Messages in this thread | | | Date | Wed, 14 Nov 2018 08:10:52 +0100 | From | Michal Hocko <> | Subject | Re: UBSAN: Undefined behaviour in mm/page_alloc.c |
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On Tue 13-11-18 15:29:41, Andrew Morton wrote: [...] > But do we really need to do this? Are there any other known potential > callsites?
The main point is that the code as it stands is quite fragile, isn't it? Fixing up all the callers is possible but can you actually think of a reason why this would cause any measurable effect in the fast path? The order argument is usually in a register and comparing it to a number with unlikely branch should be hardly something visible.
Besides that we are talking few cycles at best compared to a fragile code that got broken by accident without anybody noticing for quite some time.
I vote for the maintainability over few cycles here. Should anybody find this measurable we can rework the code by other means.
-- Michal Hocko SUSE Labs
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