include/linux/srcu.h

   1 /*
   2  * Sleepable Read-Copy Update mechanism for mutual exclusion
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  17  *
  18  * Copyright (C) IBM Corporation, 2006
  19  *
  20  * Author: Paul McKenney <paulmck@us.ibm.com>
  21  *
  22  * For detailed explanation of Read-Copy Update mechanism see -
  23  *              Documentation/RCU/ *.txt
  24  *
  25  */
  26
  27 #ifndef _LINUX_SRCU_H
  28 #define _LINUX_SRCU_H
  29
  30 #include <linux/wait.h>
  31
  32 struct srcu_struct_array {
  33         int c[2];
  34 };
  35
  36 struct srcu_struct {
  37         int completed;
  38         struct srcu_struct_array *per_cpu_ref;
  39         struct mutex mutex;
  40 };
  41
  42 #ifndef CONFIG_PREEMPT
  43 #define srcu_barrier() barrier()
  44 #else /* #ifndef CONFIG_PREEMPT */
  45 #define srcu_barrier()
  46 #endif /* #else #ifndef CONFIG_PREEMPT */
  47
  48 int init_srcu_struct(struct srcu_struct *sp);
  49 void cleanup_srcu_struct(struct srcu_struct *sp);
  50 int srcu_read_lock(struct srcu_struct *sp) __acquires(sp);
  51 void srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp);
  52 void synchronize_srcu(struct srcu_struct *sp);
  53 long srcu_batches_completed(struct srcu_struct *sp);
  54
  55 /*
  56  * fully compatible with srcu, but optimized for writers.
  57  */
  58
  59 struct qrcu_struct {
  60         int completed;
  61         atomic_t ctr[2];
  62         wait_queue_head_t wq;
  63         struct mutex mutex;
  64 };
  65
  66 int init_qrcu_struct(struct qrcu_struct *qp);
  67 int qrcu_read_lock(struct qrcu_struct *qp);
  68 void qrcu_read_unlock(struct qrcu_struct *qp, int idx);
  69 void synchronize_qrcu(struct qrcu_struct *qp);
  70
  71 static inline void cleanup_qrcu_struct(struct qrcu_struct *qp)
  72 {
  73 }
  74
  75 #endif