linux-kernel - Re: objtool warnings for kernel/trace/trace_selftest

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Date:   Mon, 17 Dec 2018 20:29:38 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     Andi Kleen <ak@...ux.intel.com>, Arnd Bergmann <arnd@...db.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        the arch/x86 maintainers <x86@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Miroslav Benes <mbenes@...e.cz>
Subject: Re: objtool warnings for kernel/trace/trace_selftest_dynamic.o

On Mon, Dec 17, 2018 at 12:16:38PM -0600, Josh Poimboeuf wrote:

> > Yes LTO causes the to be treated like static functions.
> > 
> > I guess noclone is unlikely to be really needed here because these
> > functions are unlikely to be cloned.
> > 
> > So as a workaround it could be removed.
> > 
> > But note we have other noclone functions in the tree (like in KVM)
> > which actually need it.
> 
> How about we just use the __used attribute then?  It seems to have the
> same result of preventing IPA optimizations (without the weird side
> effect of missing frame pointers).

AFAIK we don't have any in-tree LTO, so it can all go in the bin.

When/if we get the LTO trainwreck sorted -- which very much includes
getting that memory-order-consume fixed -- we can revisit all that.