Re: Seeing "huh, entered softirq 8 ffffffff802682aa preempt_count00000100, exited with 00010100?" in tip.git

[Jeremy Fitzhardinge]

Paul E. McKenney wrote:
> On Thu, Jan 29, 2009 at 02:12:31PM -0800, Jeremy Fitzhardinge wrote:
>   
> > When I boot my x86-64 tip.git kernel under Xen, I'm seeing:
> >
> > pnp: PnP ACPI: disabled
> > NET: Registered protocol family 2
> > huh, entered softirq 8 ffffffff802682aa preempt_count 00000100, exited with 
> > 00010100?
> > IP route cache hash table entries: 512 (order: 0, 4096 bytes)
> > TCP established hash table entries: 1024 (order: 2, 16384 bytes)
> > [...]
> > XENBUS: Device with no driver: device/console/0
> > Freeing unused kernel memory: 372k freed
> > Red Hat nash version 6.0.19 starting
> > Mounting proc filesystem
> > Mounting sysfs filesystem
> > Creating /dev
> > BUG: scheduling while atomic: swapper/0/0x00010000
> > Modules linked in:
> > Pid: 0, comm: swapper Not tainted 2.6.29-rc3-tip #481
> > Call Trace:
> > [<ffffffff80238c1f>] __schedule_bug+0x62/0x66
> > [<ffffffff80211d2d>] ? retint_restore_args+0x5/0x20
> > [<ffffffff80503921>] __schedule+0x95/0x792
> > [<ffffffff802093aa>] ? _stext+0x3aa/0x1000
> > [<ffffffff802093aa>] ? _stext+0x3aa/0x1000
> > [<ffffffff805040c2>] schedule+0xe/0x22
> > [<ffffffff8020ff04>] cpu_idle+0x70/0x72
> > [<ffffffff804fc3a0>] cpu_bringup_and_idle+0x13/0x15
> > Creating initial device nodes
> > Setting up hotplug.
> >
> >
> > From what I can see, softirq 8 is the RCU softirq.  I don't know if the 
> > "scheduling while atomic" is related or not, but its two new schedulerish 
> > symptoms appearing at once, so I think its likely they're related.
> >     
>
> Hmmm...  Mysterious, as you seem to be using classic RCU, which hasn't
> changed in awhile.  Which branch of the tip tree are you using?
>   

tip/master.  It looks like this appeared since -rc1.  Mu current 
suspicion is the percpu changes, since I'm seeing some other strange 
symptoms.

   J
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