[PATCH 3/5] nodedev: Don't join not spawned threads

[Michal Privoznik]

During the nodedev driver initialization two threads are created:
one for listening on udev events (like device plug/unplug) and
the other for enumerating devices (so that the main thread doing
the driver init is not blocked). If something goes wrong at any
point then nodeStateCleanup() is called which joins those two
threads (possibly) created before. But it tries to join them even
they weren't created which is undefined behaviour (and it just so
happens that it crashes on my system).

If those two virThread variables are turned into pointers then we
can use comparison against NULL to detect whether threads were
created.

Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
---
 src/node_device/node_device_udev.c | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/src/node_device/node_device_udev.c b/src/node_device/node_device_udev.c
index da3754ff80..3e9c7a8d80 100644
--- a/src/node_device/node_device_udev.c
+++ b/src/node_device/node_device_udev.c
@@ -63,13 +63,13 @@ struct _udevEventData {
     int watch;
 
     /* Thread data */
-    virThread th;
+    virThread *th;
     virCond threadCond;
     bool threadQuit;
     bool dataReady;
 
     /* init thread */
-    virThread initThread;
+    virThread *initThread;
 
     GList *mdevctlMonitors;
     virMutex mdevctlLock;
@@ -1685,8 +1685,14 @@ nodeStateCleanup(void)
         priv->threadQuit = true;
         virCondSignal(&priv->threadCond);
         virObjectUnlock(priv);
-        virThreadJoin(&priv->initThread);
-        virThreadJoin(&priv->th);
+        if (priv->initThread) {
+            virThreadJoin(priv->initThread);
+            g_clear_pointer(&priv->initThread, g_free);
+        }
+        if (priv->th) {
+            virThreadJoin(priv->th);
+            g_clear_pointer(&priv->th, g_free);
+        }
     }
 
     virObjectUnref(priv);
@@ -2243,10 +2249,12 @@ nodeStateInitialize(bool privileged,
         udev_monitor_set_receive_buffer_size(priv->udev_monitor,
                                              128 * 1024 * 1024);
 
-    if (virThreadCreateFull(&priv->th, true, udevEventHandleThread,
+    priv->th = g_new0(virThread, 1);
+    if (virThreadCreateFull(priv->th, true, udevEventHandleThread,
                             "udev-event", false, NULL) < 0) {
         virReportSystemError(errno, "%s",
                              _("failed to create udev handler thread"));
+        g_clear_pointer(&priv->th, g_free);
         goto unlock;
     }
 
@@ -2284,10 +2292,12 @@ nodeStateInitialize(bool privileged,
     if (udevSetupSystemDev() != 0)
         goto cleanup;
 
-    if (virThreadCreateFull(&priv->initThread, true, nodeStateInitializeEnumerate,
+    priv->initThread = g_new0(virThread, 1);
+    if (virThreadCreateFull(priv->initThread, true, nodeStateInitializeEnumerate,
                             "nodedev-init", false, udev) < 0) {
         virReportSystemError(errno, "%s",
                              _("failed to create udev enumerate thread"));
+        g_clear_pointer(&priv->initThread, g_free);
         goto cleanup;
     }
 
-- 
2.26.3