src/vppinfra/lock.h

   1 /*
   2  * Copyright (c) 2017 Cisco and/or its affiliates.
   3  * Licensed under the Apache License, Version 2.0 (the "License");
   4  * you may not use this file except in compliance with the License.
   5  * You may obtain a copy of the License at:
   6  *
   7  *     http://www.apache.org/licenses/LICENSE-2.0
   8  *
   9  * Unless required by applicable law or agreed to in writing, software
  10  * distributed under the License is distributed on an "AS IS" BASIS,
  11  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12  * See the License for the specific language governing permissions and
  13  * limitations under the License.
  14  */
  15
  16 #ifndef included_clib_lock_h
  17 #define included_clib_lock_h
  18
  19 #include <vppinfra/clib.h>
  20 #include <vppinfra/atomics.h>
  21
  22 #if __x86_64__
  23 #define CLIB_PAUSE() __builtin_ia32_pause ()
  24 #elif defined (__aarch64__) || defined (__arm__)
  25 #define CLIB_PAUSE() __asm__ ("yield")
  26 #else
  27 #define CLIB_PAUSE()
  28 #endif
  29
  30 #if CLIB_DEBUG > 1
  31 #define CLIB_LOCK_DBG(_p)                               \
  32 do {                                                    \
  33     (*_p)->frame_address = __builtin_frame_address (0); \
  34     (*_p)->pid = getpid ();                             \
  35     (*_p)->thread_index = os_get_thread_index ();       \
  36 } while (0)
  37 #define CLIB_LOCK_DBG_CLEAR(_p)                         \
  38 do {                                                    \
  39     (*_p)->frame_address = 0;                           \
  40     (*_p)->pid = 0;                                     \
  41     (*_p)->thread_index = 0;                            \
  42 } while (0)
  43 #else
  44 #define CLIB_LOCK_DBG(_p)
  45 #define CLIB_LOCK_DBG_CLEAR(_p)
  46 #endif
  47
  48 #define CLIB_SPINLOCK_IS_LOCKED(_p) (*(_p))->lock
  49 #define CLIB_SPINLOCK_ASSERT_LOCKED(_p) ASSERT(CLIB_SPINLOCK_IS_LOCKED((_p)))
  50
  51 typedef struct
  52 {
  53   CLIB_CACHE_LINE_ALIGN_MARK (cacheline0);
  54   u32 lock;
  55 #if CLIB_DEBUG > 0
  56   pid_t pid;
  57   uword thread_index;
  58   void *frame_address;
  59 #endif
  60 } *clib_spinlock_t;
  61
  62 static inline void
  63 clib_spinlock_init (clib_spinlock_t * p)
  64 {
  65   *p = clib_mem_alloc_aligned (CLIB_CACHE_LINE_BYTES, CLIB_CACHE_LINE_BYTES);
  66   clib_memset ((void *) *p, 0, CLIB_CACHE_LINE_BYTES);
  67 }
  68
  69 static inline void
  70 clib_spinlock_free (clib_spinlock_t * p)
  71 {
  72   if (*p)
  73     {
  74       clib_mem_free ((void *) *p);
  75       *p = 0;
  76     }
  77 }
  78
  79 static_always_inline void
  80 clib_spinlock_lock (clib_spinlock_t * p)
  81 {
  82   u32 free = 0;
  83   while (!clib_atomic_cmp_and_swap_acq_relax_n (&(*p)->lock, &free, 1, 0))
  84     {
  85       /* atomic load limits number of compare_exchange executions */
  86       while (clib_atomic_load_relax_n (&(*p)->lock))
  87         CLIB_PAUSE ();
  88       /* on failure, compare_exchange writes (*p)->lock into free */
  89       free = 0;
  90     }
  91   CLIB_LOCK_DBG (p);
  92 }
  93
