linux-kernel - Re: [PATCH] x86/asm: Fix inline asm call constraints for GCC 4.4

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Date:   Fri, 29 Sep 2017 09:51:30 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>,
        the arch/x86 maintainers <x86@...nel.org>,
        kernel test robot <xiaolong.ye@...el.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Matthias Kaehlcke <mka@...omium.org>,
        Alexander Potapenko <glider@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Dmitriy Vyukov <dvyukov@...gle.com>,
        Miguel Bernal Marin <miguel.bernal.marin@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>, LKP <lkp@...org>
Subject: Re: [PATCH] x86/asm: Fix inline asm call constraints for GCC 4.4


* Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> On Thu, Sep 28, 2017 at 2:58 PM, Josh Poimboeuf <jpoimboe@...hat.com> wrote:
> >
> > Reported-by: kernel test robot <xiaolong.ye@...el.com>
> > Fixes: f5caf621ee35 ("x86/asm: Fix inline asm call constraints for Clang")
> > Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
> 
> Side note: it's not like I personally need the credit, but in general
> I really want people to pick up on who debugged the code and pointed
> to the solution. That's often more of the work than the fix itself.
> 
> The kernel test robot report looked to be ignored as a "gcc-4.4 is too
> old to worry about" thing. [...]

No, and sorry if my first reply grumbling about how old GCC 4.4 is sounded that 
way! We have to live with compiler bugs no matter how old the compiler is, the 
release cycles are decoupled to such a degree and external tooling propagates with 
such high latencies that that's the only sane thing to do.

We also officially support GCC 3.2 and later compilers. Had this regression not 
been resolved within a week or so I was fully ready to queue up a revert commit, 
no questions asked.

Plus it's not just that it's a regression, but adding support for a different 
compiler is about the _worst_ possible reason to break working compilers ...

> [...] People who then step up and analyze the problem are rare as it is. They 
> need to be credited in the commit logs.
> 
> We don't have any fixed format for that, but it's pretty free-form. So
> we have tags like
> 
>   Root-caused-by:
>   Diagnosed-by:
>   Analyzed-by:
>   Debugged-by:
>   Bisected-by:
>   Fix-suggested-by:
> 
> etc for giving credit to people who figured out some part of a bug
> (and, having grepped for this, we also a _shitload_ of miss-spellings
> of various things ;)

Yeah, I sometimes add such tags, but not routinely. I'll lower the threshold for 
adding such tags, to create further incentives for people to help debug crashes.

Thanks,

	Ingo