Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Mon, 20 Apr 2020 14:36:12 -0500
From:   Josh Poimboeuf <jpoimboe@redhat.com>
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        the arch/x86 maintainers <x86@kernel.org>
Subject: Re: [GIT pull] perf/urgent for 5.7-rc2
Message-ID: <20200420193612.4nv5i62onae6smv2@treble>
References: <158730459860.31269.9496277256253823777.tglx@nanos.tec.linutronix.de>
 <158730460101.31269.5005570498545135614.tglx@nanos.tec.linutronix.de>
 <CAHk-=wjUS9b-B1n=OCBdqq3mdVTNGz0zqhGnrtMijoB5qT+96g@mail.gmail.com>
 <20200419200758.3xry3vn2a5caxapx@treble>
 <20200420074845.GA72554@gmail.com>
 <CAHk-=wiG=Bz57AUmbTyZYMKU6C+nZpS8P2=vFf5xAAhBzrPuTQ@mail.gmail.com>
 <20200420174031.GM20730@hirez.programming.kicks-ass.net>
 <20200420181730.4bmggezf2zhu4ffb@treble>
 <CAHk-=wg6QqiaLqk19nLLAjLFNf8eY7d1m2-Qigg9w3H6iGu+EQ@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
In-Reply-To: <CAHk-=wg6QqiaLqk19nLLAjLFNf8eY7d1m2-Qigg9w3H6iGu+EQ@mail.gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Mon, Apr 20, 2020 at 12:21:46PM -0700, Linus Torvalds wrote:
> On Mon, Apr 20, 2020 at 11:17 AM Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> >
> > If you added something bad to a file, and just rebuilt that file, you
> > wouldn't see the objtool warning until later when you build the entire
> > kernel.
> 
> Yes, that's not optimal, but I think I'd personally still prefer that
> behavior. Especially since I seldom build single files, and in fact
> rather seldom build without some "make -j32" or similar: so build
> errors don't happen linearly in the first place.
> 
> > (Of course the same complaint would apply to vmlinux.o
> > validation.)  But the warning shows the .o file, which could be
> > confusing.
> 
> The warning should show the proper loe-level *.o file, so I don't see
> what's confusing about that.
> 
> Yes, the error would happen while trying to link (say)
> kernel/built-in.a, and 'make' would report that creating that archive
> had failed, but 'objtool' itself would report the particular object
> file it was working on that had issues.

My workflow is often

  $ vi kernel/livepatch/core.c
  $ make kernel/livepatch/core.o

That way I don't have to wait to see what I broke (compile or objtool).

And if whatever I changed was in response to an objtool warning for
kernel/livepatch/core.o, and the warning didn't show up after doing the
above, I might stupidly assume I fixed it.

That's what I meant about it being confusing.  Maybe that's just me
though.

> So the errors should be pretty obvious. But like PeterZ, the makefile
> magic escapes me.

Ditto...

-- 
Josh