From 8c81776212d0aa44f5ae20635079bd6ce76d16ac Mon Sep 17 00:00:00 2001
From: Daan De Meyer <daan.j.demeyer@gmail.com>
Date: Tue, 19 Oct 2021 10:45:48 +0100
Subject: [PATCH] core: Delay start rate limit check when starting a unit

Doing start rate limit checks before doing condition checks made
condition check failures count towards the start rate limit which
broke existing assumptions (see #21025). Run the rate limit checks
after the condition checks again to restore the previous behaviour.

(cherry picked from commit ce2146f5256659c7fb53a7d5b9dc551252e27e7e)

Related: #2065322
---
 src/core/unit.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/src/core/unit.c b/src/core/unit.c
index 4fd9af87b7..b825e2418c 100644
--- a/src/core/unit.c
+++ b/src/core/unit.c
@@ -1729,13 +1729,6 @@ int unit_start(Unit *u) {
 
         assert(u);
 
-        /* Check our ability to start early so that failure conditions don't cause us to enter a busy loop. */
-        if (UNIT_VTABLE(u)->can_start) {
-                r = UNIT_VTABLE(u)->can_start(u);
-                if (r < 0)
-                        return r;
-        }
-
         /* If this is already started, then this will succeed. Note that this will even succeed if this unit
          * is not startable by the user. This is relied on to detect when we need to wait for units and when
          * waiting is finished. */
@@ -1790,6 +1783,13 @@ int unit_start(Unit *u) {
                 return unit_start(following);
         }
 
+        /* Check start rate limiting early so that failure conditions don't cause us to enter a busy loop. */
+        if (UNIT_VTABLE(u)->can_start) {
+                r = UNIT_VTABLE(u)->can_start(u);
+                if (r < 0)
+                        return r;
+        }
+
         /* If it is stopped, but we cannot start it, then fail */
         if (!UNIT_VTABLE(u)->start)
                 return -EBADR;