Re: [RFC 0/5] percpu: Optimize percpu accesses

[Mike Travis <travis@sgi.com>]

Ingo Molnar wrote:
> * Ingo Molnar <mingo@elte.hu> wrote:
> 
>>> This patchset provides the following:
>>>
>>>   * Cleanup: Fix early references to cpumask_of_cpu(0)
>>>   * Generic: Percpu infrastructure to rebase the per cpu area to zero
>>>   * x86_64: Fold pda into per cpu area
>>>   * x86_64: Rebase per cpu variables to zero
>> thanks Mike - i've started testing it in -tip. One small merge fallout 
>> fix is below. (it's for the new generic-ipi topic that was not in 
>> tip/master yet when you merged percpu-zerobased to it)
> 
> ok, -tip testing found an early boot crash caused by your patchset, on 
> 64-bit x86:
> 
> [    0.396000] calling  net_ns_init+0x0/0x143
> [    0.400000] net_namespace: 944 bytes
> [    0.403578] BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
> [    0.404000] IP: [<ffffffff80e05b0e>] net_ns_init+0x9f/0x143
> [    0.404000] PGD 0
> [    0.404000] Oops: 0000 [1] SMP
> [    0.404000] CPU 0
> [...]
> 
> full bootlog and config can be found at:
> 
>   http://redhat.com/~mingo/misc/crashlog-Tue_Jul__1_16_48_45_CEST_2008.bad
>   http://redhat.com/~mingo/misc/config-Tue_Jul__1_16_48_45_CEST_2008.bad
> 
> (another 64-bit testbox crashed as well, so this should be readily 
> reproducible.)
> 
> i've pushed this tree out to tip/tmp.core/percpu-zerobased.Jul__1_16_48 
> topic branch, that is the 2.6.26-rc8-tip-00250-g90874b0 kernel you can 
> see in the crashlog.
> 
> 	Ingo

Wow, that was quick!

At least this one gets to someplace debuggable.  Some others that don't
even get to the first "kernel alive" messages are really annoying.  ;-)

Thanks,
Mike