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1da177e4 LT |
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 | * | |
01c1c660 | 18 | * Copyright IBM Corporation, 2001 |
1da177e4 LT |
19 | * |
20 | * Authors: Dipankar Sarma <dipankar@in.ibm.com> | |
21 | * Manfred Spraul <manfred@colorfullife.com> | |
a71fca58 | 22 | * |
1da177e4 LT |
23 | * Based on the original work by Paul McKenney <paulmck@us.ibm.com> |
24 | * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. | |
25 | * Papers: | |
26 | * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf | |
27 | * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001) | |
28 | * | |
29 | * For detailed explanation of Read-Copy Update mechanism see - | |
a71fca58 | 30 | * http://lse.sourceforge.net/locking/rcupdate.html |
1da177e4 LT |
31 | * |
32 | */ | |
33 | #include <linux/types.h> | |
34 | #include <linux/kernel.h> | |
35 | #include <linux/init.h> | |
36 | #include <linux/spinlock.h> | |
37 | #include <linux/smp.h> | |
38 | #include <linux/interrupt.h> | |
39 | #include <linux/sched.h> | |
40 | #include <asm/atomic.h> | |
41 | #include <linux/bitops.h> | |
1da177e4 LT |
42 | #include <linux/percpu.h> |
43 | #include <linux/notifier.h> | |
1da177e4 | 44 | #include <linux/cpu.h> |
9331b315 | 45 | #include <linux/mutex.h> |
01c1c660 | 46 | #include <linux/module.h> |
d9f1bb6a | 47 | #include <linux/kernel_stat.h> |
e3818b8d | 48 | #include <linux/hardirq.h> |
1da177e4 | 49 | |
162cc279 PM |
50 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
51 | static struct lock_class_key rcu_lock_key; | |
52 | struct lockdep_map rcu_lock_map = | |
53 | STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key); | |
54 | EXPORT_SYMBOL_GPL(rcu_lock_map); | |
632ee200 PM |
55 | |
56 | static struct lock_class_key rcu_bh_lock_key; | |
57 | struct lockdep_map rcu_bh_lock_map = | |
58 | STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_bh", &rcu_bh_lock_key); | |
59 | EXPORT_SYMBOL_GPL(rcu_bh_lock_map); | |
60 | ||
61 | static struct lock_class_key rcu_sched_lock_key; | |
62 | struct lockdep_map rcu_sched_lock_map = | |
63 | STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_sched", &rcu_sched_lock_key); | |
64 | EXPORT_SYMBOL_GPL(rcu_sched_lock_map); | |
162cc279 PM |
65 | #endif |
66 | ||
d9f1bb6a | 67 | int rcu_scheduler_active __read_mostly; |
f5f65409 | 68 | EXPORT_SYMBOL_GPL(rcu_scheduler_active); |
d9f1bb6a | 69 | |
e3818b8d PM |
70 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
71 | ||
bc293d62 PM |
72 | int debug_lockdep_rcu_enabled(void) |
73 | { | |
74 | return rcu_scheduler_active && debug_locks && | |
75 | current->lockdep_recursion == 0; | |
76 | } | |
77 | EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled); | |
78 | ||
e3818b8d PM |
79 | /** |
80 | * rcu_read_lock_bh_held - might we be in RCU-bh read-side critical section? | |
81 | * | |
82 | * Check for bottom half being disabled, which covers both the | |
83 | * CONFIG_PROVE_RCU and not cases. Note that if someone uses | |
84 | * rcu_read_lock_bh(), but then later enables BH, lockdep (if enabled) | |
85 | * will show the situation. | |
86 | * | |
87 | * Check debug_lockdep_rcu_enabled() to prevent false positives during boot. | |
88 | */ | |
89 | int rcu_read_lock_bh_held(void) | |
90 | { | |
91 | if (!debug_lockdep_rcu_enabled()) | |
92 | return 1; | |
93 | return in_softirq(); | |
94 | } | |
95 | EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held); | |
96 | ||
97 | #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ | |
98 | ||
d9f1bb6a PM |
99 | /* |
100 | * This function is invoked towards the end of the scheduler's initialization | |
101 | * process. Before this is called, the idle task might contain | |
102 | * RCU read-side critical sections (during which time, this idle | |
103 | * task is booting the system). After this function is called, the | |
104 | * idle tasks are prohibited from containing RCU read-side critical | |
105 | * sections. | |
106 | */ | |
107 | void rcu_scheduler_starting(void) | |
108 | { | |
109 | WARN_ON(num_online_cpus() != 1); | |
110 | WARN_ON(nr_context_switches() > 0); | |
111 | rcu_scheduler_active = 1; | |
112 | } | |
113 | ||
fbf6bfca PM |
114 | /* |
115 | * Awaken the corresponding synchronize_rcu() instance now that a | |
116 | * grace period has elapsed. | |
117 | */ | |
4446a36f | 118 | void wakeme_after_rcu(struct rcu_head *head) |
21a1ea9e | 119 | { |
01c1c660 PM |
120 | struct rcu_synchronize *rcu; |
121 | ||
122 | rcu = container_of(head, struct rcu_synchronize, head); | |
123 | complete(&rcu->completion); | |
21a1ea9e | 124 | } |