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 #ifdef CONFIG_RCU_CPU_STALL_DETECTOR
  44 #define RCU_SECONDS_TILL_STALL_CHECK    (10 * HZ) /* for rcp->jiffies_stall */
  45 #define RCU_SECONDS_TILL_STALL_RECHECK  (30 * HZ) /* for rcp->jiffies_stall */
  46 #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
  47
  48 /* Global control variables for rcupdate callback mechanism. */
  49 struct rcu_ctrlblk {
  50         long    cur;            /* Current batch number.                      */
  51         long    completed;      /* Number of the last completed batch         */
  52         long    pending;        /* Number of the last pending batch           */
  53 #ifdef CONFIG_RCU_CPU_STALL_DETECTOR
  54         unsigned long gp_start; /* Time at which GP started in jiffies. */
  55         unsigned long jiffies_stall;
  56                                 /* Time at which to check for CPU stalls. */
  57 #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
  58
  59         int     signaled;
  60
  61         spinlock_t      lock    ____cacheline_internodealigned_in_smp;
  62         DECLARE_BITMAP(cpumask, NR_CPUS); /* CPUs that need to switch for */
  63                                           /* current batch to proceed.     */
  64 } ____cacheline_internodealigned_in_smp;
  65
  66 /* Is batch a before batch b ? */
  67 static inline int rcu_batch_before(long a, long b)
  68 {
  69         return (a - b) < 0;
  70 }
  71
  72 /* Is batch a after batch b ? */
  73 static inline int rcu_batch_after(long a, long b)
  74 {
  75         return (a - b) > 0;
  76 }
  77
  78 /* Per-CPU data for Read-Copy UPdate. */
  79 struct rcu_data {
  80         /* 1) quiescent state handling : */
  81         long            quiescbatch;     /* Batch # for grace period */
  82         int             passed_quiesc;   /* User-mode/idle loop etc. */
  83         int             qs_pending;      /* core waits for quiesc state */
  84
  85         /* 2) batch handling */
  86         /*
  87          * if nxtlist is not NULL, then:
  88          * batch:
  89          *      The batch # for the last entry of nxtlist
  90          * [*nxttail[1], NULL = *nxttail[2]):
  91          *      Entries that batch # <= batch
  92          * [*nxttail[0], *nxttail[1]):
  93          *      Entries that batch # <= batch - 1
  94          * [nxtlist, *nxttail[0]):
  95          *      Entries that batch # <= batch - 2
  96          *      The grace period for these entries has completed, and
  97          *      the other grace-period-completed entries may be moved
  98          *      here temporarily in rcu_process_callbacks().
  99          */
 100         long            batch;
 101         struct rcu_head *nxtlist;
 102         struct rcu_head **nxttail[3];
 103         long            qlen;            /* # of queued callbacks */
 104         struct rcu_head *donelist;
 105         struct rcu_head **donetail;
 106         long            blimit;          /* Upper limit on a processed batch */
 107         int cpu;
 108         struct rcu_head barrier;
 109 };
 110
 111 DECLARE_PER_CPU(struct rcu_data, rcu_data);
 112 DECLARE_PER_CPU(struct rcu_data, rcu_bh_data);
 113
 114 /*
 115  * Increment the quiescent state counter.
 116  * The counter is a bit degenerated: We do not need to know
 117  * how many quiescent states passed, just if there was at least
 118  * one since the start of the grace period. Thus just a flag.
 119  */
 120 static inline void rcu_qsctr_inc(int cpu)
 121 {
 122         struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
 123         rdp->passed_quiesc = 1;
 124 }
 125 static inline void rcu_bh_qsctr_inc(int cpu)
 126 {
 127         struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu);
 128         rdp->passed_quiesc = 1;
 129 }
 130
 131 extern int rcu_pending(int cpu);
 132 extern int rcu_needs_cpu(int cpu);
 133
 134 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 135 extern struct lockdep_map rcu_lock_map;
 136 # define rcu_read_acquire()     \
 137                         lock_acquire(&rcu_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_)
 138 # define rcu_read_release()     lock_release(&rcu_lock_map, 1, _THIS_IP_)
 139 #else
 140 # define rcu_read_acquire()     do { } while (0)
 141 # define rcu_read_release()     do { } while (0)
 142 #endif
 143
 144 #define __rcu_read_lock() \
 145         do { \
 146                 preempt_disable(); \
 147                 __acquire(RCU); \
 148                 rcu_read_acquire(); \
 149         } while (0)
 150 #define __rcu_read_unlock() \
 151         do { \
 152                 rcu_read_release(); \
 153                 __release(RCU); \
 154                 preempt_enable(); \
 155         } while (0)
 156 #define __rcu_read_lock_bh() \
 157         do { \
 158                 local_bh_disable(); \
 159                 __acquire(RCU_BH); \
 160                 rcu_read_acquire(); \
 161         } while (0)
 162 #define __rcu_read_unlock_bh() \
 163         do { \
 164                 rcu_read_release(); \
 165                 __release(RCU_BH); \
 166                 local_bh_enable(); \
 167         } while (0)
 168
 169 #define __synchronize_sched() synchronize_rcu()
 170
 171 #define call_rcu_sched(head, func) call_rcu(head, func)
 172
 173 extern void __rcu_init(void);
 174 #define rcu_init_sched()        do { } while (0)
 175 extern void rcu_check_callbacks(int cpu, int user);
 176 extern void rcu_restart_cpu(int cpu);
 177
 178 extern long rcu_batches_completed(void);
 179 extern long rcu_batches_completed_bh(void);
 180
 181 #define rcu_enter_nohz()        do { } while (0)
 182 #define rcu_exit_nohz()         do { } while (0)
 183
 184 /* A context switch is a grace period for rcuclassic. */
 185 static inline int rcu_blocking_is_gp(void)
 186 {
 187         return num_online_cpus() == 1;
 188 }
 189
 190 #endif /* __LINUX_RCUCLASSIC_H */