From: Arnd Bergmann <arnd@arndb.de>
To: Marek Vasut <marex@denx.de>
Cc: linux-kernel@vger.kernel.org, lftan@altera.com,
linux-arch@vger.kernel.org,
Russell King <rmk+kernel@arm.linux.org.uk>
Subject: Re: [PATCH] asm-generic: cmpxchg: avoid warnings from macro-ized cmpxchg() implementations
Date: Wed, 14 Oct 2015 17:01:45 +0200 [thread overview]
Message-ID: <50122244.xQZES6VAKE@wuerfel> (raw)
In-Reply-To: <1442637741-10807-1-git-send-email-marex@denx.de>
On Saturday 19 September 2015 06:42:21 Marek Vasut wrote:
> This change is similar to e001bbae7147b111fe1aa42beaf835635f3c016e
> ARM: cmpxchg: avoid warnings from macro-ized cmpxchg() implementations
>
> A recent change in kernel/acct.c added a new warning for many
> configurations using generic __xchg() implementation:
>
> In file included from ./arch/nios2/include/asm/cmpxchg.h:12:0,
> from include/asm-generic/atomic.h:18,
> from arch/nios2/include/generated/asm/atomic.h:1,
> from include/linux/atomic.h:4,
> from include/linux/spinlock.h:406,
> from include/linux/mmzone.h:7,
> from include/linux/gfp.h:5,
> from include/linux/mm.h:9,
> from kernel/acct.c:46:
> kernel/acct.c: In function 'acct_pin_kill':
> include/asm-generic/cmpxchg.h:94:3: warning: value computed is not used [-Wunused-value]
> ((__typeof__(*(ptr)))__cmpxchg_local_generic((ptr), (unsigned long)(o),\
> ^
> include/asm-generic/cmpxchg.h:102:28: note: in expansion of macro 'cmpxchg_local'
> #define cmpxchg(ptr, o, n) cmpxchg_local((ptr), (o), (n))
> ^
> kernel/acct.c:177:2: note: in expansion of macro 'cmpxchg'
> cmpxchg(&acct->ns->bacct, pin, NULL);
> ^
>
> The code is in fact correct, it's just a cmpxchg() call that
> intentionally ignores the result, and no other code does that. The
> warning does not show up on x86 because of the way that its cmpxchg()
> macro is written. This changes the asm-ggeneric implementation to use
> a similar construct with a compound expression instead of a typecast,
> which causes the compiler to not complain about an unused result.
>
> Fix the other macros in this file in a similar way, and place them
> just below their function implementations.
>
> Signed-off-by: Marek Vasut <marex@denx.de>
> Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Applied to my asm-generic tree, thanks!
Arnd
next prev parent reply other threads:[~2015-10-14 15:01 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-19 4:42 Marek Vasut
2015-10-01 14:06 ` Ley Foon Tan
2015-10-14 15:01 ` Arnd Bergmann [this message]
2015-10-15 14:25 ` Marek Vasut
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