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

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Date:   Wed, 13 Sep 2023 11:49:19 -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 9/12/2023 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.

Reinette