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

[Petr Vorel <pvorel@suse.cz>]

Hi Andrea,

> 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).

> 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
> +}
> +

If the test always TPASS or TCONF, please add it to lib/newlib_tests/runtest.sh
(to be run in CI).

...

> +. 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
So, we want to hide "write error: Permission denied"?

> +}
> +
> +_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
> +
> +	(
Interesting idea. Hopefully it could work (I'm not sure if tst_test.sh API will
work well with yet another subshell, if killing will work correctly).

> +		_tst_disable_oom_protection
> +		_TST_OOM_PROTECTION=0
> +		export _TST_OOM_PROTECTION
NOTE: you can export variable with value in a single command:
export _TST_OOM_PROTECTION=0

Also, "$_TST_" does not have the protection about misuse which "$TST_" has (that
protection for _tst_i in $(grep ... you modified).
Please use a different name with "$TST_". But best would be just to assign a
different value:
export TST_OOM_PROTECTION=2

> +		tst_run "$@"
Running the test in the cleanup phase, that looks to me strange.

> +	) &
> +	_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
And here have just:
	if [ "$TST_OOM_PROTECTION" = 1 ]; then

Kind regards,
Petr

> +		_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);;

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