LXR linux/include/linux/rcuclassic.h

   1/*
   2 * Read-Copy Update mechanism for mutual exclusion (classic version)
   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 IBM Corporation, 2001
  19 *
  20 * Author: Dipankar Sarma <dipankar@in.ibm.com>
  21 *
  22 * Based on the original work by Paul McKenney <paulmck@us.ibm.com>
  23 * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
  24 * Papers:
  25 * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf
  26 * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001)
  27 *
  28 * For detailed explanation of Read-Copy Update mechanism see -
  29 *              Documentation/RCU
  30 *
  31 */
  32
  33#ifndef __LINUX_RCUCLASSIC_H
  34#define __LINUX_RCUCLASSIC_H
  35
  36#ifdef __KERNEL__
  37
  38#include <linux/cache.h>
  39#include <linux/spinlock.h>
  40#include <linux/threads.h>
  41#include <linux/percpu.h>
  42#include <linux/cpumask.h>
  43#include <linux/seqlock.h>
  44
  45
  46/* Global control variables for rcupdate callback mechanism. */
  47struct rcu_ctrlblk {
  48        long    cur;            /* Current batch number.                      */
  49        long    completed;      /* Number of the last completed batch         */
  50        int     next_pending;   /* Is the next batch already waiting?         */
  51
  52        int     signaled;
  53
  54        spinlock_t      lock    ____cacheline_internodealigned_in_smp;
  55        cpumask_t       cpumask; /* CPUs that need to switch in order    */
  56                                 /* for current batch to proceed.        */
  57} ____cacheline_internodealigned_in_smp;
  58
  59/* Is batch a before batch b ? */
  60static inline int rcu_batch_before(long a, long b)
  61{
  62        return (a - b) < 0;
  63}
  64
  65/* Is batch a after batch b ? */
  66static inline int rcu_batch_after(long a, long b)
  67{
  68        return (a - b) > 0;
  69}
  70
  71/*
  72 * Per-CPU data for Read-Copy UPdate.
  73 * nxtlist - new callbacks are added here
  74 * curlist - current batch for which quiescent cycle started if any
  75 */
  76struct rcu_data {
  77        /* 1) quiescent state handling : */
  78        long            quiescbatch;     /* Batch # for grace period */
  79        int             passed_quiesc;   /* User-mode/idle loop etc. */
  80        int             qs_pending;      /* core waits for quiesc state */
  81
  82        /* 2) batch handling */
  83        long            batch;           /* Batch # for current RCU batch */
  84        struct rcu_head *nxtlist;
  85        struct rcu_head **nxttail;
  86        long            qlen;            /* # of queued callbacks */
  87        struct rcu_head *curlist;
  88        struct rcu_head **curtail;
  89        struct rcu_head *donelist;
  90        struct rcu_head **donetail;
  91        long            blimit;          /* Upper limit on a processed batch */
  92        int cpu;
  93        struct rcu_head barrier;
  94};
  95
  96DECLARE_PER_CPU(struct rcu_data, rcu_data);
  97DECLARE_PER_CPU(struct rcu_data, rcu_bh_data);
  98
  99/*
 100 * Increment the quiescent state counter.
 101 * The counter is a bit degenerated: We do not need to know
 102 * how many quiescent states passed, just if there was at least
 103 * one since the start of the grace period. Thus just a flag.
 104 */
 105static inline void rcu_qsctr_inc(int cpu)
 106{
 107        struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
 108        rdp->passed_quiesc = 1;
 109}
 110static inline void rcu_bh_qsctr_inc(int cpu)
 111{
 112        struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu);
 113        rdp->passed_quiesc = 1;
 114}
 115
 116extern int rcu_pending(int cpu);
 117extern int rcu_needs_cpu(int cpu);
 118
 119#ifdef CONFIG_DEBUG_LOCK_ALLOC
 120extern struct lockdep_map rcu_lock_map;
 121# define rcu_read_acquire()     \
 122                        lock_acquire(&rcu_lock_map, 0, 0, 2, 1, _THIS_IP_)
 123# define rcu_read_release()     lock_release(&rcu_lock_map, 1, _THIS_IP_)
 124#else
 125# define rcu_read_acquire()     do { } while (0)
 126# define rcu_read_release()     do { } while (0)
 127#endif
 128
 129#define __rcu_read_lock() \
 130        do { \
 131                preempt_disable(); \
 132                __acquire(RCU); \
 133                rcu_read_acquire(); \
 134        } while (0)
 135#define __rcu_read_unlock() \
 136        do { \
 137                rcu_read_release(); \
 138                __release(RCU); \
 139                preempt_enable(); \
 140        } while (0)
 141#define __rcu_read_lock_bh() \
 142        do { \
 143                local_bh_disable(); \
 144                __acquire(RCU_BH); \
 145                rcu_read_acquire(); \
 146        } while (0)
 147#define __rcu_read_unlock_bh() \
 148        do { \
 149                rcu_read_release(); \
 150                __release(RCU_BH); \
 151                local_bh_enable(); \
 152        } while (0)
 153
 154#define __synchronize_sched() synchronize_rcu()
 155
 156extern void __rcu_init(void);
 157extern void rcu_check_callbacks(int cpu, int user);
 158extern void rcu_restart_cpu(int cpu);
 159
 160extern long rcu_batches_completed(void);
 161extern long rcu_batches_completed_bh(void);
 162
 163#define rcu_enter_nohz()        do { } while (0)
 164#define rcu_exit_nohz()         do { } while (0)
 165
 166#endif /* __KERNEL__ */
 167#endif /* __LINUX_RCUCLASSIC_H */
 168