linux-kernel - Re: CONFIG_VMAP_STACK, on-stack struct, and wake_up

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Message-ID: <20161027191951.zgcrcmvmla7ayeon@pd.tnic>
Date:   Thu, 27 Oct 2016 21:19:51 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Bob Peterson <rpeterso@...hat.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Lutomirski <luto@...capital.net>,
        Andreas Gruenbacher <agruenba@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Steven Whitehouse <swhiteho@...hat.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        linux-mm <linux-mm@...ck.org>
Subject: Re: CONFIG_VMAP_STACK, on-stack struct, and wake_up_bit

On Thu, Oct 27, 2016 at 02:51:30PM -0400, Bob Peterson wrote:
> I couldn't recreate that first boot failure, even using .config.old,
> and even after removing (rm -fR) my linux.git and untarring it from the
> original tarball, doing a make clean, etc.

Hmm, so it could also depend on the randomized offset as it is getting
generated anew each boot. So you could try to boot a couple of times
to see if the randomized offset is generated just right for the bug
condition to match.

I mean, it would be great if you try a couple times but even if you're
unsuccessful, that's fine too - the fix is obviously correct and I've
confirmed that it boots fine in my VM here.

> The output before and after your new patch are the same (except for the times):
> 
> # dmesg | grep -i microcode
> [    5.291679] microcode: microcode updated early to new patch_level=0x010000d9

That looks good.

Thanks!

-- 
Regards/Gruss,
    Boris.

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