From 47ab8f73e3468b6e5a48218eacdb830e978d2cfd Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Fri, 11 Sep 2020 19:57:09 +0200
Subject: [PATCH] core: propagate unit start limit hit state to triggering path
 unit

We already do this for socket and automount units, do it for path units
too: if the triggered service keeps hitting the start limit, then fail
the triggering unit too, so that we don#t busy loop forever.

(Note that this leaves only timer units out in the cold for this kind of
protection, but it shouldn't matter there, as they are naturally
protected against busy loops: they are scheduled by time anyway).

Fixes: #16669
---
 src/core/path.c | 15 +++++++++++++++
 src/core/path.h |  1 +
 2 files changed, 16 insertions(+)

diff --git a/src/core/path.c b/src/core/path.c
index 8ffec72ede..4f4e7100cf 100644
--- a/src/core/path.c
+++ b/src/core/path.c
@@ -753,6 +753,20 @@ static void path_trigger_notify(Unit *u, Unit *other) {
         /* Filter out invocations with bogus state */
         assert(UNIT_IS_LOAD_COMPLETE(other->load_state));
 
+        /* Don't propagate state changes from the triggered unit if we are already down */
+        if (!IN_SET(p->state, PATH_WAITING, PATH_RUNNING))
+                return;
+
+        /* Propagate start limit hit state */
+        if (other->start_limit_hit) {
+                path_enter_dead(p, PATH_FAILURE_UNIT_START_LIMIT_HIT);
+                return;
+        }
+
+        /* Don't propagate anything if there's still a job queued */
+        if (other->job)
+                return;
+
         if (p->state == PATH_RUNNING &&
             UNIT_IS_INACTIVE_OR_FAILED(unit_active_state(other))) {
                 log_unit_debug(UNIT(p), "Got notified about unit deactivation.");
@@ -789,6 +803,7 @@ static const char* const path_result_table[_PATH_RESULT_MAX] = {
         [PATH_SUCCESS] = "success",
         [PATH_FAILURE_RESOURCES] = "resources",
         [PATH_FAILURE_START_LIMIT_HIT] = "start-limit-hit",
+        [PATH_FAILURE_UNIT_START_LIMIT_HIT] = "unit-start-limit-hit",
 };
 
 DEFINE_STRING_TABLE_LOOKUP(path_result, PathResult);
diff --git a/src/core/path.h b/src/core/path.h
index 9e2836535a..4043650fe0 100644
--- a/src/core/path.h
+++ b/src/core/path.h
@@ -45,6 +45,7 @@ typedef enum PathResult {
         PATH_SUCCESS,
         PATH_FAILURE_RESOURCES,
         PATH_FAILURE_START_LIMIT_HIT,
+        PATH_FAILURE_UNIT_START_LIMIT_HIT,
         _PATH_RESULT_MAX,
         _PATH_RESULT_INVALID = -1
 } PathResult;