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

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Date:	Tue, 19 Aug 2014 22:35:15 +0200
From:	Thomas Meyer <thomas@...3r.de>
To:	Richard Weinberger <richard.weinberger@...il.com>
Cc:	linux@...rsten-knabe.de,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Valdis Kletnieks <Valdis.Kletnieks@...edu>
Subject: Re: [UML] 3.16 build without optimization fails

Yes, it's still there.

Am 19.08.2014 22:26 schrieb Richard Weinberger <richard.weinberger@...il.com>:
>
> 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