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

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Message-ID: <20160425082639.GC3430@twins.programming.kicks-ass.net>
Date:	Mon, 25 Apr 2016 10:26:39 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Martin Schwidefsky <schwidefsky@...ibm.com>
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Subject: Re: [RFC][PATCH 19/31] locking,s390: Implement
 atomic{,64}_fetch_{add,sub,and,or,xor}()

On Mon, Apr 25, 2016 at 10:06:25AM +0200, Martin Schwidefsky wrote:
> 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.

So we already have an atomic_fetch_or() user in the kernel, and this
series adds an atomic_fetch_add_acquire() user.

But yes, we'll undoubtedly grow more over time :-)

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

Thanks!