udev: enable kill workers timer when processing events stopped (#37382)

This also extends test cases for
`udevadm control --start-exec-queue/--stop-exec-queue`.

src/udev/udev-manager-ctrl.c

@@ -29,6 +29,7 @@ static int on_ctrl_msg(UdevCtrl *uctrl, UdevCtrlMessageType type, const UdevCtrl
         case UDEV_CTRL_STOP_EXEC_QUEUE:
                 log_debug("Received udev control message (STOP_EXEC_QUEUE)");
                 manager->stop_exec_queue = true;
+                (void) manager_reset_kill_workers_timer(manager);
                 break;
         case UDEV_CTRL_START_EXEC_QUEUE:
                 log_debug("Received udev control message (START_EXEC_QUEUE)");

src/udev/udev-manager.c

@@ -201,7 +201,7 @@ static int on_kill_workers_event(sd_event_source *s, uint64_t usec, void *userda
         return 0;
 }
 
-static int manager_reset_kill_workers_timer(Manager *manager) {
+int manager_reset_kill_workers_timer(Manager *manager) {
         int r;
 
         assert(manager);

src/udev/udev-manager.h

@@ -93,6 +93,7 @@ void manager_exit(Manager *manager);
 void notify_ready(Manager *manager);
 
 void manager_kill_workers(Manager *manager, int signo);
+int manager_reset_kill_workers_timer(Manager *manager);
 
 bool devpath_conflict(const char *a, const char *b);
 

src/udev/udev-varlink.c

@@ -136,6 +136,14 @@ static int vl_method_start_stop_exec_queue(sd_varlink *link, sd_json_variant *pa
 
         log_debug("Received %s()", method);
         manager->stop_exec_queue = streq(method, "io.systemd.Udev.StopExecQueue");
+
+        /* In case that processing queued events will be stopped for a while, regardless if there exist
+         * queued events, enable the kill workers timer here unless it is already enabled. Note, it is not
+         * necessary to disable the timer when processing is restarted, as it will be anyway disabled in
+         * on_post() -> event_queue_start(). */
+        if (manager->stop_exec_queue)
+                (void) manager_reset_kill_workers_timer(manager);
+
         return sd_varlink_reply(link, NULL);
 }
 

test/units/TEST-17-UDEV.sanity-check.sh

@@ -9,7 +9,7 @@ set -o pipefail
 # Coverage test for udevadm
 
 # shellcheck disable=SC2317
-cleanup_17_10() {
+cleanup() {
     set +e
 
     losetup -d "$loopdev"
@@ -19,9 +19,9 @@ cleanup_17_10() {
 }
 
 # Set up some test devices
-trap cleanup_17_10 EXIT
+trap cleanup EXIT
 
-netdev=dummy17.10
+netdev=hoge
 ip link add $netdev type dummy
 
 blk="$(mktemp)"
@@ -55,8 +55,18 @@ udevadm control -l notice
 udevadm control --log-level info
 udevadm control --log-level debug
 (! udevadm control -l hello)
-udevadm control -s
-udevadm control -S
+
+# Check if processing queued events has been stopped.
+udevadm control --stop-exec-queue
+ip link add foobar type dummy
+(! udevadm info --wait-for-initialization=3 /sys/class/net/foobar)
+(! udevadm settle --timeout=0)
+# Check if processing queued events has been restarted.
+udevadm control --start-exec-queue
+udevadm settle --timeout=30
+udevadm info --wait-for-initialization=0 /sys/class/net/foobar
+ip link del foobar
+
 udevadm control -R
 udevadm control -p HELLO=world
 udevadm control -m 42