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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 */