linux/include/linux/rcupreempt.h
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   1/*
   2 * Read-Copy Update mechanism for mutual exclusion (RT implementation)
   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 (C) IBM Corporation, 2006
  19 *
  20 * Author:  Paul McKenney <paulmck@us.ibm.com>
  21 *
  22 * Based on the original work by Paul McKenney <paul.mckenney@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_RCUPREEMPT_H
  34#define __LINUX_RCUPREEMPT_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
  43struct rcu_dyntick_sched {
  44        int dynticks;
  45        int dynticks_snap;
  46        int sched_qs;
  47        int sched_qs_snap;
  48        int sched_dynticks_snap;
  49};
  50
  51DECLARE_PER_CPU(struct rcu_dyntick_sched, rcu_dyntick_sched);
  52
  53static inline void rcu_qsctr_inc(int cpu)
  54{
  55        struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu);
  56
  57        rdssp->sched_qs++;
  58}
  59#define rcu_bh_qsctr_inc(cpu)
  60
  61/*
  62 * Someone might want to pass call_rcu_bh as a function pointer.
  63 * So this needs to just be a rename and not a macro function.
  64 *  (no parentheses)
  65 */
  66#define call_rcu_bh             call_rcu
  67
  68/**
  69 * call_rcu_sched - Queue RCU callback for invocation after sched grace period.
  70 * @head: structure to be used for queueing the RCU updates.
  71 * @func: actual update function to be invoked after the grace period
  72 *
  73 * The update function will be invoked some time after a full
  74 * synchronize_sched()-style grace period elapses, in other words after
  75 * all currently executing preempt-disabled sections of code (including
  76 * hardirq handlers, NMI handlers, and local_irq_save() blocks) have
  77 * completed.
  78 */
  79extern void call_rcu_sched(struct rcu_head *head,
  80                           void (*func)(struct rcu_head *head));
  81
  82extern void __rcu_read_lock(void)       __acquires(RCU);
  83extern void __rcu_read_unlock(void)     __releases(RCU);
  84extern int rcu_pending(int cpu);
  85extern int rcu_needs_cpu(int cpu);
  86
  87#define __rcu_read_lock_bh()    { rcu_read_lock(); local_bh_disable(); }
  88#define __rcu_read_unlock_bh()  { local_bh_enable(); rcu_read_unlock(); }
  89
  90extern void __synchronize_sched(void);
  91
  92extern void __rcu_init(void);
  93extern void rcu_init_sched(void);
  94extern void rcu_check_callbacks(int cpu, int user);
  95extern void rcu_restart_cpu(int cpu);
  96extern long rcu_batches_completed(void);
  97
  98/*
  99 * Return the number of RCU batches processed thus far. Useful for debug
 100 * and statistic. The _bh variant is identifcal to straight RCU
 101 */
 102static inline long rcu_batches_completed_bh(void)
 103{
 104        return rcu_batches_completed();
 105}
 106
 107#ifdef CONFIG_RCU_TRACE
 108struct rcupreempt_trace;
 109extern long *rcupreempt_flipctr(int cpu);
 110extern long rcupreempt_data_completed(void);
 111extern int rcupreempt_flip_flag(int cpu);
 112extern int rcupreempt_mb_flag(int cpu);
 113extern char *rcupreempt_try_flip_state_name(void);
 114extern struct rcupreempt_trace *rcupreempt_trace_cpu(int cpu);
 115#endif
 116
 117struct softirq_action;
 118
 119#ifdef CONFIG_NO_HZ
 120
 121static inline void rcu_enter_nohz(void)
 122{
 123        static DEFINE_RATELIMIT_STATE(rs, 10 * HZ, 1);
 124
 125        smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */
 126        __get_cpu_var(rcu_dyntick_sched).dynticks++;
 127        WARN_ON_RATELIMIT(__get_cpu_var(rcu_dyntick_sched).dynticks & 0x1, &rs);
 128}
 129
 130static inline void rcu_exit_nohz(void)
 131{
 132        static DEFINE_RATELIMIT_STATE(rs, 10 * HZ, 1);
 133
 134        __get_cpu_var(rcu_dyntick_sched).dynticks++;
 135        smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */
 136        WARN_ON_RATELIMIT(!(__get_cpu_var(rcu_dyntick_sched).dynticks & 0x1),
 137                                &rs);
 138}
 139
 140#else /* CONFIG_NO_HZ */
 141#define rcu_enter_nohz()        do { } while (0)
 142#define rcu_exit_nohz()         do { } while (0)
 143#endif /* CONFIG_NO_HZ */
 144
 145#endif /* __LINUX_RCUPREEMPT_H */
 146
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