linux-kernel - Re: [RFC][PATCH 19/31] locking,s390: Implement atomic{,64}_fetch

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Date:	Mon, 25 Apr 2016 10:06:25 +0200
From:	Martin Schwidefsky <schwidefsky@...ibm.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	torvalds@...ux-foundation.org, mingo@...nel.org,
	tglx@...utronix.de, will.deacon@....com,
	paulmck@...ux.vnet.ibm.com, boqun.feng@...il.com,
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	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
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	cmetcalf@...lanox.com, jcmvbkbc@...il.com, arnd@...db.de,
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Subject: Re: [RFC][PATCH 19/31] locking,s390: Implement
 atomic{,64}_fetch_{add,sub,and,or,xor}()

On Fri, 22 Apr 2016 11:04:32 +0200
Peter Zijlstra <peterz@...radead.org> 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).
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> ---
>  arch/s390/include/asm/atomic.h |   42 +++++++++++++++++++++++++++++++----------
>  1 file changed, 32 insertions(+), 10 deletions(-)

That looks good, the code compiles and the functions are generated correctly.
We will know for sure if it works after the first user of these new functions
hit the kernel.

Acked-by: Martin Schwidefsky <schwidefsky@...ibm.com>

-- 
blue skies,
   Martin.

"Reality continues to ruin my life." - Calvin.