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