linux-kernel - Re: [PATCHv2 05/16] atomics: prepare for atomic64_fetch_add

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Date:   Tue, 5 Jun 2018 11:26:37 +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: [PATCHv2 05/16] atomics: prepare for atomic64_fetch_add_unless()

On Tue, May 29, 2018 at 04:43:35PM +0100, Mark Rutland wrote:
>  /**
> + * atomic64_add_unless - add unless the number is already a given value
> + * @v: pointer of type atomic_t
> + * @a: the amount to add to v...
> + * @u: ...unless v is equal to u.
> + *
> + * Atomically adds @a to @v, so long as @v was not already @u.
> + * Returns non-zero if @v was not @u, and zero otherwise.

I always get confused by that wording; would something like: "Returns
true if the addition was done" not be more clear?

> + */
> +#ifdef atomic64_fetch_add_unless
> +static inline int atomic64_add_unless(atomic64_t *v, long long a, long long u)

Do we want to make that a "bool' return?

> +{
> +	return atomic64_fetch_add_unless(v, a, u) != u;
> +}
> +#endif