lkml.org 
[lkml]   [2015]   [Jun]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH] ARM: avoid cmpxchg warning in kernel/acct.c
From
On Tue, May 12, 2015 at 11:29 PM, Arnd Bergmann <arnd@arndb.de> wrote:
> A recent change in kernel/acct.c added a new warning for many
> configurations on ARM:
>
> kernel/acct.c: In function 'acct_pin_kill':
> arch/arm/include/asm/cmpxchg.h:122:3: warning: value computed is not used [-Wunused-value]
> ((__typeof__(*(ptr)))__cmpxchg_local_generic((ptr), (unsigned long)(o),\
>
> 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 ARM 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.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> Fixes: 3b994d98a815 ("get rid of the second argument of acct_kill()")
> ---
> This helps build some of the ARM defconfigs without warnings once more.
>
> diff --git a/arch/arm/include/asm/cmpxchg.h b/arch/arm/include/asm/cmpxchg.h
> index abb2c3769b01..04be894f7c4e 100644
> --- a/arch/arm/include/asm/cmpxchg.h
> +++ b/arch/arm/include/asm/cmpxchg.h
> @@ -119,8 +119,8 @@ static inline unsigned long __xchg(unsigned long x, volatile void *ptr, int size
> * them available.
> */
> #define cmpxchg_local(ptr, o, n) \
> - ((__typeof__(*(ptr)))__cmpxchg_local_generic((ptr), (unsigned long)(o),\
> - (unsigned long)(n), sizeof(*(ptr))))
> + ({(__typeof__(*(ptr)))__cmpxchg_local_generic((ptr), (unsigned long)(o),\
> + (unsigned long)(n), sizeof(*(ptr)));})
> #define cmpxchg64_local(ptr, o, n) __cmpxchg64_local_generic((ptr), (o), (n))
>
> #ifndef CONFIG_SMP
> @@ -202,10 +202,10 @@ static inline unsigned long __cmpxchg_mb(volatile void *ptr, unsigned long old,
> }
>
> #define cmpxchg(ptr,o,n) \
> - ((__typeof__(*(ptr)))__cmpxchg_mb((ptr), \
> + ({(__typeof__(*(ptr)))__cmpxchg_mb((ptr), \
> (unsigned long)(o), \
> (unsigned long)(n), \
> - sizeof(*(ptr))))
> + sizeof(*(ptr)));})
>
> static inline unsigned long __cmpxchg_local(volatile void *ptr,
> unsigned long old,
>
>

Works for me.

Thanks,
Frans


\
 
 \ /
  Last update: 2015-06-02 12:01    [W:0.039 / U:0.572 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site