From b629c64e5e0a32ef439b8eeb3a697e2cd76f3248 Mon Sep 17 00:00:00 2001
From: Martin Kletzander <mkletzan@redhat.com>
Date: Nov 03 2014 15:43:23 +0000
Subject: qemu: avoid rare race when undefining domain


When one domain is being undefined and at the same time started, for
example, there is a possibility of a rare problem occuring.

 - Thread 1 does virDomainUndefine(), has the lock, checks that the
   domain is active and because it's not, calls
   virDomainObjListRemove().

 - Thread 2 does virDomainCreate() and tries to lock the domain.

 - Thread 1 needs to lock domain list in order to remove the domain from
   it, but must unlock domain first (proper order is to lock domain list
   first and the domain itself second).

 - Thread 2 grabs the lock, starts the domain and releases the lock.

 - Thread 1 grabs the lock and removes the domain from list.

With this patch:

 - qemuDomainRemoveInactive() creates a QEMU_JOB_MODIFY if that's
   possible, but since it must remove the domain from list either way,
   it continues even when starting the job failed.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1150505

Signed-off-by: Martin Kletzander <mkletzan@redhat.com>

---

diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index 76fccce..0caf1c0 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -2392,9 +2392,13 @@ void
 qemuDomainRemoveInactive(virQEMUDriverPtr driver,
                          virDomainObjPtr vm)
 {
+    bool haveJob = true;
     char *snapDir;
     virQEMUDriverConfigPtr cfg = virQEMUDriverGetConfig(driver);
 
+    if (qemuDomainObjBeginJob(driver, vm, QEMU_JOB_MODIFY) < 0)
+        haveJob = false;
+
     /* Remove any snapshot metadata prior to removing the domain */
     if (qemuDomainSnapshotDiscardAllMetadata(driver, vm) < 0) {
         VIR_WARN("unable to remove all snapshots for domain %s",
@@ -2411,6 +2415,9 @@ qemuDomainRemoveInactive(virQEMUDriverPtr driver,
     }
     virDomainObjListRemove(driver->domains, vm);
     virObjectUnref(cfg);
+
+    if (haveJob)
+        ignore_value(qemuDomainObjEndJob(driver, vm));
 }
 
 void