  Log lines after 1 second = 557 /tmp/__perf_test.log.026AI
  SPE hang test: PASS
  Cleaning up files...
  test child finished with 0
  ---- end ----
  Check Arm SPE trace data in workload with forks: Ok

Reviewed-by: James Clark <[email protected]>
Reviewed-by: Leo Yan <[email protected]>
Signed-off-by: German Gomez <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Namhyung Kim <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

Author: German Gomez

tools/perf/tests/shell/test_arm_spe_fork.sh

@@ -0,0 +1,92 @@
+#!/bin/sh
+# Check Arm SPE doesn't hang when there are forks
+
+# SPDX-License-Identifier: GPL-2.0
+# German Gomez <[email protected]>, 2022
+
+skip_if_no_arm_spe_event() {
+	perf list | egrep -q 'arm_spe_[0-9]+//' && return 0
+	return 2
+}
+
+skip_if_no_arm_spe_event || exit 2
+
+# skip if there's no compiler
+if ! [ -x "$(command -v cc)" ]; then
+	echo "failed: no compiler, install gcc"
+	exit 2
+fi
+
+TEST_PROGRAM_SOURCE=$(mktemp /tmp/__perf_test.program.XXXXX.c)
+TEST_PROGRAM=$(mktemp /tmp/__perf_test.program.XXXXX)
+PERF_DATA=$(mktemp /tmp/__perf_test.perf.data.XXXXX)
+PERF_RECORD_LOG=$(mktemp /tmp/__perf_test.log.XXXXX)
+
+cleanup_files()
+{
+	echo "Cleaning up files..."
+	rm -f ${PERF_RECORD_LOG}
+	rm -f ${PERF_DATA}
+	rm -f ${TEST_PROGRAM_SOURCE}
+	rm -f ${TEST_PROGRAM}
+}
+
+trap cleanup_files exit term int
+
+# compile test program
+cat << EOF > $TEST_PROGRAM_SOURCE
+#include <math.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/wait.h>
+
+int workload() {
+  while (1)
+    sqrt(rand());
+  return 0;
+}
+
+int main() {
+  switch (fork()) {
+    case 0:
+      return workload();
+    case -1:
+      return 1;
+    default:
+      wait(NULL);
+  }
+  return 0;
+}
+EOF
+
+echo "Compiling test program..."
+CFLAGS="-lm"
+cc $TEST_PROGRAM_SOURCE $CFLAGS -o $TEST_PROGRAM || exit 1
+
+echo "Recording workload..."
+perf record -o ${PERF_DATA} -e arm_spe/period=65536/ -vvv -- $TEST_PROGRAM > ${PERF_RECORD_LOG} 2>&1 &
+PERFPID=$!
+
+# Check if perf hangs by checking the perf-record logs.
+sleep 1
+log0=$(wc -l $PERF_RECORD_LOG)
+echo Log lines = $log0
+sleep 1
+log1=$(wc -l $PERF_RECORD_LOG)
+echo Log lines after 1 second = $log1
+
+kill $PERFPID
+wait $PERFPID
+# test program may leave an orphan process running the workload
+killall $(basename $TEST_PROGRAM)
+
+if [ "$log0" = "$log1" ];
+then
+        echo "SPE hang test: FAIL"
+        exit 1
+else
+        echo "SPE hang test: PASS"
+fi
+
+exit 0