在 2016/11/25 11:07, Michael Ellerman 写道:
In commit d0563a1297e2 ("powerpc: Implement {cmp}xchg for u8 and u16")
we removed the volatile from __cmpxchg().
This is leading to warnings such as:
drivers/gpu/drm/drm_lock.c: In function ‘drm_lock_take’:
arch/powerpc/include/asm/cmpxchg.h:484:37: warning: passing argument 1
of ‘__cmpxchg’ discards ‘volatile’ qualifier from pointer target
(__typeof__(*(ptr))) __cmpxchg((ptr), (unsigned long)_o_, \
There doesn't seem to be consensus across architectures whether the
argument is volatile or not, so at least for now put the volatile back.
Fixes: d0563a1297e2 ("powerpc: Implement {cmp}xchg for u8 and u16")
Signed-off-by: Michael Ellerman <m...@ellerman.id.au>
---
Hi, mpe
We implement __cmpxchg in asm so volatile maybe is not needed I think.
But seems compiler is not happy :(
I am okay with your patch. thanks!
arch/powerpc/include/asm/cmpxchg.h | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/include/asm/cmpxchg.h
b/arch/powerpc/include/asm/cmpxchg.h
index c12f110261b2..fc46b664c49e 100644
--- a/arch/powerpc/include/asm/cmpxchg.h
+++ b/arch/powerpc/include/asm/cmpxchg.h
@@ -14,7 +14,7 @@
#endif
#define XCHG_GEN(type, sfx, cl) \
-static inline u32 __xchg_##type##sfx(void *p, u32 val) \
+static inline u32 __xchg_##type##sfx(volatile void *p, u32 val) \
{ \
unsigned int prev, prev_mask, tmp, bitoff, off; \
\
@@ -40,7 +40,7 @@ static inline u32 __xchg_##type##sfx(void *p, u32 val)
\
#define CMPXCHG_GEN(type, sfx, br, br2, cl) \
static inline \
-u32 __cmpxchg_##type##sfx(void *p, u32 old, u32 new) \
+u32 __cmpxchg_##type##sfx(volatile void *p, u32 old, u32 new) \
{ \
unsigned int prev, prev_mask, tmp, bitoff, off; \
\
@@ -399,7 +399,7 @@ __cmpxchg_u64_acquire(u64 *p, unsigned long old, unsigned
long new)
#endif
static __always_inline unsigned long
-__cmpxchg(void *ptr, unsigned long old, unsigned long new,
+__cmpxchg(volatile void *ptr, unsigned long old, unsigned long new,
unsigned int size)
{
switch (size) {
