lib/ringbuffer/vatomic.h

   1 #ifndef _LIB_RING_BUFFER_VATOMIC_H
   2 #define _LIB_RING_BUFFER_VATOMIC_H
   3
   4 /*
   5  * lib/ringbuffer/vatomic.h
   6  *
   7  * Copyright (C) 2010-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   8  *
   9  * This library is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU Lesser General Public
  11  * License as published by the Free Software Foundation; only
  12  * version 2.1 of the License.
  13  *
  14  * This library is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  17  * Lesser General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU Lesser General Public
  20  * License along with this library; if not, write to the Free Software
  21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  22  */
  23
  24 #include <asm/atomic.h>
  25 #include <asm/local.h>
  26
  27 /*
  28  * Same data type (long) accessed differently depending on configuration.
  29  * v field is for non-atomic access (protected by mutual exclusion).
  30  * In the fast-path, the ring_buffer_config structure is constant, so the
  31  * compiler can statically select the appropriate branch.
  32  * local_t is used for per-cpu and per-thread buffers.
  33  * atomic_long_t is used for globally shared buffers.
  34  */
  35 union v_atomic {
  36         local_t l;
  37         atomic_long_t a;
  38         long v;
  39 };
  40
  41 static inline
  42 long v_read(const struct lib_ring_buffer_config *config, union v_atomic *v_a)
  43 {
  44         if (config->sync == RING_BUFFER_SYNC_PER_CPU)
  45                 return local_read(&v_a->l);
  46         else
  47                 return atomic_long_read(&v_a->a);
  48 }
  49
  50 static inline
  51 void v_set(const struct lib_ring_buffer_config *config, union v_atomic *v_a,
  52            long v)
  53 {
  54         if (config->sync == RING_BUFFER_SYNC_PER_CPU)
  55                 local_set(&v_a->l, v);
  56         else
  57                 atomic_long_set(&v_a->a, v);
  58 }
  59
  60 static inline
  61 void v_add(const struct lib_ring_buffer_config *config, long v, union v_atomic *v_a)
  62 {
  63         if (config->sync == RING_BUFFER_SYNC_PER_CPU)
  64                 local_add(v, &v_a->l);
  65         else
  66                 atomic_long_add(v, &v_a->a);
  67 }
  68
  69 static inline
  70 void v_inc(const struct lib_ring_buffer_config *config, union v_atomic *v_a)
  71 {
  72         if (config->sync == RING_BUFFER_SYNC_PER_CPU)
  73                 local_inc(&v_a->l);
  74         else
  75                 atomic_long_inc(&v_a->a);
  76 }
  77
  78 /*
  79  * Non-atomic decrement. Only used by reader, apply to reader-owned subbuffer.
  80  */
  81 static inline
  82 void _v_dec(const struct lib_ring_buffer_config *config, union v_atomic *v_a)
  83 {
  84         --v_a->v;
  85 }
  86
  87 static inline
  88 long v_cmpxchg(const struct lib_ring_buffer_config *config, union v_atomic *v_a,
  89                long old, long _new)
  90 {
  91         if (config->sync == RING_BUFFER_SYNC_PER_CPU)
  92                 return local_cmpxchg(&v_a->l, old, _new);
  93         else
  94                 return atomic_long_cmpxchg(&v_a->a, old, _new);
  95 }
  96
  97 #endif /* _LIB_RING_BUFFER_VATOMIC_H */