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Date: Thu, 6 Feb 2014 19:09:30 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
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Subject: Re: [RFC][PATCH 5/5] arch: Sanitize atomic_t bitwise ops
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On Thu, Feb 06, 2014 at 09:56:54AM -0800, Linus Torvalds wrote:
> On Thu, Feb 6, 2014 at 9:52 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> 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?

OK, I'll not generate the _return() variants.