Re: hanging tapdisk2 processes and improper udev rules

[Ian Campbell <Ian.Campbell@citrix.com>]

On Fri, 2011-07-22 at 10:18 +0100, Andreas Olsowski wrote:
> When i xl-create a guest, i get one message per assigned block device:
> 
> root@xenturio1:/var/log# xl create /etc/xen/domains/x1test.sxp
> Parsing config file /etc/xen/domains/x1test.sxp
> Daemon running with PID 8704
> 
> root@xenturio1:/var/log# tail -10 error |grep SYMLINK
> syslog:Jul 22 10:58:05 xenturio1 udevd[8658]: kernel-provided name 
> 'blktap2' and NAME= 'xen/blktap-2/blktap2' disagree, please use 
> SYMLINK+= or change the kernel to provide the proper name
> syslog:Jul 22 10:58:05 xenturio1 udevd[8664]: kernel-provided name 
> 'blktap3' and NAME= 'xen/blktap-2/blktap3' disagree, please use 
> SYMLINK+= or change the kernel to provide the proper name

This is because udev and forward/backward compatibility are strangers
passing in the night. I presume if you make the recommended change to
SYMLINK+= instead of NAME= in your udev script this goes away?

> Then i shutdown the guest:
> root@xenturio1:/var/log# xl shutdown x1test
> 
> And i am left with remaining tapdisk2 and udev processes, one for each 
> block device that was assigned to the guest:
> root      8975  0.1  0.0  21664  3256 ?        SLs  11:00   0:00 tapdisk2
> root      8981  0.0  0.0  21664  3256 ?        SLs  11:00   0:00 tapdisk2
> root      8983  0.0  0.0  21008   796 ?        S    11:00   0:00 udevd 
> --daemon
> root      9002  0.0  0.0  21008   800 ?        S    11:00   0:00 udevd 
> --daemon

I posted a patch to fix this "libxl: attempt to cleanup tapdisk
processes on disk backend destroy" a couple of times, most recently at 
http://marc.info/?l=xen-devel&m=131066210526755 but it hasn't been
applied yet. Can you try it?

> I am using Xen 4.1.1 with the 2.6.32.43-pvops kernel from jeremy.
> My distro is debian 6.0.2. that uses udev 164-3.
> I did update it on a different machine to 171-3, but that did not help.
> 
> 
> My xen-backend.rules contains the default:
> SUBSYSTEM=="xen", KERNEL=="blktap[0-9]*", NAME="xen/blktap-2/%k", 
> MODE="0600"
> SUBSYSTEM=="blktap2", KERNEL=="blktap[0-9]*", NAME="xen/blktap-2/%k", 
> MODE="0600
> 
> 
> My questions are:
> - Are the two issues related?
> - How can i fix them?
> 
> 
> I think that eventually this will cause the host to run out of either 
> free process IDs and/or RAM.
> 
>