Fix John GPU stress duration semantics

iso/overlay/usr/local/bin/bee-john-gpu-stress

@@ -1,10 +1,11 @@
 #!/bin/sh
 set -eu
 
-SECONDS=300
+DURATION_SEC=300
 DEVICES=""
 EXCLUDE=""
 FORMAT=""
+TEST_SLICE_SECONDS=300
 JOHN_DIR="/usr/local/lib/bee/john/run"
 JOHN_BIN="${JOHN_DIR}/john"
 export OCL_ICD_VENDORS="/etc/OpenCL/vendors"
@@ -116,7 +117,7 @@ ensure_opencl_ready() {
 
 while [ "$#" -gt 0 ]; do
     case "$1" in
-        --seconds|-t) [ "$#" -ge 2 ] || usage; SECONDS="$2"; shift 2 ;;
+        --seconds|-t) [ "$#" -ge 2 ] || usage; DURATION_SEC="$2"; shift 2 ;;
         --devices) [ "$#" -ge 2 ] || usage; DEVICES="$2"; shift 2 ;;
         --exclude) [ "$#" -ge 2 ] || usage; EXCLUDE="$2"; shift 2 ;;
         --format) [ "$#" -ge 2 ] || usage; FORMAT="$2"; shift 2 ;;
@@ -189,14 +190,51 @@ CHOSEN_FORMAT=$(choose_format) || {
     exit 1
 }
 
-echo "format=${CHOSEN_FORMAT}"
+run_john_loop() {
+    opencl_id="$1"
+    deadline="$2"
+    round=0
+    while :; do
+        now=$(date +%s)
+        remaining=$((deadline - now))
+        if [ "${remaining}" -le 0 ]; then
+            break
+        fi
+        round=$((round + 1))
+        slice="${remaining}"
+        if [ "${slice}" -gt "${TEST_SLICE_SECONDS}" ]; then
+            slice="${TEST_SLICE_SECONDS}"
+        fi
+        echo "device=${opencl_id} round=${round} remaining_sec=${remaining} slice_sec=${slice}"
+        ./john --test="${slice}" --format="${CHOSEN_FORMAT}" --devices="${opencl_id}" || return 1
+    done
+}
+
 PIDS=""
+cleanup() {
+    rc=$?
+    trap - EXIT INT TERM
+    for pid in ${PIDS}; do
+        kill "${pid}" 2>/dev/null || true
+    done
+    for pid in ${PIDS}; do
+        wait "${pid}" 2>/dev/null || true
+    done
+    exit "${rc}"
+}
+trap cleanup EXIT INT TERM
+
+echo "format=${CHOSEN_FORMAT}"
+echo "target_seconds=${DURATION_SEC}"
+echo "slice_seconds=${TEST_SLICE_SECONDS}"
+DEADLINE=$(( $(date +%s) + DURATION_SEC ))
 _first=1
 for opencl_id in $(echo "${JOHN_DEVICES}" | tr ',' ' '); do
     [ "${_first}" = "1" ] || sleep 3
     _first=0
-    ./john --test="${SECONDS}" --format="${CHOSEN_FORMAT}" --devices="${opencl_id}" &
+    run_john_loop "${opencl_id}" "${DEADLINE}" &
-    PIDS="${PIDS} $!"
+    pid=$!
+    PIDS="${PIDS} ${pid}"
 done
 FAIL=0
 for pid in ${PIDS}; do