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#ifndef LIBURING_BARRIER_H
#define LIBURING_BARRIER_H
/*
From the kernel documentation file refcount-vs-atomic.rst:
A RELEASE memory ordering guarantees that all prior loads and
stores (all po-earlier instructions) on the same CPU are completed
before the operation. It also guarantees that all po-earlier
stores on the same CPU and all propagated stores from other CPUs
must propagate to all other CPUs before the release operation
(A-cumulative property). This is implemented using
:c:func:`smp_store_release`.
An ACQUIRE memory ordering guarantees that all post loads and
stores (all po-later instructions) on the same CPU are
completed after the acquire operation. It also guarantees that all
po-later stores on the same CPU must propagate to all other CPUs
after the acquire operation executes. This is implemented using
:c:func:`smp_acquire__after_ctrl_dep`.
*/
/* From tools/include/linux/compiler.h */
/* Optimization barrier */
/* The "volatile" is due to gcc bugs */
#define barrier() __asm__ __volatile__("": : :"memory")
/* From tools/virtio/linux/compiler.h */
#define WRITE_ONCE(var, val) \
(*((volatile typeof(val) *)(&(var))) = (val))
#define READ_ONCE(var) (*((volatile typeof(var) *)(&(var))))
#if defined(__x86_64__) || defined(__i386__)
/* From tools/arch/x86/include/asm/barrier.h */
#if defined(__i386__)
/*
* Some non-Intel clones support out of order store. wmb() ceases to be a
* nop for these.
*/
#define mb() asm volatile("lock; addl $0,0(%%esp)" ::: "memory")
#define rmb() asm volatile("lock; addl $0,0(%%esp)" ::: "memory")
#define wmb() asm volatile("lock; addl $0,0(%%esp)" ::: "memory")
#elif defined(__x86_64__)
#define mb() asm volatile("mfence" ::: "memory")
#define rmb() asm volatile("lfence" ::: "memory")
#define wmb() asm volatile("sfence" ::: "memory")
#define smp_rmb() barrier()
#define smp_wmb() barrier()
#define smp_mb() asm volatile("lock; addl $0,-132(%%rsp)" ::: "memory", "cc")
#endif
#if defined(__x86_64__)
#define smp_store_release(p, v) \
do { \
barrier(); \
WRITE_ONCE(*(p), (v)); \
} while (0)
#define smp_load_acquire(p) \
({ \
typeof(*p) ___p1 = READ_ONCE(*(p)); \
barrier(); \
___p1; \
})
#endif /* defined(__x86_64__) */
#else /* defined(__x86_64__) || defined(__i386__) */
/*
* Add arch appropriate definitions. Be safe and use full barriers for
* archs we don't have support for.
*/
#define smp_rmb() __sync_synchronize()
#define smp_wmb() __sync_synchronize()
#endif /* defined(__x86_64__) || defined(__i386__) */
/* From tools/include/asm/barrier.h */
#ifndef smp_store_release
# define smp_store_release(p, v) \
do { \
smp_mb(); \
WRITE_ONCE(*p, v); \
} while (0)
#endif
#ifndef smp_load_acquire
# define smp_load_acquire(p) \
({ \
typeof(*p) ___p1 = READ_ONCE(*p); \
smp_mb(); \
___p1; \
})
#endif
#endif /* defined(LIBURING_BARRIER_H) */
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