Subversion Repositories shark

Rev

Go to most recent revision | Details | Last modification | View Log | RSS feed

Rev Author Line No. Line
422 giacomo 1
/*
2
 * Read-Copy Update mechanism for mutual exclusion
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, 2001
19
 *
20
 * Author: Dipankar Sarma <dipankar@in.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
 *              http://lse.sourceforge.net/locking/rcupdate.html
30
 *
31
 */
32
 
33
#ifndef __LINUX_RCUPDATE_H
34
#define __LINUX_RCUPDATE_H
35
 
36
#ifdef __KERNEL__
37
 
38
#include <linux/cache.h>
39
#include <linux/list.h>
40
#include <linux/spinlock.h>
41
#include <linux/threads.h>
42
#include <linux/percpu.h>
43
#include <linux/cpumask.h>
44
 
45
/**
46
 * struct rcu_head - callback structure for use with RCU
47
 * @list: list_head to queue the update requests
48
 * @func: actual update function to call after the grace period.
49
 * @arg: argument to be passed to the actual update function.
50
 */
51
struct rcu_head {
52
        struct list_head list;
53
        void (*func)(void *obj);
54
        void *arg;
55
};
56
 
57
#define RCU_HEAD_INIT(head) \
58
                { list: LIST_HEAD_INIT(head.list), func: NULL, arg: NULL }
59
#define RCU_HEAD(head) struct rcu_head head = RCU_HEAD_INIT(head)
60
#define INIT_RCU_HEAD(ptr) do { \
61
       INIT_LIST_HEAD(&(ptr)->list); (ptr)->func = NULL; (ptr)->arg = NULL; \
62
} while (0)
63
 
64
 
65
 
66
/* Control variables for rcupdate callback mechanism. */
67
struct rcu_ctrlblk {
68
        spinlock_t      mutex;          /* Guard this struct                  */
69
        long            curbatch;       /* Current batch number.              */
70
        long            maxbatch;       /* Max requested batch number.        */
71
        cpumask_t       rcu_cpu_mask;   /* CPUs that need to switch in order  */
72
                                        /* for current batch to proceed.      */
73
};
74
 
75
/* Is batch a before batch b ? */
76
static inline int rcu_batch_before(long a, long b)
77
{
78
        return (a - b) < 0;
79
}
80
 
81
/* Is batch a after batch b ? */
82
static inline int rcu_batch_after(long a, long b)
83
{
84
        return (a - b) > 0;
85
}
86
 
87
/*
88
 * Per-CPU data for Read-Copy UPdate.
89
 * nxtlist - new callbacks are added here
90
 * curlist - current batch for which quiescent cycle started if any
91
 */
92
struct rcu_data {
93
        long            qsctr;           /* User-mode/idle loop etc. */
94
        long            last_qsctr;      /* value of qsctr at beginning */
95
                                         /* of rcu grace period */
96
        long            batch;           /* Batch # for current RCU batch */
97
        struct list_head  nxtlist;
98
        struct list_head  curlist;
99
};
100
 
101
DECLARE_PER_CPU(struct rcu_data, rcu_data);
102
extern struct rcu_ctrlblk rcu_ctrlblk;
103
 
104
#define RCU_qsctr(cpu)          (per_cpu(rcu_data, (cpu)).qsctr)
105
#define RCU_last_qsctr(cpu)     (per_cpu(rcu_data, (cpu)).last_qsctr)
106
#define RCU_batch(cpu)          (per_cpu(rcu_data, (cpu)).batch)
107
#define RCU_nxtlist(cpu)        (per_cpu(rcu_data, (cpu)).nxtlist)
108
#define RCU_curlist(cpu)        (per_cpu(rcu_data, (cpu)).curlist)
109
 
110
#define RCU_QSCTR_INVALID       0
111
 
112
static inline int rcu_pending(int cpu)
113
{
114
        if ((!list_empty(&RCU_curlist(cpu)) &&
115
             rcu_batch_before(RCU_batch(cpu), rcu_ctrlblk.curbatch)) ||
116
            (list_empty(&RCU_curlist(cpu)) &&
117
                         !list_empty(&RCU_nxtlist(cpu))) ||
118
            cpu_isset(cpu, rcu_ctrlblk.rcu_cpu_mask))
119
                return 1;
120
        else
121
                return 0;
122
}
123
 
124
#define rcu_read_lock()         preempt_disable()
125
#define rcu_read_unlock()       preempt_enable()
126
 
127
extern void rcu_init(void);
128
extern void rcu_check_callbacks(int cpu, int user);
129
 
130
/* Exported interfaces */
131
extern void FASTCALL(call_rcu(struct rcu_head *head,
132
                          void (*func)(void *arg), void *arg));
133
extern void synchronize_kernel(void);
134
 
135
#endif /* __KERNEL__ */
136
#endif /* __LINUX_RCUPDATE_H */