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author | Russell King <rmk+kernel@arm.linux.org.uk> | 2015-07-07 12:35:33 +0100 |
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committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2015-07-07 12:35:33 +0100 |
commit | 06be5eefe1192eb8ce8d07497f67595b6bfe9741 (patch) | |
tree | 80f1987d4970f8079681f8be0c135cafc8d6329a /include/linux/compiler.h | |
parent | ARM: fix lockdep unannotated irqs-off warning (diff) | |
parent | ARM: avoid unwanted GCC memset()/memcpy() optimisations for IO variants (diff) | |
download | linux-dev-06be5eefe1192eb8ce8d07497f67595b6bfe9741.tar.xz linux-dev-06be5eefe1192eb8ce8d07497f67595b6bfe9741.zip |
Merge branches 'fixes' and 'ioremap' into for-linus
Diffstat (limited to 'include/linux/compiler.h')
-rw-r--r-- | include/linux/compiler.h | 22 |
1 files changed, 20 insertions, 2 deletions
diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 867722591be2..26fc8bc77f85 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -21,6 +21,7 @@ # define __rcu __attribute__((noderef, address_space(4))) #else # define __rcu +# define __pmem __attribute__((noderef, address_space(5))) #endif extern void __chk_user_ptr(const volatile void __user *); extern void __chk_io_ptr(const volatile void __iomem *); @@ -42,6 +43,7 @@ extern void __chk_io_ptr(const volatile void __iomem *); # define __cond_lock(x,c) (c) # define __percpu # define __rcu +# define __pmem #endif /* Indirect macros required for expanded argument pasting, eg. __LINE__. */ @@ -250,7 +252,23 @@ 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; }) + +/** + * 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__ */ @@ -450,7 +468,7 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s * with an explicit memory barrier or atomic instruction that provides the * required ordering. * - * If possible use READ_ONCE/ASSIGN_ONCE instead. + * If possible use READ_ONCE()/WRITE_ONCE() instead. */ #define __ACCESS_ONCE(x) ({ \ __maybe_unused typeof(x) __var = (__force typeof(x)) 0; \ |