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/cpumask.h>
  40 #include <linux/seqlock.h>
  41
  42 #ifdef CONFIG_RCU_CPU_STALL_DETECTOR
  43 #define RCU_SECONDS_TILL_STALL_CHECK    (10 * HZ) /* for rcp->jiffies_stall */
  44 #define RCU_SECONDS_TILL_STALL_RECHECK  (30 * HZ) /* for rcp->jiffies_stall */
  45 #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
  46
  47 /* Global control variables for rcupdate callback mechanism. */
  48 struct rcu_ctrlblk {
  49         long    cur;            /* Current batch number.                      */
  50         long    completed;      /* Number of the last completed batch         */
  51         long    pending;        /* Number of the last pending batch           */
  52 #ifdef CONFIG_RCU_CPU_STALL_DETECTOR
  53         unsigned long gp_start; /* Time at which GP started in jiffies. */
  54         unsigned long jiffies_stall;
  55                                 /* Time at which to check for CPU stalls. */
  56 #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
  57
  58         int     signaled;
  59
  60         spinlock_t      lock    ____cacheline_internodealigned_in_smp;
  61         DECLARE_BITMAP(cpumask, NR_CPUS); /* CPUs that need to switch for */
  62                                           /* current batch to proceed.     */
  63 } ____cacheline_internodealigned_in_smp;
  64
  65 /* Is batch a before batch b ? */
  66 static inline int rcu_batch_before(long a, long b)
  67 {
  68         return (a - b) < 0;
  69 }
  70
  71 /* Is batch a after batch b ? */
  72 static inline int rcu_batch_after(long a, long b)
  73 {
  74         return (a - b) > 0;
  75 }
  76
  77 /* Per-CPU data for Read-Copy UPdate. */
  78 struct rcu_data {
  79         /* 1) quiescent state handling : */
  80         long            quiescbatch;     /* Batch # for grace period */
  81         int             passed_quiesc;   /* User-mode/idle loop etc. */
  82         int             qs_pending;      /* core waits for quiesc state */
  83
  84         /* 2) batch handling */
  85         /*
  86          * if nxtlist is not NULL, then:
  87          * batch:
  88          *      The batch # for the last entry of nxtlist
  89          * [*nxttail[1], NULL = *nxttail[2]):
  90          *      Entries that batch # <= batch
  91          * [*nxttail[0], *nxttail[1]):
  92          *      Entries that batch # <= batch - 1
  93          * [nxtlist, *nxttail[0]):
  94          *      Entries that batch # <= batch - 2
  95          *      The grace period for these entries has completed, and
  96          *      the other grace-period-completed entries may be moved
  97          *      here temporarily in rcu_process_callbacks().
  98          */
  99         long            batch;
 100         struct rcu_head *nxtlist;
 101         struct rcu_head **nxttail[3];
 102         long            qlen;            /* # of queued callbacks */
 103         struct rcu_head *donelist;
 104         struct rcu_head **donetail;
 105         long            blimit;          /* Upper limit on a processed batch */
 106         int cpu;
 107         struct rcu_head barrier;
 108 };
 109
 110 /*
 111  * Increment the quiescent state counter.
 112  * The counter is a bit degenerated: We do not need to know
 113  * how many quiescent states passed, just if there was at least
 114  * one since the start of the grace period. Thus just a flag.
 115  */
 116 extern void rcu_qsctr_inc(int cpu);
 117 extern void rcu_bh_qsctr_inc(int cpu);
 118
 119 extern int rcu_pending(int cpu);
 120 extern int rcu_needs_cpu(int cpu);
 121
 122 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 123 extern struct lockdep_map rcu_lock_map;
 124 # define rcu_read_acquire()     \
 125                         lock_acquire(&rcu_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_)
 126 # define rcu_read_release()     lock_release(&rcu_lock_map, 1, _THIS_IP_)
 127 #else
 128 # define rcu_read_acquire()     do { } while (0)
 129 # define rcu_read_release()     do { } while (0)
 130 #endif
 131
 132 #define __rcu_read_lock() \
 133         do { \
 134                 preempt_disable(); \
 135                 __acquire(RCU); \
 136                 rcu_read_acquire(); \
 137         } while (0)
 138 #define __rcu_read_unlock() \
 139         do { \
 140                 rcu_read_release(); \
 141                 __release(RCU); \
 142                 preempt_enable(); \
 143         } while (0)
 144 #define __rcu_read_lock_bh() \
 145         do { \
 146                 local_bh_disable(); \
 147                 __acquire(RCU_BH); \
 148                 rcu_read_acquire(); \
 149         } while (0)
 150 #define __rcu_read_unlock_bh() \
 151         do { \
 152                 rcu_read_release(); \
 153                 __release(RCU_BH); \
 154                 local_bh_enable(); \
 155         } while (0)
 156
 157 #define __synchronize_sched() synchronize_rcu()
 158
 159 #define call_rcu_sched(head, func) call_rcu(head, func)
 160
 161 extern void __rcu_init(void);
 162 #define rcu_init_sched()        do { } while (0)
 163 extern void rcu_check_callbacks(int cpu, int user);
 164 extern void rcu_restart_cpu(int cpu);
 165
 166 extern long rcu_batches_completed(void);
 167 extern long rcu_batches_completed_bh(void);
 168
 169 #define rcu_enter_nohz()        do { } while (0)
 170 #define rcu_exit_nohz()         do { } while (0)
 171
 172 /* A context switch is a grace period for rcuclassic. */
 173 static inline int rcu_blocking_is_gp(void)
 174 {
 175         return num_online_cpus() == 1;
 176 }
 177
 178 #endif /* __LINUX_RCUCLASSIC_H */