selftests/bpf: Add a test for objects stuck in free_by_rcu_ttracegrafted

Delete all elements of BPF_F_NO_PREALLOC hash map in one batch. The first
free_bulk() starts RCU tasks trace GP and the rest of the elements are
freed while it's in flight. Wait for call_rcu_ttrace_in_progress to clear
in bpf_mem_cache of every cpu and check that free_by_rcu_ttrace and
waiting_for_gp_ttrace lists are empty.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20260930095920.601738-4-alexei.starovoitov@gmail.com
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>

1 files changed, 59 insertions, 0 deletions

diff --git a/tools/time/udelay_test.sh b/tools/time/udelay_test.sh
new file mode 100755
index 000000000..6779d7e55
--- /dev/null
+++ b/tools/time/udelay_test.sh
@@ -0,0 +1,59 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0-only
+
+# udelay() test script
+#
+# Test is executed by writing and reading to /sys/kernel/debug/udelay_test
+# and exercises a variety of delays to ensure that udelay() is delaying
+# at least as long as requested (as compared to ktime).
+#
+# Copyright (C) 2014 Google, Inc.
+#
+
+MODULE_NAME=udelay_test
+UDELAY_PATH=/sys/kernel/debug/udelay_test
+
+setup()
+{
+	/sbin/modprobe -q $MODULE_NAME
+	tmp_file=`mktemp`
+}
+
+test_one()
+{
+	delay=$1
+	echo $delay > $UDELAY_PATH
+	tee -a $tmp_file < $UDELAY_PATH
+}
+
+cleanup()
+{
+	if [ -f $tmp_file ]; then
+		rm $tmp_file
+	fi
+	/sbin/modprobe -q -r $MODULE_NAME
+}
+
+trap cleanup EXIT
+setup
+
+# Delay for a variety of times.
+# 1..200, 200..500 (by 10), 500..2000 (by 100)
+for (( delay = 1; delay < 200; delay += 1 )); do
+	test_one $delay
+done
+for (( delay = 200; delay < 500; delay += 10 )); do
+	test_one $delay
+done
+for (( delay = 500; delay <= 2000; delay += 100 )); do
+	test_one $delay
+done
+
+# Search for failures
+count=`grep -c FAIL $tmp_file`
+if [ $? -eq "0" ]; then
+	echo "ERROR: $count delays failed to delay long enough"
+	retcode=1
+fi
+
+exit $retcode