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Date: Fri, 24 Mar 2017 21:14:39 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Andy Lutomirski <luto@kernel.org>
Cc: Dmitry Vyukov <dvyukov@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
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        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@kernel.org>,
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Subject: Re: locking/atomic: Introduce atomic_try_cmpxchg()
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On Fri, Mar 24, 2017 at 12:16:11PM -0700, Andy Lutomirski wrote:
> On Fri, Mar 24, 2017 at 11:13 AM, Peter Zijlstra <peterz@infradead.org> wrote:

> > Not to mention we cannot use the C11 atomics in kernel because we want
> > to be able to runtime patch LOCK prefixes when only 1 CPU is available.
> 
> Is this really a show-stopper?  I bet that objtool could be persuaded
> to emit a list of the locations of all those LOCK prefixes.

Ah, but its not _all_ LOCK prefixes. Some are needed even on UP, because
against hardware instead of other CPUs. Or again hypervisor instead of
other vCPU.