From: Peter Zijlstra <peterz@infradead.org>
To: Andi Kleen <ak@linux.intel.com>
Cc: linux-kernel@vger.kernel.org, Andi Kleen <andi@firstfloor.org>,
linux-toolchains@vger.kernel.org
Subject: Re: [PATCH] sched: Work around undefined behavior in sched class checking
Date: Wed, 5 May 2021 08:46:19 +0200 [thread overview]
Message-ID: <YJI/OwoflyY2IXvf@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20210505033945.1282851-1-ak@linux.intel.com>
On Tue, May 04, 2021 at 08:39:45PM -0700, Andi Kleen wrote:
> From: Andi Kleen <andi@firstfloor.org>
>
> The scheduler initialization code checks that the scheduling
> classes are consecutive in memory by comparing the end
> addresses with the next address.
>
> Technically in ISO C comparing symbol addresseses outside different objects
> is undefined. With LTO gcc 10 tries to exploits this and creates an
> unconditional BUG_ON in the scheduler initialization, resulting
> in a boot hang.
>
> Use RELOC_HIDE to make this work. This hides the symbols from gcc,
> so the optimizer won't make these assumption. I also split
> the BUG_ONs in multiple.
Urgh, that insanity again :/ Can't we pretty please get a GCC flag to
disable that?
next parent reply other threads:[~2021-05-05 6:46 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20210505033945.1282851-1-ak@linux.intel.com>
2021-05-05 6:46 ` Peter Zijlstra [this message]
2021-05-05 8:47 ` [PATCH] sched: Work around undefined behavior in sched class checking Florian Weimer
2021-05-05 9:04 ` Peter Zijlstra
2021-05-05 14:39 ` Andi Kleen
2021-05-05 16:41 ` Nick Desaulniers
2021-05-05 16:48 ` Andi Kleen
2021-05-05 17:08 ` Nick Desaulniers
2021-05-05 17:20 ` Andi Kleen
2021-05-05 14:34 ` Andi Kleen
2021-05-05 15:34 ` Peter Zijlstra
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