linux-kernel - Re: [PATCHv4 03/28] posix-clocks: add another call back to return clock time in ktime

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Message-ID: <af700944-694c-822b-4633-7de945f9d228@gmail.com>
Date:   Fri, 14 Jun 2019 15:39:13 +0100
From:   Dmitry Safonov <0x7f454c46@...il.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Dmitry Safonov <dima@...sta.com>
Cc:     linux-kernel@...r.kernel.org, Andrei Vagin <avagin@...il.com>,
        Adrian Reber <adrian@...as.de>,
        Andrei Vagin <avagin@...nvz.org>,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Cyrill Gorcunov <gorcunov@...nvz.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Jann Horn <jannh@...gle.com>, Jeff Dike <jdike@...toit.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Pavel Emelyanov <xemul@...tuozzo.com>,
        Shuah Khan <shuah@...nel.org>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        containers@...ts.linux-foundation.org, criu@...nvz.org,
        linux-api@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCHv4 03/28] posix-clocks: add another call back to return
 clock time in ktime_t

Hi Thomas,

Thanks much for the review,

On 6/14/19 2:32 PM, Thomas Gleixner wrote:
> Dmitry,
> 
> On Wed, 12 Jun 2019, Dmitry Safonov wrote:
> 
>> From: Andrei Vagin <avagin@...il.com>
>>
>> The callsite in common_timer_get() has already a comment:
>>         /*
>>          * The timespec64 based conversion is suboptimal, but it's not
>>          * worth to implement yet another callback.
>>          */
>>         kc->clock_get(timr->it_clock, &ts64);
>>         now = timespec64_to_ktime(ts64);
>>
>> Now we are going to add time namespaces and we need to be able to get:
> 
> Please avoid 'we' and try to describe the changes in a neutral technical
> form, e.g.:
> 
>  The upcoming support for time namespaces requires to have access to:
> 
>> * clock value in a task time namespace to return it from the clock_gettime
>>   syscall.
> 
>   - The time in a tasks time namespace for sys_clock_gettime()
> 
>> * clock valuse in the root time namespace to use it in
>>   common_timer_get().
> 
>   - The time in the root name space for common_timer_get()
> 
>> It looks like another reason why we need a separate callback to return
>> clock value in ktime_t.
> 
>  That adds a valid reason to finally implement a separate callback which
>  returns the time in ktime_t format.
> 
> Hmm?

Agree, the patch has become bigger than wanted and the message could
have been better in technical sense. Will split, add kernel doc and fix
the commit message(s).

[..]
> TBH, this patch is way to big. It changes too many things at once. Can you
> please structure it this way:
> 
>  1) Rename k_clock::clock_get to k_clock::clock_get_timespec and fix up all
>     struct initializers
> 
>  2) Rename the clock_get_timespec functions per instance
> 
>  3) Add the new callback
> 
>  4) Add the new functions per instance and add them to the corresponding
>     struct initializers
> 
>  5) Use the new callback
> 
Thanks,
          Dima