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

[Marc Hartmayer]

On Thu, Feb 07, 2019 at 05:08 PM +0100, Marc Hartmayer <mhartmay at linux.ibm.com> wrote:
> 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
>
> --
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Sorry… I forgot to add John to CC.

Kind regards / Beste Grüße
   Marc Hartmayer

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