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Message #169980
[Bug 1556096] Re: [Ubuntu 16.04.1] RELEASE and ACQUIRE atomics on Power
Hi Breno,
Seeing as we are a week before Kernel Freeze for Xenial, I wanted to
check in here and see what the status is for these patches. Have these
officially landed upstream and should we be picking them up for 16.04?
** Changed in: linux (Ubuntu)
Assignee: Canonical Kernel Team (canonical-kernel-team) => Breno Leitão (breno-leitao)
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https://bugs.launchpad.net/bugs/1556096
Title:
[Ubuntu 16.04.1] RELEASE and ACQUIRE atomics on Power
Status in linux package in Ubuntu:
Incomplete
Bug description:
Will Deacon proposed the RELEASE/ACQUIRE/RELAXED semantics for atomic
operations(https://lkml.org/lkml/2015/8/6/498), which has been already
merged in 4.3-rc1. More people tend to use it for better
performance(https://lkml.org/lkml/2015/9/20/47). These semantics are
proposed for better fitting the need of high scalability.
However, the efficient implementation hasn't been merged yet. As we
have a weaker memory order model on POWER, if we didn't implement
these atomics efficently, there would be no benefit we can gain from
these new operations.
A proposal of an efficient implemenation has been sent out to
upstream(https://lkml.org/lkml/2015/9/16/527), hopefully will get
merged. Still there may be more atomics having RELEASE and ACQUIRE
semantics, and there need more effort to implement them correctly.
Also, we need to spread these new atomic variants to LTC kernel team
to understand what they can provide and how to use them.
> Was this feature already accepted upstream?
Not yet, still waiting to get into the maintainer's tree, but there is
no obvious objection to this feature.
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