lib/fat-rwlock.h

   1 /*
   2  * Copyright (c) 2013, 2014 Nicira, Inc.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at:
   7  *
   8  *     http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 #ifndef FAT_RWLOCK_H
  18 #define FAT_RWLOCK_H 1
  19
  20 #include "compiler.h"
  21 #include "openvswitch/list.h"
  22 #include "ovs-thread.h"
  23
  24 /* "Fat rwlock".
  25  *
  26  * This implements a reader-writer lock that uses a lot of memory (128 to 192
  27  * bytes per thread that takes the lock) but avoids cache line bouncing when
  28  * taking the read side.  Thus, a fat_rwlock is a good choice for rwlocks taken
  29  * frequently by readers.
  30  */
  31 struct OVS_LOCKABLE fat_rwlock {
  32     ovsthread_key_t key;
  33
  34     /* Contains "struct fat_rwlock_slot"s, one for each thread that has taken
  35      * this lock.  Guarded by 'mutex'. */
  36     struct ovs_list threads OVS_GUARDED;
  37     struct ovs_mutex mutex;
  38 };
  39
  40 void fat_rwlock_init(struct fat_rwlock *);
  41 void fat_rwlock_destroy(struct fat_rwlock *);
  42
  43 void fat_rwlock_rdlock(const struct fat_rwlock *rwlock) OVS_ACQ_RDLOCK(rwlock);
  44 int fat_rwlock_tryrdlock(const struct fat_rwlock *rwlock)
  45     OVS_TRY_RDLOCK(0, rwlock);
  46 void fat_rwlock_wrlock(const struct fat_rwlock *rwlock) OVS_ACQ_WRLOCK(rwlock);
  47 void fat_rwlock_unlock(const struct fat_rwlock *rwlock) OVS_RELEASES(rwlock);
  48
  49 #endif /* fat-rwlock.h */