[uml-devel] UML Hang / strace fix

["robl" <spam@robl.org.uk>]

Hi,

I posted this on #UML and was asked to repeat it here ...

I've recently installed UML on a Compaq DL360 G1 Dual P3 1Ghz / Debian Sarge

I see intermittent hangs with the UML kernel at :

Initialized stdio console driver
Console initialized on /dev/tty0
Initializing software serial port version 1
 ubda: unknown partition table
kjournald starting.  Commit interval 5 seconds
EXT3-fs: mounted filesystem with ordered data mode.
VFS: Mounted root (ext3 filesystem) readonly.  <----- Hangs here

The processlist at this point is :

root     14553  1.1  1.9 206200 10056 pts/0  S+   00:33   0:00          
linux mem=200M eth0=tuntap,tap1
root     14558  0.0  1.9 206200 10056 pts/0  S+   00:33   0:00             
linux mem=200M eth0=tuntap,tap1
root     14559  0.0  1.9 206200 10056 pts/0  S+   00:33   0:00             
linux mem=200M eth0=tuntap,tap1
root     14560  0.0  1.9 206200 10056 pts/0  S+   00:33   0:00             
linux mem=200M eth0=tuntap,tap1

If I strace -p 14560 then I see :

debian:~# strace -p 14560
Process 14560 attached - interrupt to quit
poll([{fd=15, events=POLLIN, revents=POLLIN}], 1, -1) = 1
read(15, "\0", 1)                       = 1
write(15, "\0", 1)                      = 1
poll(

This then causes the UML kernel to continue booting normally.

It seems a 50/50 success/hang rate.

The UML kernel is Linux (none) 2.6.16 #2 Sat Apr 29 23:36:42 CEST 2006 i686
GNU/Linux

I've tried this with a stock Debian sarge 2.4 and a patched 2.6 skas as the
host kernels both with the same results.

Anybody have any ideas why this hangs and why strace kicks it back into action ?

Thanks,

Rob



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