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Linux kernel mirror (for testing)
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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#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
44/* Global control variables for rcupdate callback mechanism. */
45struct rcu_ctrlblk {
46 long cur; /* Current batch number. */
47 long completed; /* Number of the last completed batch */
48 int next_pending; /* Is the next batch already waiting? */
49
50 int signaled;
51
52 spinlock_t lock ____cacheline_internodealigned_in_smp;
53 cpumask_t cpumask; /* CPUs that need to switch in order */
54 /* for current batch to proceed. */
55} ____cacheline_internodealigned_in_smp;
56
57/* Is batch a before batch b ? */
58static inline int rcu_batch_before(long a, long b)
59{
60 return (a - b) < 0;
61}
62
63/* Is batch a after batch b ? */
64static inline int rcu_batch_after(long a, long b)
65{
66 return (a - b) > 0;
67}
68
69/*
70 * Per-CPU data for Read-Copy UPdate.
71 * nxtlist - new callbacks are added here
72 * curlist - current batch for which quiescent cycle started if any
73 */
74struct rcu_data {
75 /* 1) quiescent state handling : */
76 long quiescbatch; /* Batch # for grace period */
77 int passed_quiesc; /* User-mode/idle loop etc. */
78 int qs_pending; /* core waits for quiesc state */
79
80 /* 2) batch handling */
81 long batch; /* Batch # for current RCU batch */
82 struct rcu_head *nxtlist;
83 struct rcu_head **nxttail;
84 long qlen; /* # of queued callbacks */
85 struct rcu_head *curlist;
86 struct rcu_head **curtail;
87 struct rcu_head *donelist;
88 struct rcu_head **donetail;
89 long blimit; /* Upper limit on a processed batch */
90 int cpu;
91 struct rcu_head barrier;
92};
93
94DECLARE_PER_CPU(struct rcu_data, rcu_data);
95DECLARE_PER_CPU(struct rcu_data, rcu_bh_data);
96
97/*
98 * Increment the quiescent state counter.
99 * The counter is a bit degenerated: We do not need to know
100 * how many quiescent states passed, just if there was at least
101 * one since the start of the grace period. Thus just a flag.
102 */
103static inline void rcu_qsctr_inc(int cpu)
104{
105 struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
106 rdp->passed_quiesc = 1;
107}
108static inline void rcu_bh_qsctr_inc(int cpu)
109{
110 struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu);
111 rdp->passed_quiesc = 1;
112}
113
114extern int rcu_pending(int cpu);
115extern int rcu_needs_cpu(int cpu);
116
117#ifdef CONFIG_DEBUG_LOCK_ALLOC
118extern struct lockdep_map rcu_lock_map;
119# define rcu_read_acquire() \
120 lock_acquire(&rcu_lock_map, 0, 0, 2, 1, _THIS_IP_)
121# define rcu_read_release() lock_release(&rcu_lock_map, 1, _THIS_IP_)
122#else
123# define rcu_read_acquire() do { } while (0)
124# define rcu_read_release() do { } while (0)
125#endif
126
127#define __rcu_read_lock() \
128 do { \
129 preempt_disable(); \
130 __acquire(RCU); \
131 rcu_read_acquire(); \
132 } while (0)
133#define __rcu_read_unlock() \
134 do { \
135 rcu_read_release(); \
136 __release(RCU); \
137 preempt_enable(); \
138 } while (0)
139#define __rcu_read_lock_bh() \
140 do { \
141 local_bh_disable(); \
142 __acquire(RCU_BH); \
143 rcu_read_acquire(); \
144 } while (0)
145#define __rcu_read_unlock_bh() \
146 do { \
147 rcu_read_release(); \
148 __release(RCU_BH); \
149 local_bh_enable(); \
150 } while (0)
151
152#define __synchronize_sched() synchronize_rcu()
153
154extern void __rcu_init(void);
155extern void rcu_check_callbacks(int cpu, int user);
156extern void rcu_restart_cpu(int cpu);
157
158extern long rcu_batches_completed(void);
159extern long rcu_batches_completed_bh(void);
160
161#define rcu_enter_nohz() do { } while (0)
162#define rcu_exit_nohz() do { } while (0)
163
164#endif /* __LINUX_RCUCLASSIC_H */