Re: [RFC][PATCH 5/5] arch: Sanitize atomic_t bitwise ops

[Linus Torvalds]

On Thu, Feb 6, 2014 at 9:52 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
>
> s390 is stuffed with atomic_{set,clear}_mask usage, no clue whatfor.

It's not the set/clear_mask ones I would worry about.

It's the "_return" variants. As far as I can tell, there are exactly
ZERO users of that stuff, and they are BAD BAD BAD.

On x86, those things would cause a cmpxchg loop, and the bad
read-for-shared-before-acquire cacheline pattern.

So why indirectly encourage people to add users for a bad operation?

                        Linus
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