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Diffstat (limited to 'include/linux/compiler.h')
-rw-r--r--include/linux/compiler.h37
1 files changed, 35 insertions, 2 deletions
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 867722591..e08a6ae7c 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -17,6 +17,7 @@
# define __release(x) __context__(x,-1)
# define __cond_lock(x,c) ((c) ? ({ __acquire(x); 1; }) : 0)
# define __percpu __attribute__((noderef, address_space(3)))
+# define __pmem __attribute__((noderef, address_space(5)))
#ifdef CONFIG_SPARSE_RCU_POINTER
# define __rcu __attribute__((noderef, address_space(4)))
#else
@@ -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__ */
@@ -450,13 +468,28 @@ 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; \
(volatile typeof(x) *)&(x); })
#define ACCESS_ONCE(x) (*__ACCESS_ONCE(x))
+/**
+ * lockless_dereference() - safely load a pointer for later dereference
+ * @p: The pointer to load
+ *
+ * Similar to rcu_dereference(), but for situations where the pointed-to
+ * object's lifetime is managed by something other than RCU. That
+ * "something other" might be reference counting or simple immortality.
+ */
+#define lockless_dereference(p) \
+({ \
+ typeof(p) _________p1 = READ_ONCE(p); \
+ smp_read_barrier_depends(); /* Dependency order vs. p above. */ \
+ (_________p1); \
+})
+
/* Ignore/forbid kprobes attach on very low level functions marked by this attribute: */
#ifdef CONFIG_KPROBES
# define __kprobes __attribute__((__section__(".kprobes.text")))