linux-kernel - Re: [PATCH 0/7] ARM: hacks for link-time optimization

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Message-ID: <20181217225020.GA16520@hirez.programming.kicks-ass.net>
Date:   Mon, 17 Dec 2018 23:50:20 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Nicolas Pitre <nico@...aro.org>, Andi Kleen <ak@...ux.intel.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Paul McKenney <paulmck@...ux.vnet.ibm.com>,
        Will Deacon <will.deacon@....com>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 0/7] ARM: hacks for link-time optimization

On Tue, Feb 20, 2018 at 10:59:47PM +0100, Arnd Bergmann wrote:
> Hi Nico, all,
> 
> I was playing with ARM link-time optimization handling earlier this
> month, and eventually got it to build cleanly with randconfig kernels,
> but ended up with a lot of ugly hacks to actually pull it off.

How are we dealing with the fact that LTO can break RCU in very subtle
and scary ways?

Do we have a compiler guy on board that has given us a compiler switch
that kills that optimization (and thereby guarantees that behaviour for
future compilers etc..) ?

Also see the thread here:

  https://lkml.kernel.org/r/20171116115810.GH9361@arm.com

(and yes, this is a fine example of how lore sucks for reading email)