Jeremy Fitzhardinge
2011-Sep-28 21:40 UTC
[Xen-devel] blkback stuck in infinite loop in xen_blkbk_discard()
I just "xl destroy"d a domain, and now my dom0 kernel is sitting there
infinitely spewing:
vbd vbd-83-51712: 5 reading type
vbd vbd-83-51712: 5 reading type
vbd vbd-83-51712: 5 reading type
vbd vbd-83-51712: 5 reading type
vbd vbd-83-51712: 5 reading type
vbd vbd-83-51712: 5 reading type
vbd vbd-83-51712: 5 reading type
vbd vbd-83-51712: 5 reading type
vbd vbd-83-51712: 5 reading type
vbd vbd-83-51712: 5 reading type
vbd vbd-83-51712: 5 reading type
vbd vbd-83-51712: 5 reading type
vbd vbd-83-51712: 5 reading type
vbd vbd-83-51712: 5 reading type
vbd vbd-83-51712: 5 reading type
vbd vbd-83-51712: 5 reading type
vbd vbd-83-51712: 5 reading type
vbd vbd-83-51712: 5 reading type
vbd vbd-83-51712: 5 reading type
which seems to be coming from the error case in
drivers/block/xen-blkback/xenbus.c:xen_blkbk_discard().
I don''t know what the backtrace is. The system seems overall fine,
despite the console spew, though I have a pile of dying domains sitting
in odd states rather than being cleaned up.
J
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Jan Beulich
2011-Sep-29 09:55 UTC
Re: [Xen-devel] blkback stuck in infinite loop in xen_blkbk_discard()
>>> On 28.09.11 at 23:40, Jeremy Fitzhardinge <jeremy@goop.org> wrote: > I just "xl destroy"d a domain, and now my dom0 kernel is sitting there > infinitely spewing: > > vbd vbd-83-51712: 5 reading type > vbd vbd-83-51712: 5 reading type > vbd vbd-83-51712: 5 reading type > vbd vbd-83-51712: 5 reading type > vbd vbd-83-51712: 5 reading type > vbd vbd-83-51712: 5 reading type > vbd vbd-83-51712: 5 reading type > vbd vbd-83-51712: 5 reading type > vbd vbd-83-51712: 5 reading type > vbd vbd-83-51712: 5 reading type > vbd vbd-83-51712: 5 reading type > vbd vbd-83-51712: 5 reading type > vbd vbd-83-51712: 5 reading type > vbd vbd-83-51712: 5 reading type > vbd vbd-83-51712: 5 reading type > vbd vbd-83-51712: 5 reading type > vbd vbd-83-51712: 5 reading type > vbd vbd-83-51712: 5 reading type > vbd vbd-83-51712: 5 reading type > > which seems to be coming from the error case in > drivers/block/xen-blkback/xenbus.c:xen_blkbk_discard(). > > I don''t know what the backtrace is. The system seems overall fine, > despite the console spew, though I have a pile of dying domains sitting > in odd states rather than being cleaned up.I wonder how the function gets called during destroy in the first place, and how that would prevent destroying a domain (unless there''s a feedback loop due to the use of xenbus_dev_fatal() here, causing some xenstore entry to get written over and over again, triggering the respective watch that blkback has active). But irrespective of this I would think the function should bail without doing anything if blkif->blk_backend_type was already set (or couldn''t get set). But that would then also indicate a more general problem in connect(), as that function shouldn''t do anything either when a domain gets destroyed. Jan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Jeremy Fitzhardinge
2011-Sep-29 16:40 UTC
Re: [Xen-devel] blkback stuck in infinite loop in xen_blkbk_discard()
On 09/29/2011 02:55 AM, Jan Beulich wrote:>>>> On 28.09.11 at 23:40, Jeremy Fitzhardinge <jeremy@goop.org> wrote: >> I just "xl destroy"d a domain, and now my dom0 kernel is sitting there >> infinitely spewing: >> >> vbd vbd-83-51712: 5 reading type >> vbd vbd-83-51712: 5 reading type >> vbd vbd-83-51712: 5 reading type >> vbd vbd-83-51712: 5 reading type >> vbd vbd-83-51712: 5 reading type >> vbd vbd-83-51712: 5 reading type >> vbd vbd-83-51712: 5 reading type >> vbd vbd-83-51712: 5 reading type >> vbd vbd-83-51712: 5 reading type >> vbd vbd-83-51712: 5 reading type >> vbd vbd-83-51712: 5 reading type >> vbd vbd-83-51712: 5 reading type >> vbd vbd-83-51712: 5 reading type >> vbd vbd-83-51712: 5 reading type >> vbd vbd-83-51712: 5 reading type >> vbd vbd-83-51712: 5 reading type >> vbd vbd-83-51712: 5 reading type >> vbd vbd-83-51712: 5 reading type >> vbd vbd-83-51712: 5 reading type >> >> which seems to be coming from the error case in >> drivers/block/xen-blkback/xenbus.c:xen_blkbk_discard(). >> >> I don''t know what the backtrace is. The system seems overall fine, >> despite the console spew, though I have a pile of dying domains sitting >> in odd states rather than being cleaned up. > I wonder how the function gets called during destroy in the first place, > and how that would prevent destroying a domain (unless there''s a > feedback loop due to the use of xenbus_dev_fatal() here, causing > some xenstore entry to get written over and over again, triggering > the respective watch that blkback has active). > > But irrespective of this I would think the function should bail without > doing anything if blkif->blk_backend_type was already set (or > couldn''t get set). But that would then also indicate a more general > problem in connect(), as that function shouldn''t do anything either > when a domain gets destroyed.Well, it could have got into that state before I destroyed the domain - it was a test kernel that crashed very early (before setting up its own frontend) after booting from pvgrub, so perhaps there was some race in that handoff. J _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel