linux-kernel - Re: [RFC][PATCH 05/31] locking,arm64: Implement atomic{,64}_fetch_{add,sub,and,andnot,or,xor}{,_relaxed,_acquire,

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Message-ID: <20160422110832.GB10289@arm.com>
Date:	Fri, 22 Apr 2016 12:08:33 +0100
From:	Will Deacon <will.deacon@....com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	torvalds@...ux-foundation.org, mingo@...nel.org,
	tglx@...utronix.de, paulmck@...ux.vnet.ibm.com,
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Subject: Re: [RFC][PATCH 05/31] locking,arm64: Implement
 atomic{,64}_fetch_{add,sub,and,andnot,or,xor}{,_relaxed,_acquire,_release}()

On Fri, Apr 22, 2016 at 11:04:18AM +0200, Peter Zijlstra wrote:
> Implement FETCH-OP atomic primitives, these are very similar to the
> existing OP-RETURN primitives we already have, except they return the
> value of the atomic variable _before_ modification.
> 
> This is especially useful for irreversible operations -- such as
> bitops (because it becomes impossible to reconstruct the state prior
> to modification).
> 
> XXX lacking LSE bits

I'll cook a patch for this, but thanks for the series.

Will