On Fri, 14 Nov 2014, Dave Jones wrote:
> On Sat, Nov 15, 2014 at 01:36:41AM +0100, Thomas Gleixner wrote:
> > On Fri, 14 Nov 2014, Dave Jones wrote:
> >
> > > On Fri, Nov 14, 2014 at 11:55:30PM +0100, Thomas Gleixner wrote:
> > >
> > > > So this looks more like a smp function call fuckup.
> > > >
> > > > I assume Dave is running that stuff on KVM. So it might be worth while
> > > > to look at the IPI magic there.
> > >
> > > no, bare metal.
> >
> > Ok, but that does not change the fact that we are stuck in
> > smp_function_call land.
> >
> > Enabling softlockup_all_cpu_backtrace will probably not help much as
> > we will end up waiting for csd_lock again :(
> >
> > Is the machine still accesible when this happens? If yes, we might
> > enable a few trace points and functions and read out the trace
> > buffer. If not, we could just panic the machine and dump the trace
> > buffer over serial.
>
> No, it wedges solid. Even though it says something like "CPU3 locked up",
> aparently all cores also get stuck.
Does not surprise me. Once the smp function call machinery is wedged...
> 9 times out of 10 it doesn't stay alive long enough to even get the full
> trace out over usb-serial.
usb-serial is definitely not the best tool for stuff like this. I
wonder whether netconsole might give us some more info.
Last time I looked into something like that on my laptop I had to
resort to a crash kernel to get anything useful out of the box.
Thanks,
tglx
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