linux-kernel - Re: [PATCH 00/13] atomics: API cleanups

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Message-ID: <20180523171817.GV12198@hirez.programming.kicks-ass.net>
Date:   Wed, 23 May 2018 19:18:17 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Mark Rutland <mark.rutland@....com>
Cc:     linux-kernel@...r.kernel.org, Boqun Feng <boqun.feng@...il.com>,
        Will Deacon <will.deacon@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Richard Henderson <rth@...ddle.net>,
        Ivan Kokshaysky <ink@...assic.park.msu.ru>,
        Matt Turner <mattst88@...il.com>,
        Vineet Gupta <vgupta@...opsys.com>,
        Russell King <linux@...linux.org.uk>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Palmer Dabbelt <palmer@...ive.com>,
        Albert Ou <albert@...ive.com>
Subject: Re: [PATCH 00/13] atomics: API cleanups

On Wed, May 23, 2018 at 02:35:20PM +0100, Mark Rutland wrote:
> This series contains a few cleanups of the atomic API, fixing an
> inconsistency between atomic_* and atomic64_*, and minimizing repetition
> in arch code. This is nicer for arch code, and the improved regularity
> will help when generating the atomic headers in future.
> 
> The bulk of the patches reorganise things so architectures consistently
> provide <atomic>_fetch_add_unless(), with atomic_fetch_add_unless()
> provided as a wrapper by core code. A generic fallback is provided for
> <atomic>_fetch_add_unless(), based on <atomic>_read() and
> <atomic>_try_cmpxchg().
> 
> Other patches in the series add common fallbacks for:
> 
> * atomic64_inc_not_zero() 
> * <atomic>_inc_and_test()
> * <atomic>_dec_and_test()
> * <atomic>_sub_and_test()
> * <atomic>add_negative()
> 
> ... as almost all architectures provide identical implementation of
> these today.
> 
> The end result is a strongly negative diffstat, though <linux/atomic.h>
> grows by a reasonable amount. When we generate the headers, we can halve
> this by templating the various fallbacks for atomic{,64}_t.
> 

Thanks for this Mark,

Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>

Ingo, can you magic this into tip somewhere?