hc
2024-12-19 9370bb92b2d16684ee45cf24e879c93c509162da
kernel/arch/alpha/include/asm/barrier.h
....@@ -2,64 +2,15 @@
22 #ifndef __BARRIER_H
33 #define __BARRIER_H
44
5
-#include <asm/compiler.h>
6
-
75 #define mb() __asm__ __volatile__("mb": : :"memory")
86 #define rmb() __asm__ __volatile__("mb": : :"memory")
97 #define wmb() __asm__ __volatile__("wmb": : :"memory")
108
11
-/**
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- * read_barrier_depends - Flush all pending reads that subsequents reads
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- * depend on.
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- *
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- * No data-dependent reads from memory-like regions are ever reordered
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- * over this barrier. All reads preceding this primitive are guaranteed
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- * to access memory (but not necessarily other CPUs' caches) before any
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- * reads following this primitive that depend on the data return by
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- * any of the preceding reads. This primitive is much lighter weight than
20
- * rmb() on most CPUs, and is never heavier weight than is
21
- * rmb().
22
- *
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- * These ordering constraints are respected by both the local CPU
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- * and the compiler.
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- *
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- * Ordering is not guaranteed by anything other than these primitives,
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- * not even by data dependencies. See the documentation for
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- * memory_barrier() for examples and URLs to more information.
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- *
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- * For example, the following code would force ordering (the initial
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- * value of "a" is zero, "b" is one, and "p" is "&a"):
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- *
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- * <programlisting>
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- * CPU 0 CPU 1
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- *
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- * b = 2;
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- * memory_barrier();
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- * p = &b; q = p;
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- * read_barrier_depends();
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- * d = *q;
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- * </programlisting>
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- *
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- * because the read of "*q" depends on the read of "p" and these
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- * two reads are separated by a read_barrier_depends(). However,
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- * the following code, with the same initial values for "a" and "b":
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- *
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- * <programlisting>
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- * CPU 0 CPU 1
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- *
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- * a = 2;
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- * memory_barrier();
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- * b = 3; y = b;
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- * read_barrier_depends();
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- * x = a;
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- * </programlisting>
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- *
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- * does not enforce ordering, since there is no data dependency between
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- * the read of "a" and the read of "b". Therefore, on some CPUs, such
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- * as Alpha, "y" could be set to 3 and "x" to 0. Use rmb()
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- * in cases like this where there are no data dependencies.
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- */
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-#define read_barrier_depends() __asm__ __volatile__("mb": : :"memory")
9
+#define __smp_load_acquire(p) \
10
+({ \
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+ compiletime_assert_atomic_type(*p); \
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+ __READ_ONCE(*p); \
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+})
6314
6415 #ifdef CONFIG_SMP
6516 #define __ASM_SMP_MB "\tmb\n"