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

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Message-ID: <ycbcan5wcxtz2mbywz6zdoyfus26vrhus6enipe543x2ejyt77@m3l4ksir7k2k>
Date:   Thu, 14 Sep 2023 08:01:50 +0200
From:   Maciej Wieczór-Retman 
        <maciej.wieczor-retman@...el.com>
To:     Reinette Chatre <reinette.chatre@...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,

On 2023-09-13 at 11:49:19 -0700, Reinette Chatre wrote:
>Hi Maciej,
>
>On 9/12/2023 10:59 PM, Maciej Wieczór-Retman wrote:
>> On 2023-09-12 at 09:00:28 -0700, Reinette Chatre wrote:
>>> Hi Maciej,
>>>
>>> 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)?

-- 
Kind regards
Maciej Wieczór-Retman