arm SMP fix

[Olivier Houchard]

On Fri, Nov 22, 2013 at 11:21:40AM +0400, Ruslan Bukin wrote:
> On Fri, Nov 22, 2013 at 12:04:57AM +0000, Olivier Houchard wrote:
> > Hi all,                                                                         
> > 
> > Attached is the first draft to a patch that fixes SMP for me, it seems to       
> > work fine on my Pandaboard.                                                     
> > The problem is, as it is currently implemented, curthread is basically          
> > defined as get_pcpu()->pc_curthread. If we get interrupted between the moment   
> > we got the struct pcpu, and the moment we derefence it to get the curthread 
> > pointer, and migrated to another core, we would get the wrong curthread, and    
> > that's not good.                                                                
> > The proposed fix does the following :                                           
> > - use the register we used to use for pcpu for curthread                        
> > - get the pcpu address by reading the cpu id from the CPUID register, and       
> > just use it as an index for the __pcpu array.                                   
> >                                                                                 
> > It breaks the KBI, which is unfortunate, but I think it is no big deal for      
> > arm right now.                                                                  
> >                                                                                 
> > Any review, comment, and testing, even on UP boards, would be very welcome.     
> >                                                                                 
> > Regards,                                                                        
> > 
> > Olivier 
> 
> what type of media for root you used?
> 
> just a quick test on exynos5250
> 
> one time I booted OK with patch and SMP enabled,
> two other attempts got panics
> (probably during usb ethernet load)
> 
> http://pastebin.com/H129SMKX
> http://pastebin.com/szkBjaT5
> 

Hi,

I'm netbooting using the Pandaboard usb ethernet adapter too.
As you're not alone in reporting that my patch doesn't work, I guess I can't
just pretend it's your fault :)
Are you getting the same thing without the patch ?

Regards,

Olivier