Re: [Xen-devel] Xen blktap driver for Ceph RBD : Anybody wants to test ? :p

[Sylvain Munaut <s.munaut@xxxxxxxxxxxxxxxxxxxx>]

Hi Frederik,

>> A traceback would be great if you can get a core file. And possibly
>> compile tapdisk with debug symbols.
>
> I'm not quite sure what u mean, can u give some more information on how I do
> this? I compiled tapdisk with ./configure CFLAGS=-g, but I'm not sure this
> is what u meant.

Yes, ./configure CFLAGS=-g LDFLAGS=-g  is a good start.

Then when it crashes, if will leave a 'core' time somewhere. (not sure
where, maybe in / or in /tmp)
If it doesn't you may have to enable it. When the process is running,
use this on the tapdisk PID :

http://superuser.com/questions/404239/setting-ulimit-on-a-running-process

Then once you have a core file, you can use gdb along with the tapdisk
executable to generate a meaningful backtrace of where the crash
happenned :

See for ex http://publib.boulder.ibm.com/httpserv/ihsdiag/get_backtrace.html
for how to do it.


> When halting the domU after the errors, I get the following in dom0 syslog:

It's not really unexpected. If tapdisk crashes the IO ring is going to
be left hanging and god knows what weird behaviour will happen ...


Cheers,

    Sylvain

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