linux-kernel - Re: [PATCH] sparc: mark __arch_xchg() as __always

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Message-ID: <20230628155103.GA214400@ravnborg.org>
Date:   Wed, 28 Jun 2023 17:51:03 +0200
From:   Sam Ravnborg <sam@...nborg.org>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Kees Cook <keescook@...omium.org>,
        Mark Rutland <mark.rutland@....com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Arnd Bergmann <arnd@...db.de>,
        Guenter Roeck <linux@...ck-us.net>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Ingo Molnar <mingo@...nel.org>,
        Andi Shyti <andi.shyti@...ux.intel.com>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Palmer Dabbelt <palmer@...osinc.com>,
        sparclinux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sparc: mark __arch_xchg() as __always_inline

On Wed, Jun 28, 2023 at 11:49:18AM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> An otherwise correct change to the atomic operations uncovered an
> existing bug in the sparc __arch_xchg() function, which is calls
> __xchg_called_with_bad_pointer() when its arguments are unknown at
> compile time:
> 
> ERROR: modpost: "__xchg_called_with_bad_pointer" [lib/atomic64_test.ko] undefined!
> 
> This now happens because gcc determines that it's better to not inline the
> function. Avoid this by just marking the function as __always_inline
> to force the compiler to do the right thing here.
> 
> Reported-by: Guenter Roeck <linux@...ck-us.net>
> Link: https://lore.kernel.org/all/c525adc9-6623-4660-8718-e0c9311563b8@roeck-us.net/
> Fixes: d12157efc8e08 ("locking/atomic: make atomic*_{cmp,}xchg optional")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
Reviewed-by: Sam Ravnborg <sam@...nborg.org>

I assume you will find a way to apply the patch.

	Sam