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authorWill Deacon <will@kernel.org>2019-10-16 02:29:32 +0300
committerWill Deacon <will@kernel.org>2020-07-21 12:50:35 +0300
commite506ea451254ab17e0bf918ca36232fec2a9b10c (patch)
tree3ed1c29d46b626eb36ffd8f055e0b74c864e31ab /include/linux/compiler.h
parentf143c11bb7b924403ea2d5b5c990717772293620 (diff)
downloadlinux-e506ea451254ab17e0bf918ca36232fec2a9b10c.tar.xz
compiler.h: Split {READ,WRITE}_ONCE definitions out into rwonce.h
In preparation for allowing architectures to define their own implementation of the READ_ONCE() macro, move the generic {READ,WRITE}_ONCE() definitions out of the unwieldy 'linux/compiler.h' file and into a new 'rwonce.h' header under 'asm-generic'. Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Will Deacon <will@kernel.org>
Diffstat (limited to 'include/linux/compiler.h')
-rw-r--r--include/linux/compiler.h93
1 files changed, 2 insertions, 91 deletions
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 204e76856435..f075a3df4fe2 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -230,28 +230,6 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
# define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__)
#endif
-/*
- * Prevent the compiler from merging or refetching reads or writes. The
- * compiler is also forbidden from reordering successive instances of
- * READ_ONCE and WRITE_ONCE, but only when the compiler is aware of some
- * particular ordering. One way to make the compiler aware of ordering is to
- * put the two invocations of READ_ONCE or WRITE_ONCE in different C
- * statements.
- *
- * These two macros will also work on aggregate data types like structs or
- * unions.
- *
- * Their two major use cases are: (1) Mediating communication between
- * process-level code and irq/NMI handlers, all running on the same CPU,
- * and (2) Ensuring that the compiler does not fold, spindle, or otherwise
- * mutilate accesses that either do not require ordering or that interact
- * with an explicit memory barrier or atomic instruction that provides the
- * required ordering.
- */
-#include <asm/barrier.h>
-#include <linux/kasan-checks.h>
-#include <linux/kcsan-checks.h>
-
/**
* data_race - mark an expression as containing intentional data races
*
@@ -272,65 +250,6 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
__v; \
})
-/*
- * Use __READ_ONCE() instead of READ_ONCE() if you do not require any
- * atomicity or dependency ordering guarantees. Note that this may result
- * in tears!
- */
-#define __READ_ONCE(x) (*(const volatile __unqual_scalar_typeof(x) *)&(x))
-
-#define __READ_ONCE_SCALAR(x) \
-({ \
- __unqual_scalar_typeof(x) __x = __READ_ONCE(x); \
- smp_read_barrier_depends(); \
- (typeof(x))__x; \
-})
-
-#define READ_ONCE(x) \
-({ \
- compiletime_assert_rwonce_type(x); \
- __READ_ONCE_SCALAR(x); \
-})
-
-#define __WRITE_ONCE(x, val) \
-do { \
- *(volatile typeof(x) *)&(x) = (val); \
-} while (0)
-
-#define WRITE_ONCE(x, val) \
-do { \
- compiletime_assert_rwonce_type(x); \
- __WRITE_ONCE(x, val); \
-} while (0)
-
-static __no_sanitize_or_inline
-unsigned long __read_once_word_nocheck(const void *addr)
-{
- return __READ_ONCE(*(unsigned long *)addr);
-}
-
-/*
- * Use READ_ONCE_NOCHECK() instead of READ_ONCE() if you need to load a
- * word from memory atomically but without telling KASAN/KCSAN. This is
- * usually used by unwinding code when walking the stack of a running process.
- */
-#define READ_ONCE_NOCHECK(x) \
-({ \
- unsigned long __x; \
- compiletime_assert(sizeof(x) == sizeof(__x), \
- "Unsupported access size for READ_ONCE_NOCHECK()."); \
- __x = __read_once_word_nocheck(&(x)); \
- smp_read_barrier_depends(); \
- (typeof(x))__x; \
-})
-
-static __no_kasan_or_inline
-unsigned long read_word_at_a_time(const void *addr)
-{
- kasan_check_read(addr, 1);
- return *(unsigned long *)addr;
-}
-
#endif /* __KERNEL__ */
/*
@@ -395,16 +314,6 @@ static inline void *offset_to_ptr(const int *off)
compiletime_assert(__native_word(t), \
"Need native word sized stores/loads for atomicity.")
-/*
- * Yes, this permits 64-bit accesses on 32-bit architectures. These will
- * actually be atomic in some cases (namely Armv7 + LPAE), but for others we
- * rely on the access being split into 2x32-bit accesses for a 32-bit quantity
- * (e.g. a virtual address) and a strong prevailing wind.
- */
-#define compiletime_assert_rwonce_type(t) \
- compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \
- "Unsupported access size for {READ,WRITE}_ONCE().")
-
/* &a[0] degrades to a pointer: a different type from an array */
#define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
@@ -414,4 +323,6 @@ static inline void *offset_to_ptr(const int *off)
*/
#define prevent_tail_call_optimization() mb()
+#include <asm/rwonce.h>
+
#endif /* __LINUX_COMPILER_H */