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