From f195bfd717a92944c41935977b18c63d87937655 Mon Sep 17 00:00:00 2001
From: Michal Schmidt <mschmidt@redhat.com>
Date: Sun, 22 Apr 2012 02:09:04 +0200
Subject: [PATCH] transaction: fix detection of cycles involving installed
 jobs

A transaction can be acyclic, but when it's added to installed jobs,
a cycle may result.

transaction_verify_order_one() attempts to detect these cases, but it
fails because the installed jobs often have the exact generation number
that makes them look as if they were walked already.

Fix it by resetting the generation numbers of all installed jobs before
detecting cycles.

An alternative fix could be to add the generation counter to the
Manager and use it instead of starting always from 1 in
transaction_activate(). But I prefer not having to worry about it
wrapping around.
(cherry picked from commit 4e7bd268ae1f39675988b9ac61b9378a67e3ae3e)
---
 src/core/transaction.c |    8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/core/transaction.c b/src/core/transaction.c
index 3984947..394c181 100644
--- a/src/core/transaction.c
+++ b/src/core/transaction.c
@@ -603,6 +603,8 @@ rollback:
 }
 
 int transaction_activate(Transaction *tr, Manager *m, JobMode mode, DBusError *e) {
+        Iterator i;
+        Job *j;
         int r;
         unsigned generation = 1;
 
@@ -611,6 +613,12 @@ int transaction_activate(Transaction *tr, Manager *m, JobMode mode, DBusError *e
         /* This applies the changes recorded in tr->jobs to
          * the actual list of jobs, if possible. */
 
+        /* Reset the generation counter of all installed jobs. The detection of cycles
+         * looks at installed jobs. If they had a non-zero generation from some previous
+         * walk of the graph, the algorithm would break. */
+        HASHMAP_FOREACH(j, m->jobs, i)
+                j->generation = 0;
+
         /* First step: figure out which jobs matter */
         transaction_find_jobs_that_matter_to_anchor(tr->anchor_job, generation++);