linux-kernel - Re: [PATCH] clocksource/drivers/timer-of: mark timer_of_exit as _

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Date:   Sun, 12 Nov 2017 23:24:56 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        Benjamin Gaignard <benjamin.gaignard@...aro.org>,
        Sudeep Holla <sudeep.holla@....com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] clocksource/drivers/timer-of: mark timer_of_exit as __init

On Sun, Nov 12, 2017 at 10:16 PM, Thomas Gleixner <tglx@...utronix.de> wrote:
> On Mon, 6 Nov 2017, Arnd Bergmann wrote:
>> The newly added function triggers a harmless Kbuild warning because
>> of a missing annotation:
>>
>> WARNING: vmlinux.o(.text+0x448098): Section mismatch in reference from the function timer_of_exit() to the function .init.text:timer_clk_exit()
>> The function timer_of_exit() references
>> the function __init timer_clk_exit().
>> This is often because timer_of_exit lacks a __init
>> annotation or the annotation of timer_clk_exit is wrong.
>>
>> The function is only called from other __init functions, so it
>> can safely be marked as __init as well.
>
> Hmm. I don't see any caller at all. From the intention of the patch I
> assume this isn't designed for using from init functions, so we rather have
> to remove the __init annotations from the called functions.
>
> Sudeep posted a patch which does that:
>
>  https://lkml.kernel.org/r/1509979716-10646-1-git-send-email-sudeep.holla@arm.com
>
> Though I rather would know whether this function is going to be used at
> all and what the intention of this patch was.
>
> Benjamin????

My interpretation was that timer drivers are still supposed to be unregistered
at module unload time, but that you might use the new timer_of_exit()
in the failure path of whatever function calls timer_of_init() successfully
when something fails in the next step.

Sudeep's interpretation also makes sense, I had not thought of that, but
I now found the patch that adds a user in an init function:
https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1519644.html

It seems I guessed right and Sudeep guessed wrong (both by pure chance
I admit). Both patches solve the problem, Sudeep's version is a little
more robust in case we ever add a caller in an __exit function (which I
think is currently not allowed), while mine saves a little bit of memory
and matches the current usage better.

       Arnd