File libvirt-Fix-potential-deadlock-when-agent-is-closed.patch of Package libvirt

From c5254d642359564859afe766d3ac522123de92e6 Mon Sep 17 00:00:00 2001
Message-Id: <c5254d642359564859afe766d3ac522123de92e6.1350297260.git.jdenemar@redhat.com>
From: "Daniel P. Berrange" <berrange@redhat.com>
Date: Wed, 10 Oct 2012 15:38:44 +0100
Subject: [PATCH] Fix potential deadlock when agent is closed

https://bugzilla.redhat.com/show_bug.cgi?id=859712

If the qemuAgentClose method is called from a place which holds
the domain lock, it is theoretically possible to get a deadlock
in the agent destroy callback. This has not been observed, but
the equivalent code in the QEMU monitor destroy callback has seen
a deadlock.

Remove the redundant locking while unrefing the object and the
bogus assignment

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
(cherry picked from commit 362d04779ce925725125a4eaa660c89d7313725f)
---
 src/qemu/qemu_process.c | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
index 429ba8f..127906e 100644
--- a/src/qemu/qemu_process.c
+++ b/src/qemu/qemu_process.c
@@ -128,7 +128,8 @@ qemuProcessHandleAgentEOF(qemuAgentPtr agent,
     virDomainObjLock(vm);
 
     priv = vm->privateData;
-    priv->agent = NULL;
+    if (priv->agent == agent)
+        priv->agent = NULL;
 
     virDomainObjUnlock(vm);
     qemuDriverUnlock(driver);
@@ -166,16 +167,9 @@ qemuProcessHandleAgentError(qemuAgentPtr agent ATTRIBUTE_UNUSED,
 static void qemuProcessHandleAgentDestroy(qemuAgentPtr agent,
                                           virDomainObjPtr vm)
 {
-    qemuDomainObjPrivatePtr priv;
-
     VIR_DEBUG("Received destroy agent=%p vm=%p", agent, vm);
 
-    virDomainObjLock(vm);
-    priv = vm->privateData;
-    if (priv->agent == agent)
-        priv->agent = NULL;
-    if (virObjectUnref(vm))
-        virDomainObjUnlock(vm);
+    virObjectUnref(vm);
 }
 
 
-- 
1.7.12.3