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Date:   Thu, 21 May 2020 18:35:22 +0100
From:   Will Deacon <will@kernel.org>
To:     Stephen Rothwell <sfr@canb.auug.org.au>
Cc:     Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Linux Next Mailing List <linux-next@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        elver@google.com, bp@alien8.de
Subject: Re: linux-next: build failure after merge of the tip tree
Message-ID: <20200521173520.GL6608@willie-the-truck>
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Hi Stephen,

[+Marco and Boris]

On Fri, May 22, 2020 at 03:31:19AM +1000, Stephen Rothwell wrote:
> After merging the tip tree, all my linux-next builds took signficantly
> longer and used much more memory.  In some cases, builds would seg fault
> due to running out of memory :-(
> 
> I have eventaully bisected it to commit
> 
>   cdd28ad2d811 ("READ_ONCE: Use data_race() to avoid KCSAN instrumentation")
> 
> For my (e.g.) x86_64 allmodconfig builds (cross compiled on PowerPC le,
> -j80) the elapsed time went from around 9 minutes to over 17 minutes
> and the maximum resident size (as reported by /usr/bin/time) from around
> 500M to around 2G (I saw lots of cc1 processes over 2G in size).
> 
> For tomorrow's linux-next (well, later today :-() I will revert that
> commit (and its child) when I merge the tip tree.

Sorry about that, seems we can't avoid running into compiler problems with
this lot. The good news is that there's a series to fix this here:

https://lore.kernel.org/r/20200521142047.169334-1-elver@google.com

so hopefully this be fixed in -tip soon (but I agree that reverting the
thing in -next in the meantime makes sense).

Will