Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1751438AbdHSNeD (ORCPT <rfc822;w@1wt.eu>);
        Sat, 19 Aug 2017 09:34:03 -0400
Received: from mail-oi0-f66.google.com ([209.85.218.66]:38422 "EHLO
        mail-oi0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1751012AbdHSNeC (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Sat, 19 Aug 2017 09:34:02 -0400
MIME-Version: 1.0
In-Reply-To: <CAK8P3a2+OdPX-uvRjhycX1NYNC_cBPv_bxJHcoh1ue2y7UX+Tg@mail.gmail.com>
References: <1502089981-21272-1-git-send-email-byungchul.park@lge.com>
 <1502089981-21272-10-git-send-email-byungchul.park@lge.com>
 <CAK8P3a3ABsxTaS7ZdcWNbTx7j5wFRc0h=ZVWAC_h-E+XbFv+8Q@mail.gmail.com>
 <20170818234348.GE11771@tardis> <CAK8P3a2+OdPX-uvRjhycX1NYNC_cBPv_bxJHcoh1ue2y7UX+Tg@mail.gmail.com>
From: Arnd Bergmann <arnd@arndb.de>
Date: Sat, 19 Aug 2017 15:34:01 +0200
X-Google-Sender-Auth: QwpRXUEE5uBmXHhxTbYWasK2-os
Message-ID: <CAK8P3a3TfZ=_tm0CUC5aKtf5PDwscLYsAN9Tbs2v0iJN5Jz-Rw@mail.gmail.com>
Subject: Re: [PATCH v8 09/14] lockdep: Apply crossrelease to completions
To: Boqun Feng <boqun.feng@gmail.com>
Cc: Byungchul Park <byungchul.park@lge.com>,
        Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Michel Lespinasse <walken@google.com>, kirill@shutemov.name,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux-MM <linux-mm@kvack.org>,
        Andrew Morton <akpm@linux-foundation.org>, willy@infradead.org,
        Nicholas Piggin <npiggin@gmail.com>, kernel-team@lge.com
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 1143
Lines: 32

On Sat, Aug 19, 2017 at 2:51 PM, Arnd Bergmann <arnd@arndb.de> wrote:

>> --- a/include/linux/completion.h
>> +++ b/include/linux/completion.h
>> @@ -74,7 +74,7 @@ static inline void complete_release_commit(struct completion *x) {}
>>  #endif
>>
>>  #define COMPLETION_INITIALIZER_ONSTACK(work) \
>> -       ({ init_completion(&work); work; })
>> +       (*({ init_completion(&work); &work; }))
>>
>>  /**
>>   * DECLARE_COMPLETION - declare and initialize a completion structure
>
> Nice hack. Any idea why that's different to the compiler?
>
> I've applied that one to my test tree now, and reverted my own patch,
> will let you know if anything else shows up. I think we probably want
> to merge both patches to mainline.

There is apparently one user of COMPLETION_INITIALIZER_ONSTACK
that causes a regression with the patch above:

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; }))

It would be trivial to convert to init_completion(), which seems to be
what was intended there.

        Arnd