[libvirt] [PATCH] qemu: Fix a possible deadlock in p2p migration

[Jiri Denemark]

Two more calls to remote libvirtd have to be surrounded by
qemuDomainObjEnterRemoteWithDriver() and
qemuDomainObjExitRemoteWithDriver() to prevent possible deadlock between
two communicating libvirt daemons.

See commit f0c8e1cb3774d6f09e2681ca1988bf235a343007 for further details.
---
 src/qemu/qemu_driver.c |   18 ++++++++++++++++--
 1 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 54e9dcb..bc506c2 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -11622,24 +11622,38 @@ static int doPeer2PeerMigrate(virDomainPtr dom,
     int ret = -1;
     virConnectPtr dconn = NULL;
     char *dom_xml;
+    bool p2p;
 
     /* the order of operations is important here; we make sure the
      * destination side is completely setup before we touch the source
      */
 
+    qemuDomainObjEnterRemoteWithDriver(driver, vm);
     dconn = virConnectOpen(uri);
+    qemuDomainObjExitRemoteWithDriver(driver, vm);
     if (dconn == NULL) {
         qemuReportError(VIR_ERR_OPERATION_FAILED,
                         _("Failed to connect to remote libvirt URI %s"), uri);
         return -1;
     }
-    if (!VIR_DRV_SUPPORTS_FEATURE(dconn->driver, dconn,
-                                  VIR_DRV_FEATURE_MIGRATION_P2P)) {
+
+    qemuDomainObjEnterRemoteWithDriver(driver, vm);
+    p2p = VIR_DRV_SUPPORTS_FEATURE(dconn->driver, dconn,
+                                   VIR_DRV_FEATURE_MIGRATION_P2P);
+    qemuDomainObjExitRemoteWithDriver(driver, vm);
+    if (!p2p) {
         qemuReportError(VIR_ERR_OPERATION_FAILED, "%s",
                         _("Destination libvirt does not support peer-to-peer migration protocol"));
         goto cleanup;
     }
 
+    /* domain may have been stopped while we were talking to remote daemon */
+    if (!virDomainObjIsActive(vm)) {
+        qemuReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                        _("guest unexpectedly quit"));
+        goto cleanup;
+    }
+
     dom_xml = qemudVMDumpXML(driver, vm,
                              VIR_DOMAIN_XML_SECURE |
                              VIR_DOMAIN_XML_UPDATE_CPU);
-- 
1.7.3.2