From 8994877c8c0d2cab6e5c7e8cf98df5ff580d87a8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Luk=C3=A1=C5=A1=20Nykr=C3=BDn?= <lnykryn@redhat.com>
Date: Tue, 14 Jun 2016 14:20:56 +0200
Subject: [PATCH] manager: reduce complexity of unit_gc_sweep (#3507)

When unit is marked as UNSURE, we are trying to find if it state was
changed over and over again. So lets not go through the UNSURE states
again. Also when we find a GOOD unit lets propagate the GOOD state to
all units that this unit reference.

This is a problem on machines with a lot of initscripts with different
starting priority, since those units will reference each other and the
original algorithm might get to n! complexity.

Thanks HATAYAMA Daisuke for the expand_good_state code.
Cherry-picked from: 4892084f096c19da0e83f28f250ca187b58c22b2
Resolves: #1344556
---
 src/core/manager.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/core/manager.c b/src/core/manager.c
index 7483a96..45ca540 100644
--- a/src/core/manager.c
+++ b/src/core/manager.c
@@ -765,6 +765,19 @@ enum {
         _GC_OFFSET_MAX
 };
 
+static void unit_gc_mark_good(Unit *u, unsigned gc_marker)
+{
+        Iterator i;
+        Unit *other;
+
+        u->gc_marker = gc_marker + GC_OFFSET_GOOD;
+
+        /* Recursively mark referenced units as GOOD as well */
+        SET_FOREACH(other, u->dependencies[UNIT_REFERENCES], i)
+                if (other->gc_marker == gc_marker + GC_OFFSET_UNSURE)
+                        unit_gc_mark_good(other, gc_marker);
+}
+
 static void unit_gc_sweep(Unit *u, unsigned gc_marker) {
         Iterator i;
         Unit *other;
@@ -774,6 +787,7 @@ static void unit_gc_sweep(Unit *u, unsigned gc_marker) {
 
         if (u->gc_marker == gc_marker + GC_OFFSET_GOOD ||
             u->gc_marker == gc_marker + GC_OFFSET_BAD ||
+            u->gc_marker == gc_marker + GC_OFFSET_UNSURE ||
             u->gc_marker == gc_marker + GC_OFFSET_IN_PATH)
                 return;
 
@@ -814,7 +828,7 @@ bad:
         return;
 
 good:
-        u->gc_marker = gc_marker + GC_OFFSET_GOOD;
+        unit_gc_mark_good(u, gc_marker);
 }
 
 static unsigned manager_dispatch_gc_queue(Manager *m) {