Messages in this thread | | | Date | Fri, 28 Jun 2013 17:09:41 +0200 | From | Ralf Baechle <> | Subject | Re: [PATCH] arch: tile: include: asm: add cmpxchg64() definition |
| |
On Fri, Jun 28, 2013 at 09:51:35AM +0800, Chen Gang wrote:
> Need add cmpxchg64(), or will cause compiling issue. > > Just define it as cmpxchg(), since cmpxchg() can support 8 bytes. > > The related error (with allmodconfig): > > drivers/block/blockconsole.c: In function ‘bcon_advance_console_bytes’: > drivers/block/blockconsole.c:164:2: error: implicit declaration of function ‘cmpxchg64’ [-Werror=implicit-function-declaration] > > Signed-off-by: Chen Gang <gang.chen@asianux.com> > --- > arch/tile/include/asm/cmpxchg.h | 2 ++ > 1 files changed, 2 insertions(+), 0 deletions(-) > > diff --git a/arch/tile/include/asm/cmpxchg.h b/arch/tile/include/asm/cmpxchg.h > index 276f067..7688c28 100644 > --- a/arch/tile/include/asm/cmpxchg.h > +++ b/arch/tile/include/asm/cmpxchg.h > @@ -68,6 +68,8 @@ extern unsigned long __cmpxchg_called_with_bad_pointer(void); > > #define tas(ptr) (xchg((ptr), 1)) > > +#define cmpxchg64(ptr, o, n) cmpxchg((ptr), (o), (n))
that's broken. cmpxchg64 is suposed to work on 64 bit operands ONLY. This definition (used by MIPS and Alpha) will work properly:
#define cmpxchg64(ptr, o, n) \ ({ \ BUILD_BUG_ON(sizeof(*(ptr)) != 8); \ cmpxchg((ptr), (o), (n)); \ })
This should cure blockconsole on Tile but not on MIPS.
struct blockconsole { ... u64 console_bytes; ... };
static void bcon_advance_console_bytes(struct blockconsole *bc, int bytes) { u64 old, new; ... } while (cmpxchg64(&bc->console_bytes, old, new) != old); }
So it's using cmpxchg64() to operate on 64 bit objects - but that's not going to work on every architecture. Many 32 bit architectures only provide atomic operations that operate on 32 bit quantities.
Ralf -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |