Re: [Xen-devel] Re: [PATCH] blkfront: Move blkif_interrupt into a tasklet.

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Wed, Aug 17, 2011 at 11:07:19AM +0200, Igor Mammedov wrote:
> On 08/17/2011 04:38 AM, Konrad Rzeszutek Wilk wrote:
> >On Tue, Aug 16, 2011 at 04:26:55AM -0700, imammedo wrote:
> >>
> >>Jeremy Fitzhardinge wrote:
> >>>
> >>>Have you tried bisecting to see when this particular problem appeared?
> >>>It looks to me like something is accidentally re-enabling interrupts -
> >>>perhaps a stack overrun is corrupting the "flags" argument between a
> >>>spin_lock_irqsave()/restore pair.
> >>>
> >>>Is it only on 32-bit kernels?
> >>>
> >>  ------------[ cut here ]------------
> >>[604001.659925] WARNING: at block/blk-core.c:239 blk_start_queue+0x70/0x80()
> >>[604001.659964] Modules linked in: nfs lockd fscache auth_rpcgss nfs_acl
> >>sunrpc ip6t_REJECT nf_conntrack_ipv6 nf_conntrack_ipv4 nf_defrag_ipv4
> >>nf_defrag_ipv6 xt_state nf_conntrack ip6table_filter ip6_tables xen_netfront
> >>pcspkr [last unloaded: scsi_wait_scan]
> >>[604001.660147] Pid: 336, comm: udevd Tainted: G        W   3.0.0+ #50
> >>[604001.660181] Call Trace:
> >>[604001.660209]  [<c045c512>] warn_slowpath_common+0x72/0xa0
> >>[604001.660243]  [<c06643a0>] ? blk_start_queue+0x70/0x80
> >>[604001.660275]  [<c06643a0>] ? blk_start_queue+0x70/0x80
> >>[604001.660310]  [<c045c562>] warn_slowpath_null+0x22/0x30
> >>[604001.660343]  [<c06643a0>] blk_start_queue+0x70/0x80
> >>[604001.660379]  [<c075e231>] kick_pending_request_queues+0x21/0x30
> >>[604001.660417]  [<c075e42f>] blkif_interrupt+0x19f/0x2b0
> >>...
> >>  ------------[ cut here ]------------
> >>
> >>I've debugged a bit blk-core warning and can say:
> >>   - Yes, It is 32-bit PAE kernel and happens only with it so far.
> >>   - Affects PV xen guest, bare-metal and kvm configs are not affected.
> >>   - Upstream kernel is affected as well.
> >>   - Reproduces on xen 4.1.1 and 3.1.2 hosts
> >
> >And the dom0 is 2.6.18 right? This problem is not present
> >when you use a 3.0 dom0?
> 
> For xen 4.1.1 testing, I've used as dom0 Jeremy's 2.6.32.43

Jeremy pointed me to this:
https://patchwork.kernel.org/patch/1091772/
(and 
http://groups.google.com/group/linux.kernel/browse_thread/thread/39a397566cafc979)
which looks to have a similar  backtrack.

Perhaps Peter's fix solves the issue?
> 
> -- 
> Thanks,
>  Igor
> 
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