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SubjectRe: [PATCHSET x86/core/percpu] implement dynamic percpu allocator
Tejun Heo wrote:
> Rusty Russell wrote:
>>>>> Rusty, if the fixes are fine with you i can put those two
>>>>> commits into tip/core/urgent straight away, the full string of
>>>>> 10 commits into tip/core/percpu and thus we'd avoid duplicate
>>>>> (or even conflicting) commits.
>>>> No, the second one is not .29 material; it's a nice, but
>>>> theoretical, fix.
>>> Can it never trigger?
>> Actually, checked again. It's not even necessary AFAICT (tho a comment
>> would be nice):
>>
>> for (i = 0; i < pcpu_num_used; ptr += block_size(pcpu_size[i]), i++) {
>> /* Extra for alignment requirement. */
>> extra = ALIGN((unsigned long)ptr, align) - (unsigned long)ptr;
>> BUG_ON(i == 0 && extra != 0);
>>
>> if (pcpu_size[i] < 0 || pcpu_size[i] < extra + size)
>> continue;
>>
>> /* Transfer extra to previous block. */
>> if (pcpu_size[i-1] < 0)
>> pcpu_size[i-1] -= extra;
>> else
>> pcpu_size[i-1] += extra;
>>
>> pcpu_size[0] is *always* negative: it's marked allocated at initialization
>> (it's the static per-cpu allocations).
>>
>> Sorry I didn't examine more closely,
>
> Ah... okay. Right. I took the code and used it in the chunk area
> allocator where 0 isn't guaranteed to be occupied and saw the problem
> triggering and then assumed the modalloc allocator shared the same
> problem. So, unnecessary fix but I think it really needs some
> explanation.
>
> What to do about #tj-percpu? Ingo, do you want me to rebase tree sans
> the second one?

Ingo, as you haven't pulled already. I'm incorporating changes from
the comments posted till now and rebasing the tree. Please stand by a
bit.

Thanks.

--
tejun


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