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Re: [libvirt] Problem in handling fast prints from QEMU to stderr



Hi,

QEMU is spewing this junk because I'm debugging it and added debug
prints to code in its initialization code.

Thanks,
Saul


On Thu, Nov 26, 2009 at 1:51 PM, Daniel P. Berrange <berrange redhat com> wrote:
> On Wed, Nov 25, 2009 at 06:49:24PM +0200, Saul Tamari wrote:
>> Hi,
>>
>> I think I spotted a bug in the way libvirtd handles stderr output from QEMU VMs.
>>
>> When starting a VM and QEMU outputs too much output data to stderr
>> (during a given time period), libvirtd will fail and report the
>> following error to /var/log/messages:
>> libvirtd: 13:44:40.695: error : internal error Out of space while
>> reading console log output
>>
>> I looked at the libvirt code a bit and it seems like the
>> stderr-handling code (I think its in qemudReadLogOutput()) is
>> time-dependent and if a 4K buffer overflows it will stop running this
>> VM.
>> As a workaround I added some usleep(250000) near the fprintf() calls
>> (inside QEMU) and I now manage to get the VM running.
>>
>> Is this the way libvirtd is supposed to behave?
>
> We only look at stdout to find the path for the PTY based char devices.
> This is the first thing QEMU prints out to stderr when operating normally
> and easily fits in 4K.  So the real question is why is your QEMU binary
> spewing so much junk to stdout/stderr before the PTY paths ?  Is there
> anything of interest in /var/log/libvirt/qemu/$GUESTNAME.log
>
> Regards,
> Daniel
> --
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