linux-kernel - Re: [PATCH -next] x86/mm/pat: silence a data race in cpa_4k

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Date:   Tue, 21 Jan 2020 10:50:56 -0500
From:   Qian Cai <cai@....pw>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Marco Elver <elver@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        the arch/x86 maintainers <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -next] x86/mm/pat: silence a data race in cpa_4k_install



> On Jan 21, 2020, at 10:45 AM, Borislav Petkov <bp@...en8.de> wrote:
> 
> Perhaps because you've been dealing with KCSAN for so long. :-)
> 
> The main angle here, IMO, is that this "fix" is being done solely for
> KCSAN. Or is there another reason to "fix" intentional data races? At
> least I don't see one. And the text says
> 
> "This will generate a lot of noise on a debug kernel with
> debug_pagealloc with KCSAN enabled which could render the system
> unusable."
> 
> So yes, I think it should say something about making KCSAN happy.
> 
> Oh, and while at it I'd prefer it if it did the __no_kcsan function
> annotation instead of the data_race() thing.

Or the patch title could be “play KCSAN well with debug_pagealloc”?

I am fine with __no_kcsan as well. I just need to retest the whole thing first.