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

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Date:   Mon, 13 Nov 2017 15:58:32 +0100
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Sudeep Holla <sudeep.holla@....com>, Arnd Bergmann <arnd@...db.de>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Benjamin Gaignard <benjamin.gaignard@...aro.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] clocksource/drivers/timer-of: mark timer_of_exit as
 __init

On 13/11/2017 11:11, Sudeep Holla wrote:
> On Sun, Nov 12, 2017 at 11:24:56PM +0100, Arnd Bergmann wrote:
>> 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).
> 
> Ah OK, I just went by name that it will be called by some exit/remove
> function.
> 
>> 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.
>>
> 
> Agreed, may be if we add users which is called from init functions, the
> warning should disappear. Also as tglx suggested, we could rename if it's
> just used from init function error/exit paths.

The drivers are not compiled as module AFAICT, the function will be
called in the init error path.


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