Messages in this thread | | | Date | Tue, 01 Dec 2009 13:40:05 +0800 | From | Cong Wang <> | Subject | Re: [PATCH] percpu: explain quick paths in pcpu_[de]populate_chunk() |
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Tejun Heo wrote: > On 12/01/2009 02:00 PM, Tejun Heo wrote: >> I thought about that but didn't want to open code the special and >> fairly complex loop construct used there. To me, it seemed using the >> same loop construct would be much less error-prone than open coding >> the loop mostly because those two special cases are the only place >> where that is necessary. Maybe we can add pcpu_first_[un]pop_region() >> macros and use them there but is the first iteration check that bad >> even with sufficient explanations? > > So, something like the following.
Thanks for working on this.
> > #define pcpu_first_unpop_region(chunk, rs, re, start, end) do { \ > (rs) = (start); \ > pcpu_next_unpop((chunk), &(rs), &(re), (end)); \ > } while (0) > > #define pcpu_for_each_unpop_region(chunk, rs, re, start, end) \ > for (pcpu_first_unpop_region(chunk, rs, re, start, end); \ > (rs) < (re); \ > (rs) = (re) + 1, pcpu_next_unpop((chunk), &(rs), &(re), (end))) > > #define pcpu_first_pop_region(chunk, rs, re, start, end) do { \ > (rs) = (start); \ > pcpu_next_pop((chunk), &(rs), &(re), (end)); \ > } while (0) > > #define pcpu_for_each_pop_region(chunk, rs, re, start, end) \ > for (pcpu_first_pop_region(chunk, rs, re, start, end); \ > (rs) < (re); \ > (rs) = (re) + 1, pcpu_next_pop((chunk), &(rs), &(re), (end))) > > It might be better to make these proper functions which take pointers > but that makes the only two interfaces for region iterators disagree > about how they take parameters. > > So, I don't know. The first iteration only loop looks a bit unusual > for sure but it isn't something conceptually convoluted.
Now this seems to be better. So with this change, we can do:
pcpu_first_pop_region(chunk, rs, re, start, end); if (rs < re && ...) return;
Right?
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