linux-kernel - Re: next/master build: 198 builds: 1 failed, 197 passed, 1 error, 148 warnings (next-20180110)

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Date:   Wed, 10 Jan 2018 17:18:25 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Christian König <christian.koenig@....com>
Cc:     "kernelci.org bot" <bot@...nelci.org>,
        Kernel Build Reports Mailman List 
        <kernel-build-reports@...ts.linaro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Thomas Hellstrom <thellstrom@...are.com>,
        Dave Airlie <airlied@...hat.com>, Roger He <Hongbo.He@....com>,
        Maarten Lankhorst <maarten.lankhorst@...onical.com>,
        Francisco Jerez <currojerez@...eup.net>,
        Viresh Kumar <vireshk@...nel.org>,
        Shiraz Hashim <shiraz.linux.kernel@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>
Subject: Re: next/master build: 198 builds: 1 failed, 197 passed, 1 error, 148
 warnings (next-20180110)

On Wed, Jan 10, 2018 at 4:54 PM, Christian König
<christian.koenig@....com> wrote:
> Hi Arnd,
>
> Am 10.01.2018 um 16:45 schrieb Arnd Bergmann:
>>>
>>> 14 drivers/gpu/drm/ttm/ttm_page_alloc_dma.c:1186:2: warning: ignoring
>>> return value of 'register_shrinker', declared with attribute
>>> warn_unused_result [-Wunused-result]
>>> 14 drivers/gpu/drm/ttm/ttm_page_alloc.c:485:2: warning: ignoring return
>>> value of 'register_shrinker', declared with attribute warn_unused_result
>>> [-Wunused-result]
>>
>> ttm and kvm are now the last user of register_shrinker that doesn't
>> propagate the return code to its
>> caller, all other callers got fixed in one way or another.
>>
>> I tried to fix this one too, but couldn't come up with a proper way of
>> unwinding both
>> kobject_init_and_add() and ttm_pool_mm_shrink_init():
>>
>>          ret = kobject_init_and_add(&_manager->kobj, &ttm_pool_kobj_type,
>>                                     &glob->kobj, "pool");
>>          if (unlikely(ret != 0)) {
>>                  kobject_put(&_manager->kobj);
>>                  _manager = NULL;
>>                  return ret;
>>          }
>>
>>          ttm_pool_mm_shrink_init(_manager);
>>
>> Calling kobject_put() after a failed kobject_init_and_add() seemed wrong,
>> and it also appears to be missing a kfree(), so I didn't want to mess it
>> up any further. Added a few people to Cc that touched this file most,
>> maybe one of them can have a look, or they already have a patch waiting
>> to get merged.
>
>
> That isn't urgent, isn't it? So I would say I put it on my TODO list and I'm
> going to take care of it no later than 4.17.
>
> Otherwise Roger or me could take a look tomorrow.

My understanding is that the warning will be in 4.16, so the fix should be
as well, if only to get a clean build again. There were around a dozen such
warnings when the warn_unused_result got added, but the others are all
fixed in linux-next.

This is how the flag got added:

commit 64067c5cbfa24a2202b92e8fda7323610cad3043
Author: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Date:   Fri Jan 5 13:25:45 2018 +1100

    mm,vmscan: mark register_shrinker() as __must_check

    There are users not checking for register_shrinker() failure.  Continuing
    with ignoring failure can lead to later oops at unregister_shrinker().

    Link: http://lkml.kernel.org/r/1511265757-15563-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp
    Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>


        Arnd