[libvirt] [PATCH] Ensure driver lock is released when entering QEMU monitor

["Daniel P. Berrange" <berrange@xxxxxxxxxx>]

The qemudStartVMDaemon() and several functions it calls use
the QEMU monitor. The QEMU driver is locked while this function
is executing, so it is rquired to release the driver lock and
reacquire it either side of issuing a monitor command. It
failed todo so, leading to deadlock

* qemu/qemu_driver.c: Release driver when in qemudStartVMDaemon
  and things it calls
---
 src/qemu/qemu_driver.c |   29 ++++++++++++++++-------------
 1 files changed, 16 insertions(+), 13 deletions(-)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 968118e..a4a87ac 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -118,6 +118,7 @@ static void qemudShutdownVMDaemon(virConnectPtr conn,
 static int qemudDomainGetMaxVcpus(virDomainPtr dom);
 
 static int qemuDetectVcpuPIDs(virConnectPtr conn,
+                              struct qemud_driver *driver,
                               virDomainObjPtr vm);
 
 static int qemuUpdateActivePciHostdevs(struct qemud_driver *driver,
@@ -1314,6 +1315,7 @@ qemudWaitForMonitor(virConnectPtr conn,
 
 static int
 qemuDetectVcpuPIDs(virConnectPtr conn,
+                   struct qemud_driver *driver,
                    virDomainObjPtr vm) {
     pid_t *cpupids = NULL;
     int ncpupids;
@@ -1331,12 +1333,12 @@ qemuDetectVcpuPIDs(virConnectPtr conn,
 
     /* What follows is now all KVM specific */
 
-    qemuDomainObjEnterMonitor(vm);
+    qemuDomainObjEnterMonitorWithDriver(driver, vm);
     if ((ncpupids = qemuMonitorGetCPUInfo(priv->mon, &cpupids)) < 0) {
-        qemuDomainObjExitMonitor(vm);
+        qemuDomainObjExitMonitorWithDriver(driver, vm);
         return -1;
     }
-    qemuDomainObjExitMonitor(vm);
+    qemuDomainObjExitMonitorWithDriver(driver, vm);
 
     /* Treat failure to get VCPU<->PID mapping as non-fatal */
     if (ncpupids == 0)
@@ -1357,6 +1359,7 @@ qemuDetectVcpuPIDs(virConnectPtr conn,
 
 static int
 qemudInitCpus(virConnectPtr conn,
+              struct qemud_driver *driver,
               virDomainObjPtr vm,
               const char *migrateFrom) {
 #if HAVE_SCHED_GETAFFINITY
@@ -1397,15 +1400,15 @@ qemudInitCpus(virConnectPtr conn,
     /* XXX This resume doesn't really belong here. Move it up to caller */
     if (migrateFrom == NULL) {
         /* Allow the CPUS to start executing */
-        qemuDomainObjEnterMonitor(vm);
+        qemuDomainObjEnterMonitorWithDriver(driver, vm);
         if (qemuMonitorStartCPUs(priv->mon, conn) < 0) {
             if (virGetLastError() == NULL)
                 qemudReportError(conn, NULL, NULL, VIR_ERR_INTERNAL_ERROR,
                                  "%s", _("resume operation failed"));
-            qemuDomainObjExitMonitor(vm);
+            qemuDomainObjExitMonitorWithDriver(driver, vm);
             return -1;
         }
-        qemuDomainObjExitMonitor(vm);
+        qemuDomainObjExitMonitorWithDriver(driver, vm);
     }
 
     return 0;
@@ -1422,12 +1425,12 @@ qemuInitPasswords(struct qemud_driver *driver,
         vm->def->graphics[0]->type == VIR_DOMAIN_GRAPHICS_TYPE_VNC &&
         (vm->def->graphics[0]->data.vnc.passwd || driver->vncPassword)) {
 
-        qemuDomainObjEnterMonitor(vm);
+        qemuDomainObjEnterMonitorWithDriver(driver, vm);
         ret = qemuMonitorSetVNCPassword(priv->mon,
                                         vm->def->graphics[0]->data.vnc.passwd ?
                                         vm->def->graphics[0]->data.vnc.passwd :
                                         driver->vncPassword);
-        qemuDomainObjExitMonitor(vm);
+        qemuDomainObjExitMonitorWithDriver(driver, vm);
     }
 
     return ret;
@@ -2294,21 +2297,21 @@ static int qemudStartVMDaemon(virConnectPtr conn,
     if (qemudWaitForMonitor(conn, driver, vm, pos) < 0)
         goto abort;
 
-    if (qemuDetectVcpuPIDs(conn, vm) < 0)
+    if (qemuDetectVcpuPIDs(conn, driver, vm) < 0)
         goto abort;
 
-    if (qemudInitCpus(conn, vm, migrateFrom) < 0)
+    if (qemudInitCpus(conn, driver, vm, migrateFrom) < 0)
         goto abort;
 
     if (qemuInitPasswords(driver, vm) < 0)
         goto abort;
 
-    qemuDomainObjEnterMonitor(vm);
+    qemuDomainObjEnterMonitorWithDriver(driver, vm);
     if (qemuMonitorSetBalloon(priv->mon, vm->def->memory) < 0) {
-        qemuDomainObjExitMonitor(vm);
+        qemuDomainObjExitMonitorWithDriver(driver, vm);
         goto abort;
     }
-    qemuDomainObjExitMonitor(vm);
+    qemuDomainObjExitMonitorWithDriver(driver, vm);
 
     if (virDomainSaveStatus(conn, driver->stateDir, vm) < 0)
         goto abort;
-- 
1.6.5.2

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