Re: 2.6.21-rc5-mm4

[Badari Pulavarty]

On Tue, 2007-04-03 at 15:59 -0700, Christoph Lameter wrote:
> On Tue, 3 Apr 2007, Badari Pulavarty wrote:
> 
> > > > SLUB code hangs my ppc64 machine on boot.
> > > 
> > > Could you enable NMI or something and get me a stackdump? PPC is notorious 
> > > for having strange NUMA issues. Any fallbacks from node 0 on bootstrap? Is 
> > > there memory on node 0?
> > 
> > 
> > Seems to be an issue with calibrate_delay() spinning in a tight
> > loop :(
> > 
> > BTW, machine boots fine with SLAB code - not sure why ?
> 
> SLUB does not guarantee the special casing that SLAB provides for 
> page sized allocations via kmalloc. SLAB aligns page sized allocations on 
> page boundaries and does not allow full debugging of page sized 
> allocations in order to keep these slabs on page sized boundaries.
> 
> I suspect this is related. I could add the same special casing to SLUB. 
> But I really wish we would get rid of special slab behavior depending on 
> the size of the slab. Maybe there is no way around it. Sigh.
> 
> What is the data that calibrate delay is looking at?


Its stuck in following .. 

                while ((loops_per_jiffy <<= 1) != 0) {
                        /* wait for "start of" clock tick */
                        ticks = jiffies;
                        while (ticks == jiffies)
                                /* nothing */;
                        /* Go .. */
                        ticks = jiffies;
                        __delay(loops_per_jiffy);
                        ticks = jiffies - ticks;
                        if (ticks)
                                break;
                }

Its stuck in (tight loop)

	while (ticks == jiffies)
                   /* nothing */;

I have no idea, what this code is supposed to be doing :(
Let me know, what I can do for you.

Thanks,
Badari

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