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. */
  47 struct 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 ? */
  60 static inline int rcu_batch_before(long a, long b)
  61 {
  62         return (a - b) < 0;
  63 }
  64
  65 /* Is batch a after batch b ? */
  66 static 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  */
  76 struct 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
  96 DECLARE_PER_CPU(struct rcu_data, rcu_data);
  97 DECLARE_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  */
 105 static inline void rcu_qsctr_inc(int cpu)
 106 {
 107         struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
 108         rdp->passed_quiesc = 1;
 109 }
 110 static 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
 116 extern int rcu_pending(int cpu);
 117 extern int rcu_needs_cpu(int cpu);
 118
 119 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 120 extern 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
 156 extern void __rcu_init(void);
 157 extern void rcu_check_callbacks(int cpu, int user);
 158 extern void rcu_restart_cpu(int cpu);
 159
 160 extern long rcu_batches_completed(void);
 161 extern 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 */