[stgt] Crash tgtd and tgtadm with more than 112 volumes.

FUJITA Tomonori fujita.tomonori at lab.ntt.co.jp
Wed Mar 11 00:55:49 CET 2009

On Tue, 10 Mar 2009 16:48:09 -0700
Ben Greear <greearb at candelatech.com> wrote:

> FUJITA Tomonori wrote:
> > On Tue, 10 Mar 2009 15:34:08 -0700
> > Ben Greear <greearb at candelatech.com> wrote:
> > 
> >> I wrote a script to create lots of iscsi volumes on loop devices.
> >>
> >> Seems to run fine up to 111, and then tgtd crashes and tgtadm
> >> gets a buffer overflow.
> >>
> >> The script I used to create the problem and a capture of the
> >> crash is attached.
> >>
> >> I'm using standard RPMs on Fedora 10, kernel
> >> Linux iSCSi-test #1 SMP Wed Feb 11 23:14:31 EST 2009 x86_64 x86_64 x86_64 GNU/Linux
> >>
> >> Let me know if I can provide any additional info.
> > 
> > Your subject gave me an impression that you are creating lots of
> > logical units with one target but looks like you are trying to create
> > lots of targets with a single logical unit, right?
> I'm new to iscsi, so not so sure of my terminology, but I think
> you have it correct.  I'm working on a test tool that uses open-iscsi
> to mount lots of volumes on a single machine, to be used to load-test
> iscsi target systems.  I was using tgtd as the iscsi target for
> testing my initiator setup.
> > We use pthread and glibc has the limit of the number of
> > pthreads. Looks like you hit it. I guess that tgt also has a bug (tgt
> > should handle pthread creation failure or something properly) though.
> Looks like you can have many more, if this is accurate, and that's
> from 2004:
> http://forum.soft32.com/linux2/Thread-count-limit-ftopict14647.html

I think that 2.4.X kernel's way to handle pthread is different from
2.6.X. So I'm not sure this can be applied to the current situation.

FYI, we consume 2 process + 8 pthread per one target with a single
logica unit.
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