linux-kernel - Re: mmotm 2020-05-13-20-30 uploaded (objtool warnings)

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Date:   Fri, 29 May 2020 21:08:56 +0100
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Christoph Hellwig <hch@....de>,
        Randy Dunlap <rdunlap@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mark Brown <broonie@...nel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        Linux Next Mailing List <linux-next@...r.kernel.org>,
        Michal Hocko <mhocko@...e.cz>, mm-commits@...r.kernel.org,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        the arch/x86 maintainers <x86@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: mmotm 2020-05-13-20-30 uploaded (objtool warnings)

On Fri, May 29, 2020 at 12:31:04PM -0700, Linus Torvalds wrote:
> On Fri, May 29, 2020 at 9:50 AM Josh Poimboeuf <jpoimboe@...hat.com> wrote:
> >
> > From staring at the asm I think the generated code is correct, it's just
> > that the nested likelys with ftrace profiling cause GCC to converge the
> > error/success paths.  But objtool doesn't do register value tracking so
> > it's not smart enough to know that it's safe.
> 
> I'm surprised that gcc doesn't end up doing the obvious CSE and then
> branch following and folding it all away in the end, but your patch is
> obviously the right thing to do regardless, so ack on that.
> 
> Al - I think this had best go into your uaccess cleanup branch with
> that csum-wrapper update, to avoid any unnecessary conflicts or
> dependencies.

Sure, just let me verify that other branches don't introduce anything
of that sort...