2 * Read-Copy Update mechanism for mutual exclusion (classic version)
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.
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.
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.
18 * Copyright IBM Corporation, 2001
20 * Author: Dipankar Sarma <dipankar@in.ibm.com>
22 * Based on the original work by Paul McKenney <paulmck@us.ibm.com>
23 * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
25 * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf
26 * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001)
28 * For detailed explanation of Read-Copy Update mechanism see -
33 #ifndef __LINUX_RCUCLASSIC_H
34 #define __LINUX_RCUCLASSIC_H
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>
44 /* Global control variables for rcupdate callback mechanism. */
46 long cur
; /* Current batch number. */
47 long completed
; /* Number of the last completed batch */
48 long pending
; /* Number of the last pending batch */
49 #ifdef CONFIG_DEBUG_RCU_STALL
50 unsigned long gp_check
; /* Time grace period should end, in seconds. */
51 #endif /* #ifdef CONFIG_DEBUG_RCU_STALL */
55 spinlock_t lock ____cacheline_internodealigned_in_smp
;
56 cpumask_t cpumask
; /* CPUs that need to switch in order */
57 /* for current batch to proceed. */
58 } ____cacheline_internodealigned_in_smp
;
60 /* Is batch a before batch b ? */
61 static inline int rcu_batch_before(long a
, long b
)
66 /* Is batch a after batch b ? */
67 static inline int rcu_batch_after(long a
, long b
)
72 /* Per-CPU data for Read-Copy UPdate. */
74 /* 1) quiescent state handling : */
75 long quiescbatch
; /* Batch # for grace period */
76 int passed_quiesc
; /* User-mode/idle loop etc. */
77 int qs_pending
; /* core waits for quiesc state */
79 /* 2) batch handling */
81 * if nxtlist is not NULL, then:
83 * The batch # for the last entry of nxtlist
84 * [*nxttail[1], NULL = *nxttail[2]):
85 * Entries that batch # <= batch
86 * [*nxttail[0], *nxttail[1]):
87 * Entries that batch # <= batch - 1
88 * [nxtlist, *nxttail[0]):
89 * Entries that batch # <= batch - 2
90 * The grace period for these entries has completed, and
91 * the other grace-period-completed entries may be moved
92 * here temporarily in rcu_process_callbacks().
95 struct rcu_head
*nxtlist
;
96 struct rcu_head
**nxttail
[3];
97 long qlen
; /* # of queued callbacks */
98 struct rcu_head
*donelist
;
99 struct rcu_head
**donetail
;
100 long blimit
; /* Upper limit on a processed batch */
102 struct rcu_head barrier
;
105 DECLARE_PER_CPU(struct rcu_data
, rcu_data
);
106 DECLARE_PER_CPU(struct rcu_data
, rcu_bh_data
);
109 * Increment the quiescent state counter.
110 * The counter is a bit degenerated: We do not need to know
111 * how many quiescent states passed, just if there was at least
112 * one since the start of the grace period. Thus just a flag.
114 static inline void rcu_qsctr_inc(int cpu
)
116 struct rcu_data
*rdp
= &per_cpu(rcu_data
, cpu
);
117 rdp
->passed_quiesc
= 1;
119 static inline void rcu_bh_qsctr_inc(int cpu
)
121 struct rcu_data
*rdp
= &per_cpu(rcu_bh_data
, cpu
);
122 rdp
->passed_quiesc
= 1;
125 extern int rcu_pending(int cpu
);
126 extern int rcu_needs_cpu(int cpu
);
128 #ifdef CONFIG_DEBUG_LOCK_ALLOC
129 extern struct lockdep_map rcu_lock_map
;
130 # define rcu_read_acquire() \
131 lock_acquire(&rcu_lock_map, 0, 0, 2, 1, _THIS_IP_)
132 # define rcu_read_release() lock_release(&rcu_lock_map, 1, _THIS_IP_)
134 # define rcu_read_acquire() do { } while (0)
135 # define rcu_read_release() do { } while (0)
138 #define __rcu_read_lock() \
142 rcu_read_acquire(); \
144 #define __rcu_read_unlock() \
146 rcu_read_release(); \
150 #define __rcu_read_lock_bh() \
152 local_bh_disable(); \
154 rcu_read_acquire(); \
156 #define __rcu_read_unlock_bh() \
158 rcu_read_release(); \
163 #define __synchronize_sched() synchronize_rcu()
165 #define call_rcu_sched(head, func) call_rcu(head, func)
167 extern void __rcu_init(void);
168 #define rcu_init_sched() do { } while (0)
169 extern void rcu_check_callbacks(int cpu
, int user
);
170 extern void rcu_restart_cpu(int cpu
);
172 extern long rcu_batches_completed(void);
173 extern long rcu_batches_completed_bh(void);
175 #define rcu_enter_nohz() do { } while (0)
176 #define rcu_exit_nohz() do { } while (0)
178 #endif /* __LINUX_RCUCLASSIC_H */