scx: Add infeasible weights test

Signed-off-by: David Vernet <[email protected]>

tools/testing/selftests/scx/infeasible.sh

@@ -0,0 +1,135 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2024 David Vernet <[email protected]>
+# Copyright (C) 2024 Meta Platforms, Inc. and affiliates.
+
+# Script to make a cgroup with conditions that should cause the infeasible
+# weight problem to manifest
+
+INFEASIBLE_CGRP="/sys/fs/cgroup/infeasible.scope"
+MINIMAL_CGRP="/sys/fs/cgroup/minimal.scope"
+
+# create_cgrp(grp) - Create a child of the root cgroup, and set its weight
+#	grp - The cgroup to create
+function create_cgrp() {
+	local cgrp="$1"
+	local weight=10000
+	if [[ ${cgrp} == ${MINIMAL_CGRP} ]]; then
+		weight=1
+	fi
+
+	if [[ ! -d "${cgrp}" ]]; then
+		mkdir "${cgrp}"
+		echo "created cgroup ${cgrp}"
+	else
+		echo "cgroup ${cgrp} already existed"
+		local curr_pids=$(cat "${cgrp}/pids.current")
+		if  [ "${curr_pids}" != "0" ]; then
+			echo "ERR: tasks found in ${cgrp}"
+			exit 1
+		fi
+	fi
+
+	echo "setting ${cgrp} weight to ${weight}"
+	echo ${weight} > "${cgrp}/cpu.weight"
+	echo "set ${cgrp} weight to ${weight}"
+}
+
+# invoke_stressng(ncpus) - Invoke the stress-ng utility with the specified # of CPUs
+#	ncpus - The number of CPU hogs to have spawned
+function invoke_stressng() {
+	local cpus=$1
+	stress-ng -c ${cpus} --cpu-load 100 --cpu-method matrixprod > /tmp/stressng_${cpus}.out 2> /tmp/stressng_${cpus}.out &
+	stressng_pid=$!
+	echo "stress-ng pid is ${stressng_pid}"
+	if [ ${stressng_pid} -le 0 ]; then
+		echo "ERR: failed to invoke stress-ng"
+		exit 1
+	fi
+}
+
+# move_into_cgrp(cgrp, pid) - Move @pid into the cgroup @cgrp
+#	cgrp - The cgrp to be moved into
+#	pid  - The pid of the process being moved
+function move_into_cgrp() {
+	local cgrp=$1
+	local pid=$2
+
+	local procsfile="${cgrp}/cgroup.procs"
+	local pidsfile="${cgrp}/pids.current"
+
+	echo "moving ${pid} into ${procsfile}"
+	echo "	procs in before: $(cat ${pidsfile})"
+	echo "${pid}" >> "${procsfile}"
+	local status=$?
+	echo "status was: ${status}"
+	if [ ${status} -ne 0 ]; then
+		echo "ERR: failed to move ${pid} into ${procsfile}"
+		echo "ERR: destroying ${pid}"
+		kill -9 ${pid}
+		echo "ERR: killed ${pid}. waiting for exit..."
+		wait
+		echo "ERR: ${pid} exited"
+		exit 1
+	fi
+	echo "	procs in after: $(cat ${pidsfile})"
+}
+
+# cleanup - Clean up after the script has run
+function cleanup() {
+	# Nothing to clean up, really. Just do some sanity checking at the end.
+	local curr_pids=$(cat "${INFEASIBLE_CGRP}/pids.current")
+	if  [ "${curr_pids}" != "0" ]; then
+		echo "WARN: ${curr_pids} tasks remaining in  ${INFEASIBLE_CGRP}"
+	fi
+
+	curr_pids=$(cat "${MINIMAL_CGRP}/pids.current")
+	if  [ "${curr_pids}" != "0" ]; then
+		echo "WARN: ${curr_pids} tasks remaining in  ${MINIMAL_CGRP}"
+	fi
+}
+
+# _term - Catch SIGINT and forward to the children so we can exit the script
+# cleanly.
+function _term() {
+	echo "Caught SIGINT signal"
+	kill -s SIGINT "${infeas_pid}"
+	kill -s SIGINT "${feas_pid}"
+}
+
+# Create the infeasible and minimal cgroups
+create_cgrp "${INFEASIBLE_CGRP}"
+create_cgrp "${MINIMAL_CGRP}"
+
+# The pids of the stress-ng processes we'll create
+infeas_pid=""
+feas_pid=""
+stressng_pid=""
+
+# Forward sigint so we can exit the script
+trap _term SIGINT
+
+# Move the script into a cgroup before spawning children. The children are
+# placed into whatever cgroup the parent is in, so this avoids any possible
+# races with stress-ng fork() / exec()'ing children after we move stress-ng
+# itself.
+
+# First the infeasible group
+move_into_cgrp "${INFEASIBLE_CGRP}" "$$"
+invoke_stressng 2
+infeas_pid=${stressng_pid}
+
+# Then feasible
+move_into_cgrp "${INFEASIBLE_CGRP}" "${infeas_pid}"
+move_into_cgrp "${MINIMAL_CGRP}" "$$"
+invoke_stressng $(nproc)
+feas_pid=${stressng_pid}
+move_into_cgrp "${MINIMAL_CGRP}" "${feas_pid}"
+
+# Done spawning + moving around. Let's let things run until we send a SIGINT
+echo "success"
+wait ${infeas_pid}
+echo "${infeas_pid} exited"
+wait ${feas_pid}
+echo "${feas_pid} exited"
+cleanup