include/ringbuffer/vatomic.h

   1 /* SPDX-License-Identifier: (GPL-2.0-only OR LGPL-2.1-only)
   2  *
   3  * ringbuffer/vatomic.h
   4  *
   5  * Copyright (C) 2010-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   6  */
   7
   8 #ifndef _LIB_RING_BUFFER_VATOMIC_H
   9 #define _LIB_RING_BUFFER_VATOMIC_H
  10
  11 #include <asm/atomic.h>
  12 #include <asm/local.h>
  13
  14 /*
  15  * Same data type (long) accessed differently depending on configuration.
  16  * v field is for non-atomic access (protected by mutual exclusion).
  17  * In the fast-path, the ring_buffer_config structure is constant, so the
  18  * compiler can statically select the appropriate branch.
  19  * local_t is used for per-cpu and per-thread buffers.
  20  * atomic_long_t is used for globally shared buffers.
  21  */
  22 union v_atomic {
  23         local_t l;
  24         atomic_long_t a;
  25         long v;
  26 };
  27
  28 static inline
  29 long v_read(const struct lib_ring_buffer_config *config, union v_atomic *v_a)
  30 {
  31         if (config->sync == RING_BUFFER_SYNC_PER_CPU)
  32                 return local_read(&v_a->l);
  33         else
  34                 return atomic_long_read(&v_a->a);
  35 }
  36
  37 static inline
  38 void v_set(const struct lib_ring_buffer_config *config, union v_atomic *v_a,
  39            long v)
  40 {
  41         if (config->sync == RING_BUFFER_SYNC_PER_CPU)
  42                 local_set(&v_a->l, v);
  43         else
  44                 atomic_long_set(&v_a->a, v);
  45 }
  46
  47 static inline
  48 void v_add(const struct lib_ring_buffer_config *config, long v, union v_atomic *v_a)
  49 {
  50         if (config->sync == RING_BUFFER_SYNC_PER_CPU)
  51                 local_add(v, &v_a->l);
  52         else
  53                 atomic_long_add(v, &v_a->a);
  54 }
  55
  56 static inline
  57 void v_inc(const struct lib_ring_buffer_config *config, union v_atomic *v_a)
  58 {
  59         if (config->sync == RING_BUFFER_SYNC_PER_CPU)
  60                 local_inc(&v_a->l);
  61         else
  62                 atomic_long_inc(&v_a->a);
  63 }
  64
  65 /*
  66  * Non-atomic decrement. Only used by reader, apply to reader-owned subbuffer.
  67  */
  68 static inline
  69 void _v_dec(const struct lib_ring_buffer_config *config, union v_atomic *v_a)
  70 {
  71         --v_a->v;
  72 }
  73
  74 static inline
  75 long v_cmpxchg(const struct lib_ring_buffer_config *config, union v_atomic *v_a,
  76                long old, long _new)
  77 {
  78         if (config->sync == RING_BUFFER_SYNC_PER_CPU)
  79                 return local_cmpxchg(&v_a->l, old, _new);
  80         else
  81                 return atomic_long_cmpxchg(&v_a->a, old, _new);
  82 }
  83
  84 #endif /* _LIB_RING_BUFFER_VATOMIC_H */