On Wed, Jan 10, 2018 at 4:54 PM, Christian König
<christian.koenig@xxxxxxx> 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@xxxxxxxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Arnd
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