[PATCH v2 1/2] shell: add optional OOM protection

From: Andrea Cervesato <andrea.cervesato-IBi9RG/[email protected]>

Add TST_OOM_PROTECTION to activate OOM protection in shell tests. When
enabled, the shell harness shields itself from the OOM killer and runs
the test in a child process, so it survives memory pressure and can
still report results (e.g. during memcg stress tests).

Signed-off-by: Andrea Cervesato <andrea.cervesato-IBi9RG/[email protected]>
---
 doc/developers/writing_tests.rst            |  3 ++
 testcases/lib/tests/shell_oom_protection.sh | 42 +++++++++++++++++++++
 testcases/lib/tst_test.sh                   | 57 ++++++++++++++++++++++++++++-
 3 files changed, 101 insertions(+), 1 deletion(-)

diff --git a/doc/developers/writing_tests.rst b/doc/developers/writing_tests.rst
index 4db57898fcf08b83e68be996f666e91c418838fc..2d5bc294083fa2b89212714f0a6c5e5c3f22777a 100644
--- a/doc/developers/writing_tests.rst
+++ b/doc/developers/writing_tests.rst
@@ -549,6 +549,9 @@ LTP C And Shell Test API Comparison
     * - not applicable
       - TST_FS_TYPE
 
+    * - not applicable
+      - TST_OOM_PROTECTION
+
 .. list-table::
     :header-rows: 1
 
diff --git a/testcases/lib/tests/shell_oom_protection.sh b/testcases/lib/tests/shell_oom_protection.sh
new file mode 100755
index 0000000000000000000000000000000000000000..aeab36816ee7d8eeae9366d2199a0aabde73e25a
--- /dev/null
+++ b/testcases/lib/tests/shell_oom_protection.sh
@@ -0,0 +1,42 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0-or-later
+# Copyright (c) 2026 Linux Test Project
+#
+# doc
+# Verify that TST_OOM_PROTECTION shields the shell harness from the OOM
+# killer and resets the test process oom_score_adj to 0.
+#
+# ---
+# env
+# {
+# }
+# ---
+
+TST_TESTFUNC=do_test
+TST_OOM_PROTECTION=1
+
+read_oom_score_adj() {
+	cat "/proc/$1/oom_score_adj" 2>/dev/null
+}
+
+do_test() {
+	local self_score harness_score
+
+	self_score=$(read_oom_score_adj self)
+	harness_score=$(read_oom_score_adj "$$")
+
+	if [ "$self_score" = 0 ]; then
+		tst_res TPASS "test process has oom_score_adj reset to 0"
+	else
+		tst_res TFAIL "test process oom_score_adj is $self_score, expected 0"
+	fi
+
+	if [ "$harness_score" = -1000 ]; then
+		tst_res TPASS "shell harness is protected from OOM"
+	else
+		tst_res TCONF "shell harness OOM protection unavailable"
+	fi
+}
+
+. tst_test.sh
+tst_run
diff --git a/testcases/lib/tst_test.sh b/testcases/lib/tst_test.sh
index 8701bb3903889b009f88ba98bac47534608cdd0a..48dacb432b953295ae4ad710e4f27ed87ac0a7e5 100644
--- a/testcases/lib/tst_test.sh
+++ b/testcases/lib/tst_test.sh
@@ -28,6 +28,57 @@ export TST_USR_GID="${LTP_USR_GID:-65534}"
 trap "tst_brk TBROK 'test interrupted'" INT
 trap "unset _tst_setup_timer_pid; tst_brk TBROK 'test terminated'" TERM
 
+_tst_set_oom_score_adj()
+{
+	local value="$1"
+	local path="/proc/self/oom_score_adj"
+
+	[ -e "$path" ] || return 0
+
+	echo "$value" > "$path" 2>/dev/null || return 0
+}
+
+_tst_enable_oom_protection()
+{
+	_tst_set_oom_score_adj -1000
+}
+
+_tst_disable_oom_protection()
+{
+	_tst_set_oom_score_adj 0
+}
+
+_tst_run_oom_protected()
+{
+	local _tst_pid
+	local _tst_ret
+
+	# Shield the harness from the OOM killer and run the test in a child.
+	# The child keeps the default oom_score_adj so that it, and any process
+	# it spawns, stay killable under memory pressure while the harness
+	# survives to report results.
+	_tst_enable_oom_protection
+
+	(
+		_tst_disable_oom_protection
+		_TST_OOM_PROTECTION=0
+		export _TST_OOM_PROTECTION
+		tst_run "$@"
+	) &
+	_tst_pid=$!
+
+	wait "$_tst_pid"
+	_tst_ret=$?
+
+	if [ "$_tst_ret" -eq 137 ]; then
+		tst_res TINFO "Test was SIGKILLed: OOM killer or timeout?"
+		tst_res TINFO "On a slow machine try exporting LTP_TIMEOUT_MUL > 1"
+		tst_brk TBROK "Test killed!"
+	fi
+
+	exit "$_tst_ret"
+}
+
 _tst_do_cleanup()
 {
 	if [ -n "$TST_DO_CLEANUP" -a -n "$TST_CLEANUP" -a -z "$LTP_NO_CLEANUP" ]; then
@@ -680,12 +731,16 @@ tst_run()
 	local _tst_pattern='[='\''"} \t\/:`$\;|].*'
 	local ret
 
+	if [ "$TST_OOM_PROTECTION" = 1 -a "$_TST_OOM_PROTECTION" != 0 ]; then
+		_tst_run_oom_protected "$@"
+	fi
+
 	if [ -n "$TST_TEST_PATH" ]; then
 		for _tst_i in $(grep '^[^#]*\<TST_' "$TST_TEST_PATH" | sed "s/.*TST_//; s/$_tst_pattern//"); do
 			case "$_tst_i" in
 			ALL_FILESYSTEMS|DISABLE_APPARMOR|DISABLE_SELINUX);;
 			SETUP|CLEANUP|TESTFUNC|ID|CNT|MIN_KVER);;
-			OPTS|USAGE|PARSE_ARGS|POS_ARGS);;
+			OPTS|USAGE|PARSE_ARGS|POS_ARGS|OOM_PROTECTION);;
 			NEEDS_ROOT|NEEDS_TMPDIR|TMPDIR|NEEDS_DEVICE|DEVICE);;
 			NEEDS_CMDS|NEEDS_MODULE|MODPATH|DATAROOT);;
 			NEEDS_DRIVERS|FS_TYPE|MNTPOINT|MNT_PARAMS);;

-- 
2.51.0


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