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

[Igor Mammedov <imammedo@xxxxxxxxxx>]

On 08/24/2011 05:36 PM, Konrad Rzeszutek Wilk wrote:
> 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?
I've applied patches:
sched-separate-the-scheduler-entry-for-preemption.patch
sched-move-blk_schedule_flush_plug-out-of-__schedule.patch
block-shorten-interrupt-disabled-regions.patch

Unfortunately these patches don't help, the problem is still there.

> > --
> > Thanks,
> >   Igor
> >
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--
Thanks,
 Igor

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