  94 static_always_inline int
  95 clib_spinlock_trylock (clib_spinlock_t * p)
  96 {
  97   if (PREDICT_FALSE (CLIB_SPINLOCK_IS_LOCKED (p)))
  98     return 0;
  99   clib_spinlock_lock (p);
 100   return 1;
 101 }
 102
 103 static_always_inline void
 104 clib_spinlock_lock_if_init (clib_spinlock_t * p)
 105 {
 106   if (PREDICT_FALSE (*p != 0))
 107     clib_spinlock_lock (p);
 108 }
 109
 110 static_always_inline int
 111 clib_spinlock_trylock_if_init (clib_spinlock_t * p)
 112 {
 113   if (PREDICT_FALSE (*p != 0))
 114     return clib_spinlock_trylock (p);
 115   return 1;
 116 }
 117
 118 static_always_inline void
 119 clib_spinlock_unlock (clib_spinlock_t * p)
 120 {
 121   CLIB_LOCK_DBG_CLEAR (p);
 122   /* Make sure all reads/writes are complete before releasing the lock */
 123   clib_atomic_release (&(*p)->lock);
 124 }
 125
 126 static_always_inline void
 127 clib_spinlock_unlock_if_init (clib_spinlock_t * p)
 128 {
 129   if (PREDICT_FALSE (*p != 0))
 130     clib_spinlock_unlock (p);
 131 }
 132
 133 /*
 134  * Readers-Writer Lock
 135  */
 136
 137 typedef struct clib_rw_lock_
 138 {
 139   CLIB_CACHE_LINE_ALIGN_MARK (cacheline0);
 140   /* -1 when W lock held, > 0 when R lock held */
 141   volatile i32 rw_cnt;
 142 #if CLIB_DEBUG > 0
 143   pid_t pid;
 144   uword thread_index;
 145   void *frame_address;
 146 #endif
 147 } *clib_rwlock_t;
 148
 149 always_inline void
 150 clib_rwlock_init (clib_rwlock_t * p)
 151 {
 152   *p = clib_mem_alloc_aligned (CLIB_CACHE_LINE_BYTES, CLIB_CACHE_LINE_BYTES);
 153   clib_memset ((void *) *p, 0, CLIB_CACHE_LINE_BYTES);
 154 }
 155
 156 always_inline void
 157 clib_rwlock_free (clib_rwlock_t * p)
 158 {
 159   if (*p)
 160     {
 161       clib_mem_free ((void *) *p);
 162       *p = 0;
 163     }
 164 }
 165
 166 always_inline void
 167 clib_rwlock_reader_lock (clib_rwlock_t * p)
 168 {
 169   i32 cnt;
 170   do
 171     {
 172       /* rwlock held by a writer */
 173       while ((cnt = clib_atomic_load_relax_n (&(*p)->rw_cnt)) < 0)
 174         CLIB_PAUSE ();
 175     }
 176   while (!clib_atomic_cmp_and_swap_acq_relax_n
 177          (&(*p)->rw_cnt, &cnt, cnt + 1, 1));
 178   CLIB_LOCK_DBG (p);
 179 }
 180
 181 always_inline void
 182 clib_rwlock_reader_unlock (clib_rwlock_t * p)
 183 {
 184   ASSERT ((*p)->rw_cnt > 0);
 185   CLIB_LOCK_DBG_CLEAR (p);
 186   clib_atomic_fetch_sub_rel (&(*p)->rw_cnt, 1);
 187 }
 188
 189 always_inline void
 190 clib_rwlock_writer_lock (clib_rwlock_t * p)
 191 {
 192   i32 cnt = 0;
 193   do
 194     {
 195       /* rwlock held by writer or reader(s) */
 196       while ((cnt = clib_atomic_load_relax_n (&(*p)->rw_cnt)) != 0)
 197         CLIB_PAUSE ();
 198     }
 199   while (!clib_atomic_cmp_and_swap_acq_relax_n (&(*p)->rw_cnt, &cnt, -1, 1));
 200   CLIB_LOCK_DBG (p);
 201 }
 202
 203 always_inline void
 204 clib_rwlock_writer_unlock (clib_rwlock_t * p)
 205 {
 206   CLIB_LOCK_DBG_CLEAR (p);
 207   clib_atomic_release (&(*p)->rw_cnt);
 208 }
 209
 210 #endif
 211
 212 /*
 213  * fd.io coding-style-patch-verification: ON
 214  *
 215  * Local Variables:
 216  * eval: (c-set-style "gnu")
 217  * End:
 218  */