linux-kernel - Re: [PATCH] arm64: make atomic helpers __always

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Message-ID: <20210108093258.GB4031@willie-the-truck>
Date:   Fri, 8 Jan 2021 09:32:58 +0000
From:   Will Deacon <will@...nel.org>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Nathan Chancellor <natechancellor@...il.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Mark Rutland <mark.rutland@....com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-arch@...r.kernel.org, clang-built-linux@...glegroups.com
Subject: Re: [PATCH] arm64: make atomic helpers __always_inline

Hi Arnd,

On Fri, Jan 08, 2021 at 10:19:56AM +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> With UBSAN enabled and building with clang, there are occasionally
> warnings like
> 
> WARNING: modpost: vmlinux.o(.text+0xc533ec): Section mismatch in reference from the function arch_atomic64_or() to the variable .init.data:numa_nodes_parsed
> The function arch_atomic64_or() references
> the variable __initdata numa_nodes_parsed.
> This is often because arch_atomic64_or lacks a __initdata
> annotation or the annotation of numa_nodes_parsed is wrong.
> 
> for functions that end up not being inlined as intended but operating
> on __initdata variables. Mark these as __always_inline, along with
> the corresponding asm-generic wrappers.

Hmm, I don't fully grok this. Why does it matter if a non '__init' function
is called with a pointer to some '__initdata'? Or is the reference coming
from somewhere else? (where?).

Will