[libvirt] [PATCH] create a thread to handle MigrationParamReset to avoid deadlock

[Yi Wang]

From: Li XueLei <li.xuelei1 at zte.com.cn>

Libvirtd no longer receives external requests, after I do the following.

Steps to reproduce:
1.Virsh tool initiates a non-p2p migrations.
2.After the phase of qemuDomainMigratePerform3 and before the phase of
  qemuDomainMigrateConfirm3, kill the virsh client which initiated the
  migration.

What happens:
    Libvirtd will be blocked in the next call stack because it can't
get the condition variables, and it will not be able to receive new
requests.

Thread 1 (Thread 0x7f36a7b9f8c0 (LWP 27556)):
#0  0x00007f36a45799f5 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0
#1  0x00007f36a6e7a97e in virCondWait () from /lib64/libvirt.so.0
#2  0x00007f3679c6a1b3 in qemuMonitorSend () from /usr/lib64/libvirt/connection-driver/libvirt_driver_qemu.so
#3  0x00007f3679c837de in qemuMonitorJSONCommandWithFd () from /usr/lib64/libvirt/connection-driver/libvirt_driver_qemu.so
#4  0x00007f3679c93c5a in qemuMonitorJSONSetMigrationCapabilities () from /usr/lib64/libvirt/connection-driver/libvirt_driver_qemu.so
#5  0x00007f3679c786ed in qemuMonitorSetMigrationCapabilities () from /usr/lib64/libvirt/connection-driver/libvirt_driver_qemu.so
#6  0x00007f3679c67857 in qemuMigrationParamsApply () from /usr/lib64/libvirt/connection-driver/libvirt_driver_qemu.so
#7  0x00007f3679c67eff in qemuMigrationParamsReset () from /usr/lib64/libvirt/connection-driver/libvirt_driver_qemu.so
#8  0x00007f3679c5198a in qemuMigrationSrcCleanup () from /usr/lib64/libvirt/connection-driver/libvirt_driver_qemu.so
#9  0x00007f36a6dcd862 in virCloseCallbacksRun () from /lib64/libvirt.so.0
#10 0x00007f3679cc28f6 in qemuConnectClose () from /usr/lib64/libvirt/connection-driver/libvirt_driver_qemu.so
#11 0x00007f36a70a0870 in virConnectDispose () from /lib64/libvirt.so.0
#12 0x00007f36a6e3f43b in virObjectUnref () from /lib64/libvirt.so.0
#13 0x00007f36a70a55c4 in virConnectClose () from /lib64/libvirt.so.0
#14 0x000056058a206f92 in remoteClientFree ()
#15 0x00007f36a6fa49a0 in virNetServerClientDispose () from /lib64/libvirt.so.0
#16 0x00007f36a6e3f43b in virObjectUnref () from /lib64/libvirt.so.0
#17 0x00007f36a6e3fd21 in virObjectFreeCallback () from /lib64/libvirt.so.0
#18 0x00007f36a6f9942e in virNetSocketEventFree () from /lib64/libvirt.so.0
#19 0x00007f36a6de8439 in virEventPollCleanupHandles () from /lib64/libvirt.so.0
#20 0x00007f36a6de9ab6 in virEventPollRunOnce () from /lib64/libvirt.so.0
#21 0x00007f36a6de817a in virEventRunDefaultImpl () from /lib64/libvirt.so.0
#22 0x00007f36a6faadb5 in virNetDaemonRun () from /lib64/libvirt.so.0
#23 0x000056058a1c5cc1 in main ()

Here's a patch to solve this bug, that is to create a thread to do
MigrationParamReset.

Signed-off-by: Li XueLei <li.xuelei1 at zte.com.cn>
Signed-off-by: Yi Wang <wang.yi59 at zte.com.cn>

---
 src/remote/remote_daemon_dispatch.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/src/remote/remote_daemon_dispatch.c b/src/remote/remote_daemon_dispatch.c
index 76c676c..3962ee3 100644
--- a/src/remote/remote_daemon_dispatch.c
+++ b/src/remote/remote_daemon_dispatch.c
@@ -1741,9 +1741,10 @@ remoteClientFreePrivateCallbacks(struct daemonClientPrivate *priv)
  * We keep the libvirt connection open until any async
  * jobs have finished, then clean it up elsewhere
  */
-void remoteClientFree(void *data)
+
+static void remoteClientFreeFun(void *opaque)
 {
-    struct daemonClientPrivate *priv = data;
+    struct daemonClientPrivate *priv = opaque;
 
     if (priv->conn)
         virConnectClose(priv->conn);
@@ -1760,7 +1761,16 @@ void remoteClientFree(void *data)
     if (priv->storageConn)
         virConnectClose(priv->storageConn);
 
-    VIR_FREE(priv);
+    VIR_FREE(priv);
+}
+
+void remoteClientFree(void *data)
+{
+    virThread thread;
+
+    if (virThreadCreate(&thread, false, remoteClientFreeFun, data) < 0) {
+        VIR_ERROR("Unable to create remoteClientFreeFun thread");
+    }
 }
 
 
-- 
1.8.3.1