linux-kernel - Re: [PATCH v2 1/2] nfit: Fix the abuse of COMPLETION_INITIALIZER

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Message-ID: <CAPcyv4gHgdpyqbv8gs5MiEtEHSdC-JLhutdfn81fhQ1woQSh_Q@mail.gmail.com>
Date:   Thu, 24 Aug 2017 17:36:22 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     Boqun Feng <boqun.feng@...il.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Linux MM <linux-mm@...ck.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Michel Lespinasse <walken@...gle.com>,
        Byungchul Park <byungchul.park@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Wilcox <willy@...radead.org>,
        Nicholas Piggin <npiggin@...il.com>, kernel-team@....com,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
        Linux ACPI <linux-acpi@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] nfit: Fix the abuse of COMPLETION_INITIALIZER_ONSTACK()

On Thu, Aug 24, 2017 at 7:22 AM, Boqun Feng <boqun.feng@...il.com> wrote:
> COMPLETION_INITIALIZER_ONSTACK() is supposed to used as an initializer,
> in other words, it should only be used in assignment expressions or
> compound literals. So the usage in drivers/acpi/nfit/core.c:
>
>         COMPLETION_INITIALIZER_ONSTACK(flush.cmp);
>
> , is inappropriate.
>
> Besides, this usage could also break compilations for another fix to
> reduce stack sizes caused by COMPLETION_INITIALIZER_ONSTACK(), because
> that fix changes COMPLETION_INITIALIZER_ONSTACK() from rvalue to lvalue,
> and usage as above will report error:
>
>         drivers/acpi/nfit/core.c: In function 'acpi_nfit_flush_probe':
>         include/linux/completion.h:77:3: error: value computed is not used [-Werror=unused-value]
>           (*({ init_completion(&work); &work; }))
>
> This patch fixes this by replacing COMPLETION_INITIALIZER_ONSTACK() with
> init_completion() in acpi_nfit_flush_probe(), which does the same
> initialization without any other problem.
>
> Signed-off-by: Boqun Feng <boqun.feng@...il.com>

Acked-by: Dan Williams <dan.j.williams@...el.com>