From 289eb5ccd9c417533694fbd0f6ad8f3fa3bf8b9b Mon Sep 17 00:00:00 2001
From: Daniel De Graaf <code@danieldg.net>
Date: Wed, 26 Mar 2025 19:54:46 -0400
Subject: [PATCH] Wait for the cgroup request job to complete
The StartTransientUnit call returns as soon as the job is enqueued, but
does not wait for systemd to actually do the work. Wait for the job
completion signal before continuing to exec, or until 1 second has
passed.
---
compat/systemd.c | 90 ++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 90 insertions(+)
diff --git a/compat/systemd.c b/compat/systemd.c
index b3d51b81..15f33aad 100644
--- a/compat/systemd.c
+++ b/compat/systemd.c
@@ -75,16 +75,53 @@ fail:
return (-1);
}
+struct job_watch {
+ const char* path;
+ int done;
+};
+
+static int
+job_removed_handler(sd_bus_message *m, void *userdata, sd_bus_error *ret_error)
+{
+ struct job_watch *watch = userdata;
+ const char* path = NULL;
+ uint32_t id;
+ int r;
+ (void)ret_error;
+
+ /* This handler could be called during sd_bus_call. */
+ if (watch->path == NULL) {
+ return 0;
+ }
+
+ r = sd_bus_message_read(m, "uo", &id, &path);
+ if (r < 0) {
+ return (r);
+ }
+
+ if (strcmp(path, watch->path) == 0) {
+ watch->done = 1;
+ }
+
+ return (0);
+}
+
int
systemd_move_to_new_cgroup(char **cause)
{
sd_bus_error error = SD_BUS_ERROR_NULL;
sd_bus_message *m = NULL, *reply = NULL;
sd_bus *bus = NULL;
+ sd_bus_slot *slot = NULL;
char *name, *desc, *slice;
sd_id128_t uuid;
int r;
+ uint64_t elapsed_usec;
pid_t pid, parent_pid;
+ struct job_watch watch = {};
+ struct timeval start, now;
+
+ gettimeofday(&start, NULL);
/* Connect to the session bus. */
r = sd_bus_default_user(&bus);
@@ -94,6 +131,20 @@ systemd_move_to_new_cgroup(char **cause)
goto finish;
}
+ /* Start watching for JobRemoved events */
+ r = sd_bus_match_signal(bus, &slot,
+ "org.freedesktop.systemd1",
+ "/org/freedesktop/systemd1",
+ "org.freedesktop.systemd1.Manager",
+ "JobRemoved",
+ job_removed_handler,
+ &watch);
+ if (r < 0) {
+ xasprintf(cause, "failed to create match signal: %s",
+ strerror(-r));
+ goto finish;
+ }
+
/* Start building the method call. */
r = sd_bus_message_new_method_call(bus, &m,
"org.freedesktop.systemd1",
@@ -224,10 +275,49 @@ systemd_move_to_new_cgroup(char **cause)
goto finish;
}
+ /* Get the job (object path) from the reply */
+ r = sd_bus_message_read(reply, "o", &watch.path);
+ if (r < 0) {
+ xasprintf(cause, "failed to parse method reply: %s",
+ strerror(-r));
+ goto finish;
+ }
+
+ while (!watch.done) {
+ /* Process events, invoking callbacks that may set watch.done */
+ r = sd_bus_process(bus, NULL);
+ if (r < 0) {
+ xasprintf(cause, "failed waiting for cgroup allocation: %s",
+ strerror(-r));
+ goto finish;
+ }
+
+ /* A zero return means we should wait for events */
+ if (r != 0) {
+ continue;
+ }
+
+ gettimeofday(&now, NULL);
+ elapsed_usec = (now.tv_sec - start.tv_sec) * 1000000 + now.tv_usec - start.tv_usec;
+
+ if (elapsed_usec >= 1000000) {
+ xasprintf(cause, "timeout waiting for cgroup allocation");
+ goto finish;
+ }
+
+ r = sd_bus_wait(bus, 1000000 - elapsed_usec);
+ if (r < 0) {
+ xasprintf(cause, "failed waiting for cgroup allocation: %s",
+ strerror(-r));
+ goto finish;
+ }
+ }
+
finish:
sd_bus_error_free(&error);
sd_bus_message_unref(m);
sd_bus_message_unref(reply);
+ sd_bus_slot_unref(slot);
sd_bus_unref(bus);
return (r);