[libvirt] udevadm settle can take too long

[Guido Günther]

Hi,
On Sun, Apr 22, 2012 at 02:41:54PM -0400, Jim Paris wrote:
> Hi,
> 
> http://bugs.debian.org/663931 is a bug I'm hitting, where virt-manager
> times out on the initial connection to libvirt.

I reassigned the bug back to libvirt. I still wonder what triggers this
though for some users but not for others?
Cheers,
 -- Guido

> 
> The basic problem is that, while checking storage volumes,
> virt-manager causes libvirt to call "udevadm settle".  There's an
> interaction where libvirt's earlier use of network namespaces (to probe
> LXC features) had caused some uevents to be sent that get filtered out
> before they reach udev.  This confuses "udevadm settle" a bit, and so
> it sits there waiting for a 2-3 minute built-in timeout before returning.
> Eventually libvirtd prints:
>   2012-04-22 18:22:18.678+0000: 30503: warning : virKeepAliveTimer:182 : No response from client 0x7feec4003630 after 5 keepalive messages in 30 seconds
> and virt-manager prints:
>   2012-04-22 18:22:18.931+0000: 30647: warning : virKeepAliveSend:128 : Failed to send keepalive response to client 0x25004e0
> and the connection gets dropped.
> 
> One workaround could be to specify a shorter timeout when doing the
> settle.  The patch appended below allows virt-manager to work,
> although the connection still has to wait for the 10 second timeout
> before it succeeds.  I don't know what a better solution would be,
> though.  It seems the udevadm behavior might not be considered a bug
> from the udev/kernel point of view:
>   https://lkml.org/lkml/2012/4/22/60
> 
> I'm using Linux 3.2.14 with libvirt 0.9.11.  You can trigger the
> udevadm issue using a program I posted at the Debian bug report link
> above.
> 
> -jim
> 
> >From 17e5b9ebab76acb0d711e8bc308023372fbc4180 Mon Sep 17 00:00:00 2001
> From: Jim Paris <jim at jtan.com>
> Date: Sun, 22 Apr 2012 14:35:47 -0400
> Subject: [PATCH] shorten udevadmin settle timeout
> 
> Otherwise, udevadmin settle can take so long that connections from
> e.g. virt-manager will get closed.
> ---
>  src/util/util.c |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/src/util/util.c b/src/util/util.c
> index 6e041d6..dfe458e 100644
> --- a/src/util/util.c
> +++ b/src/util/util.c
> @@ -2593,9 +2593,9 @@ virFileFindMountPoint(const char *type ATTRIBUTE_UNUSED)
>  void virFileWaitForDevices(void)
>  {
>  # ifdef UDEVADM
> -    const char *const settleprog[] = { UDEVADM, "settle", NULL };
> +    const char *const settleprog[] = { UDEVADM, "settle", "--timeout", "10", NULL };
>  # else
> -    const char *const settleprog[] = { UDEVSETTLE, NULL };
> +    const char *const settleprog[] = { UDEVSETTLE, "--timeout", "10", NULL };
>  # endif
>      int exitstatus;
>  
> -- 
> 1.7.7
> 
> 
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