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SubjectRe: [PATCH] locking/qspinlock: Use atomic_sub_return_release in queued_spin_unlock
On Fri, 03 Jun 2016, Pan Xinhui wrote:

>The existing version uses a heavy barrier while only release semantics
>is required. So use atomic_sub_return_release instead.
>
>Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
>Signed-off-by: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>

I just noticed this change in -tip and, while I know that saving a barrier
in core spinlock paths is perhaps a worthy exception, I cannot help but
wonder if this is the begging of the end for smp__{before,after}_atomic().

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