diff options
Diffstat (limited to 'include/linux/compiler.h')
| -rw-r--r-- | include/linux/compiler.h | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 867722591be2..5d66777914db 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -252,6 +252,22 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s #define WRITE_ONCE(x, val) \ ({ typeof(x) __val = (val); __write_once_size(&(x), &__val, sizeof(__val)); __val; }) +/** + * READ_ONCE_CTRL - Read a value heading a control dependency + * @x: The value to be read, heading the control dependency + * + * Control dependencies are tricky. See Documentation/memory-barriers.txt + * for important information on how to use them. Note that in many cases, + * use of smp_load_acquire() will be much simpler. Control dependencies + * should be avoided except on the hottest of hotpaths. + */ +#define READ_ONCE_CTRL(x) \ +({ \ + typeof(x) __val = READ_ONCE(x); \ + smp_read_barrier_depends(); /* Enforce control dependency. */ \ + __val; \ +}) + #endif /* __KERNEL__ */ #endif /* __ASSEMBLY__ */ |