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

Mike Travis
2008-07-02T14:04:18Z

Mike Travis wrote:
> 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:

Hi Ingo,

Which gcc version are you using?

Thanks,
Mike

>>
>> [ 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