core: coldplug possible nop_job

When a unit in a state INACTIVE or DEACTIVATING, JobType JOB_TRY_RESTART or
JOB_TRY_RELOAD will be collapsed to JOB_NOP. And use u->nop_job instead
of u->job.

If a JOB_NOP job is going on with a waiting state, a parallel daemon-reload
just install it during deserialization. Without a coldplug, the job will
not be in m->run_queue, which results in a hung try-restart or
try-reload process.

Reproduce:

    run systemctl try-restart test.servcie (inactive) repeatly in a terminal.
    run systemctl daemon-reload repeatly in other terminals.

After successful reproduce, systemctl list-jobs will list the hang job.

Upsteam:
systemd/systemd#13124

(cherry picked from commit b49e14d5f3081dfcd363d8199a14c0924ae9152f)

Resolves: #1829798

1 files changed, 4 insertions, 2 deletions

diff --git a/src/core/unit.c b/src/core/unit.c
index 61799bf9e3..f57260727f 100644
--- a/src/core/unit.c
+++ b/src/core/unit.c
@@ -3696,6 +3696,7 @@ int unit_add_node_dependency(Unit *u, const char *what, bool wants, UnitDependen
 int unit_coldplug(Unit *u) {
         int r = 0, q;
         char **i;
+        Job *uj;
 
         assert(u);
 
@@ -3718,8 +3719,9 @@ int unit_coldplug(Unit *u) {
                         r = q;
         }
 
-        if (u->job) {
-                q = job_coldplug(u->job);
+        uj = u->job ?: u->nop_job;
+        if (uj) {
+                q = job_coldplug(uj);
                 if (q < 0 && r >= 0)
                         r = q;
         }