[PATCH libevl v2] evl-test: add stress command support for background load testing

Add the ability to run a stress command (e.g. stress-ng) in the
background during test execution via the new -s option. This allows
testing EVL functionality under system load.

The stress command runs in its own process group (via setsid) to ensure
clean termination of all child processes, and is automatically stopped
when tests complete or the script exits normally or via signals.

The stress command output is redirected to /dev/null by default but can
be send to a file using the "EVL_TEST_STRESS_OUTPUT" environment
variable.

Usage example:
  evl-test -s "stress-ng --vm 2 --vm-bytes 1G --cpu 4" -k

Signed-off-by: Tobias Schaffner <[email protected]>
---
 utils/evl-test | 30 +++++++++++++++++++++++++++++-
 1 file changed, 29 insertions(+), 1 deletion(-)

diff --git a/utils/evl-test b/utils/evl-test
index 6e1edc3..28f2aed 100644
--- a/utils/evl-test
+++ b/utils/evl-test
@@ -7,7 +7,7 @@ if test \! -d $EVL_TESTDIR; then
 fi
 
 usage() {
-   echo >&2 "usage: $(basename $1) [-l][-L][-k][-r][-h] [test-list]"
+   echo >&2 "usage: $(basename $1) [-l][-L][-k][-r][-h][-s] [test-list]"
 }
 
 help=false
@@ -18,6 +18,8 @@ full_path=false
 test_args=false
 test_arg_list=
 test_list=
+stress_cmd=
+stress_pid=
 
 while test $# -gt 0
 do
@@ -37,6 +39,8 @@ do
 	    -L) full_path=true;
 		do_list=true;
 		shift;;
+	    -s) stress_cmd="$2";
+		shift 2;;
 	    --) test_args=true
 		shift;;
 	    -@) echo "run the EVL tests"
@@ -49,6 +53,28 @@ do
     fi
 done
 
+stop_stress() {
+    trap - EXIT INT TERM
+    if test -n "$stress_pid"; then
+        kill -TERM -$stress_pid 2>/dev/null
+        # Give the process up to one second to terminate gracefully
+        for i in $(seq 10); do kill -0 -$stress_pid 2>/dev/null || break; sleep 0.1; done
+        kill -KILL -$stress_pid 2>/dev/null
+        wait $stress_pid 2>/dev/null
+    fi
+    exit
+}
+
+start_stress() {
+    if test -n "$stress_cmd"; then
+        trap 'stop_stress' EXIT INT TERM
+        stress_output="${EVL_TEST_STRESS_OUTPUT:-/dev/null}"
+        setsid $stress_cmd </dev/null >"$stress_output" 2>&1 &
+        stress_pid=$!
+        sleep 1 # Give stress command time to start
+    fi
+}
+
 if test x$help = xtrue; then
    usage $0
    exit 0
@@ -73,6 +99,8 @@ if test x$do_list = xtrue; then
    exit 0
 fi
 
+start_stress
+
 result=0
 
 while : ; do
-- 
2.43.0