[libvirt] [RFC PATCH] udev: Remove udev handle from main loop when udev thread stops

[Marc Hartmayer]

Commit "nodedev: Move device enumumeration out of nodeStateInitialize"
(9f0ae0b18e3e620) has moved the heavy task of device enumeration into
a separate thread. The problem with this commit is that there is a
functionality change in the cleanup when udevEnumerateDevices
fails. Before commit 9f0ae0b18e3e620, the entire driver was cleaned up
by calling nodeStateCleanup (defined in node_device_udev.c) which
resulted in libvirtd stopping with the error message
'daemonRunStateInit:800 : Driver state initialization failed'. With
the commit 9f0ae0b18e3e620 there is only a signal to the udev thread
that it must stop. This means that for example the watch handle isn't
removed from the main loop and this can result in the main loop
consuming 100% CPU time as soon as a new udev event occurs.

This patch proposes a simple solution to the described problem. In
case the udev thread stops the watch handle is removed from the main
loop.

Fixes: 9f0ae0b18e3e620 ("nodedev: Move device enumumeration out of nodeStateInitialize")
Signed-off-by: Marc Hartmayer <mhartmay at linux.ibm.com>
---

Note: I'm not sure whether we should stop libvirtd (as it would have
      been done before) or if this patch is already sufficient.

---
 src/node_device/node_device_udev.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/node_device/node_device_udev.c b/src/node_device/node_device_udev.c
index b1e5f00067e8..299f55260129 100644
--- a/src/node_device/node_device_udev.c
+++ b/src/node_device/node_device_udev.c
@@ -1628,6 +1628,13 @@ udevEventHandleThread(void *opaque ATTRIBUTE_UNUSED)
         }
 
         if (priv->threadQuit) {
+            if (priv->watch != -1) {
+                /* Since the udev thread getting stopped remove the
+                 * watch handle from the main loop */
+                virEventRemoveHandle(priv->watch);
+                priv->watch = -1;
+            }
+
             virObjectUnlock(priv);
             return;
         }
-- 
2.17.0