linux-kernel - Re: [PATCH RESEND v3 1/2] selftests/resctrl: Fix schemata write error check

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Message-ID: <6fbc0b65-0f02-3c7f-bd7a-5183d24a1fe5@intel.com>
Date:   Thu, 14 Sep 2023 08:14:25 -0700
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     Maciej Wieczór-Retman 
        <maciej.wieczor-retman@...el.com>
CC:     Fenghua Yu <fenghua.yu@...el.com>, Shuah Khan <shuah@...nel.org>,
        <ilpo.jarvinen@...ux.intel.com>, <linux-kernel@...r.kernel.org>,
        <linux-kselftest@...r.kernel.org>
Subject: Re: [PATCH RESEND v3 1/2] selftests/resctrl: Fix schemata write error
 check

Hi Maciej,

On 9/13/2023 11:01 PM, Maciej Wieczór-Retman wrote:
> On 2023-09-13 at 11:49:19 -0700, Reinette Chatre wrote:
>> On 9/12/2023 10:59 PM, Maciej Wieczór-Retman wrote:
>>> On 2023-09-12 at 09:00:28 -0700, Reinette Chatre wrote:
>>>> On 9/11/2023 11:32 PM, Maciej Wieczór-Retman wrote:
>>>>> On 2023-09-11 at 09:59:06 -0700, Reinette Chatre wrote:
>>>>>> Hi Maciej,
>>>>>> When I build the tests with this applied I encounter the following:
>>>>>>
>>>>>> resctrlfs.c: In function ‘write_schemata’:
>>>>>> resctrlfs.c:475:14: warning: implicit declaration of function ‘open’; did you mean ‘popen’? [-Wimplicit-function-declaration]
>>>>>>  475 |         fd = open(controlgroup, O_WRONLY);
>>>>>>      |              ^~~~
>>>>>>      |              popen
>>>>>> resctrlfs.c:475:33: error: ‘O_WRONLY’ undeclared (first use in this function)
>>>>>>  475 |         fd = open(controlgroup, O_WRONLY);
>>>>>>      |                                 ^~~~~~~~
>>>>>> resctrlfs.c:475:33: note: each undeclared identifier is reported only once for each function it appears in
>>>>>
>>>>> Hmm, that's odd. How do you build the tests?
>>>>
>>>> I applied this series on top of kselftest repo's "next" branch.
>>>>
>>>> I use a separate build directory and first ran "make headers". After that,
>>>> $ make O=<build dir> -C tools/testing/selftests/resctrl
>>>
>>> I do the same, just without the build directory, but that shouldn't
>>> matter here I guess.
>>>
>>>>> I use "make -C tools/testing/selftests/resctrl" while in the root kernel
>>>>> source directory. I tried to get the same error you experienced by
>>>>> compiling some dummy test program with "open" and "O_WRONLY". From the
>>>>> experiment I found that the "resctrl.h" header provides the declarations
>>>>> that are causing your errors.
>>>>
>>> >From what I can tell resctrl.h does not include fcntl.h that provides
>>>> what is needed.
>>>
>>> I found out you can run "gcc -M <file>" and it will recursively tell you
>>> what headers are including other headers.
>>>
>>> Using this I found that "resctrl.h" includes <sys/mount.h> which in turn
>>> includes <fcntl.h> out of /usr/include/sys directory. Is that also the
>>> case on your system?
>>>
>>
>> No. The test system I used is running glibc 2.35 and it seems that including
>> fcntl.h was added to sys/mount.h in 2.36. See glibc commit
>> 78a408ee7ba0 ("linux: Add open_tree")
>>
>> Generally we should avoid indirect inclusions and here I think certainly so
>> since it cannot be guaranteed that fcntl.h would be available via 
>> sys/mount.h.
> 
> Okay, would including the fcntl.h header to resctrl.h be okay in this
> case? Or is there some other more sophisticated way of doing that (some
> include guard or checking glibc version for example)?

Ideally fcntl.h would be included in the file it is used. Doing so you may
encounter the same problems as Ilpo in [1]. If that is the case and that fix works
for you then you may want to have this series depend on Ilpo's work.

Reinette

[1] https://lore.kernel.org/lkml/dfc53e-3f92-82e4-6af-d1a28e8c199a@linux.intel.com/