Re: linux-next: Tree for Mar 14 (mips qemu failure bisected)

[Qais Yousef]

This is a multi-part message in MIME format.
On 16/03/2016 20:27, Qais Yousef wrote:
> On 16/03/2016 13:22, Guenter Roeck wrote:
> > On Tue, Mar 15, 2016 at 05:17:13PM -0700, Guenter Roeck wrote:
> > > On Tue, Mar 15, 2016 at 09:55:06PM +0000, Qais Yousef wrote:
> > > > Hi Guenter,
> > [ ... ]
> > > > > > Qemu test results:
> > > > > >     total: 96 pass: 69 fail: 27
> > > > > > Failed tests:
> > > > > [ ... ]
> > > > > >     mips:mips_malta_smp_defconfig
> > > > > I bisected this failure to commit bb11cff327e54 ("MIPS: Make smp 
> > > > > CMP, CPS and MT
> > > > > use the new generic IPI functions". Bisect log is attached.
> > > > Thanks for bisecting this. I tested this on a real Malta system but 
> > > > not
> > > > qemu. I'll try to reproduce.
> > > I run the tests with only a single CPU core enabled. Maybe that causes
> > > problems with your code ?
> > I ran another qemu test (this time on mainline) with "-smp 2", but 
> > the only
> > difference is that the image now gets stuck even earlier.
> >
> > Also, I ran another set of bisects, this time with both mips and mips64
> > on mainline (after your patch landed), with the same results.
> >
> > Guenter
>
> OK thanks for the info. The offending commit just enables using quite 
> a few of the newly added code before that. So the problem could be in 
> any of the newly added code.
>
> Unfortunately I can only look at this during my limited time in the 
> evening and I have to setup my system to compile and run this, so I 
> won't be able to get to the bottom of this as fast as I'd like to.
>
> Qais

OK I was up and running faster than I thought I would be. Can you 
confirm that you're hitting a BUG_ON() in mips_smp_ipi_init()?

What I see is that BUG_ON() is hit because we couldn't find an ipidomain 
to allocate the ipis from. The reason of whih is that the qemu malta 
machine doesn't have a GIC though the config is compiled with GIC on. 
Also if I remember correctly qemu malta doesn't really support SMP. I 
think that was the reason I never ran this on qemu.

I'm not sure what's the best way forward here. I can add a check to 
verify gic_present inside this function and return early. Patch attached.

Ralf, thoughts?

Thanks,
Qais