linux-kernel - Re: [UML] 3.16 build without optimization fails

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Message-ID: <CAFLxGvyr-ham--zwR32JnXTy+gd9oe6pksSWBpHm-aiS80Tp0A@mail.gmail.com>
Date:	Tue, 19 Aug 2014 22:26:12 +0200
From:	Richard Weinberger <richard.weinberger@...il.com>
To:	Thomas Meyer <thomas@...3r.de>
Cc:	Valdis Kletnieks <Valdis.Kletnieks@...edu>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux@...rsten-knabe.de
Subject: Re: [UML] 3.16 build without optimization fails

On Tue, Aug 19, 2014 at 10:19 PM, Thomas Meyer <thomas@...3r.de> wrote:
> Hi.
>
> Thanks for your answer.
>
> There goes my plan to better understand an UML kernel lock up by using a debugger... Everything gets optimised out with -O2 :-(

Is it the filesystem/block lockup you saw some time ago?
Maybe Thorsten can give more details.
He sent me an patch off list a few days ago.

> Can you give an example function that relies on this GCC feature?
>
> With kind regards
> Thomas
>
> Am 19.08.2014 22:06 schrieb Valdis.Kletnieks@...edu:
>>
>> On Tue, 19 Aug 2014 21:12:10 +0200, Thomas Meyer said:
>> > > Hi,
>> > >
>> > > the build with -O0 fails with:
>>
>> > > bug or feature?
>> > >
>> > > any ideas?
>>
>> Feature.  The kernel is *known* to not build with -O0, because that
>> disables *all* function inlining, and there's several functions that *have*
>> to be inlined in order to function properly (most notably, anything
>> that uses the gcc __builtin_return_address in a function that is expected
>> to be inlined).



-- 
Thanks,
//richard
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