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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Sun, 19 Apr 2020 11:56:51 -0700
Message-ID: <CAHk-=wjUS9b-B1n=OCBdqq3mdVTNGz0zqhGnrtMijoB5qT+96g@mail.gmail.com>
Subject: Re: [GIT pull] perf/urgent for 5.7-rc2
To:     Thomas Gleixner <tglx@linutronix.de>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Masahiro Yamada <masahiroy@kernel.org>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "the arch/x86 maintainers" <x86@kernel.org>
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On Sun, Apr 19, 2020 at 6:57 AM Thomas Gleixner <tglx@linutronix.de> wrote:
>
> please pull the latest perf/urgent branch from:
>
>    git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git perf-urgent-2020-04-19

So this one took me by surprise, because it only touched the 'tools'
subdirectory for the perf tool, and then when I did what I thought
would be a trivial test build, it re-built the whole kernel.

And that made me go "Whaa?!?"

After looking at it for a while (longer than I really want to admit),
I realized that it's because the headers are also shared with objtool,
and it all kind of made sense.

I say "kind of" because I would have wished that objtool wouldn't
necessarily rebuild everything.

So I'm wondering if there any way that objtool could be run at
link-time (and archive time) rather than force a re-build of all the
object files from source?

This is not a huge deal, it's not like the occasional full rebuild is
_that_ big of a problem, but since I was surprised, I thought I'd
ask..

              Linus