diff options
| author | Will Deacon <will.deacon@arm.com> | 2014-04-30 16:23:06 +0100 |
|---|---|---|
| committer | Jiri Slaby <jslaby@suse.cz> | 2015-06-23 19:13:20 +0200 |
| commit | 75ef6b494a114fe86ea0f1d17d1d6f6eaa60af55 (patch) | |
| tree | 7a70c68d5d4f4d27eb7065b4b1029d18285d8ca4 | |
| parent | f0e943882cea7c762f8a205f8e4b65483ff1898b (diff) | |
| download | lwn-75ef6b494a114fe86ea0f1d17d1d6f6eaa60af55.tar.gz lwn-75ef6b494a114fe86ea0f1d17d1d6f6eaa60af55.zip | |
arm64: xchg: prevent warning if return value is unused
commit e1dfda9ced9bea1413a736f0d578f8218a7788ec upstream.
Some users of xchg() don't bother using the return value, which results
in a compiler warning like the following (from kgdb):
In file included from linux/arch/arm64/include/asm/atomic.h:27:0,
from include/linux/atomic.h:4,
from include/linux/spinlock.h:402,
from include/linux/seqlock.h:35,
from include/linux/time.h:5,
from include/uapi/linux/timex.h:56,
from include/linux/timex.h:56,
from include/linux/sched.h:19,
from include/linux/pid_namespace.h:4,
from kernel/debug/debug_core.c:30:
kernel/debug/debug_core.c: In function ‘kgdb_cpu_enter’:
linux/arch/arm64/include/asm/cmpxchg.h:75:3: warning: value computed is not used [-Wunused-value]
((__typeof__(*(ptr)))__xchg((unsigned long)(x),(ptr),sizeof(*(ptr))))
^
linux/arch/arm64/include/asm/atomic.h:132:30: note: in expansion of macro ‘xchg’
#define atomic_xchg(v, new) (xchg(&((v)->counter), new))
kernel/debug/debug_core.c:504:4: note: in expansion of macro ‘atomic_xchg’
atomic_xchg(&kgdb_active, cpu);
^
This patch makes use of the same trick as we do for cmpxchg, by assigning
the return value to a dummy variable in the xchg() macro itself.
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
| -rw-r--r-- | arch/arm64/include/asm/cmpxchg.h | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/arch/arm64/include/asm/cmpxchg.h b/arch/arm64/include/asm/cmpxchg.h index 8a8ce0e73a38..7b4aaf067a48 100644 --- a/arch/arm64/include/asm/cmpxchg.h +++ b/arch/arm64/include/asm/cmpxchg.h @@ -71,7 +71,12 @@ static inline unsigned long __xchg(unsigned long x, volatile void *ptr, int size } #define xchg(ptr,x) \ - ((__typeof__(*(ptr)))__xchg((unsigned long)(x),(ptr),sizeof(*(ptr)))) +({ \ + __typeof__(*(ptr)) __ret; \ + __ret = (__typeof__(*(ptr))) \ + __xchg((unsigned long)(x), (ptr), sizeof(*(ptr))); \ + __ret; \ +}) static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old, unsigned long new, int size) |