On Mon, May 11, 2015 at 04:54:08PM +0200, Peter Zijlstra wrote:
> +++ b/arch/arm/include/asm/barrier.h
> @@ -81,7 +81,7 @@ do { \
> #define read_barrier_depends() do { } while(0)
> #define smp_read_barrier_depends() do { } while(0)
>
> -#define set_mb(var, value) do { var = value; smp_mb(); } while (0)
> +#define set_mb(var, value) do { WRITE_ONCE(var, value); smp_mb(); } while (0)
>
> #define smp_mb__before_atomic() smp_mb()
> #define smp_mb__after_atomic() smp_mb()
Which triggered a massive compile fail and requires the same union
trickery we already had for READ_ONCE().
Added the below bit to the patch to aid compiling.
---
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index a7c0941d10da..03e227ba481c 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -250,7 +250,7 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
({ union { typeof(x) __val; char __c[1]; } __u; __read_once_size(&(x), __u.__c, sizeof(x)); __u.__val; })
#define WRITE_ONCE(x, val) \
- ({ typeof(x) __val = (val); __write_once_size(&(x), &__val, sizeof(__val)); __val; })
+ ({ union { typeof(x) __val; char __c[1]; } __u = { .__val = (val) }; __write_once_size(&(x), __u.__c, sizeof(x)); __u.__val; })
#endif /* __KERNEL__ */
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