1 /*
2 * Read-Copy Update definitions shared among RCU implementations.
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, you can access it online at
16 * http://www.gnu.org/licenses/gpl-2.0.html.
17 *
18 * Copyright IBM Corporation, 2011
19 *
20 * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
21 */
22
23 #ifndef __LINUX_RCU_H
24 #define __LINUX_RCU_H
25
26 #include <trace/events/rcu.h>
27 #ifdef CONFIG_RCU_TRACE
28 #define RCU_TRACE(stmt) stmt
29 #else /* #ifdef CONFIG_RCU_TRACE */
30 #define RCU_TRACE(stmt)
31 #endif /* #else #ifdef CONFIG_RCU_TRACE */
32
33 /*
34 * Process-level increment to ->dynticks_nesting field. This allows for
35 * architectures that use half-interrupts and half-exceptions from
36 * process context.
37 *
38 * DYNTICK_TASK_NEST_MASK defines a field of width DYNTICK_TASK_NEST_WIDTH
39 * that counts the number of process-based reasons why RCU cannot
40 * consider the corresponding CPU to be idle, and DYNTICK_TASK_NEST_VALUE
41 * is the value used to increment or decrement this field.
42 *
43 * The rest of the bits could in principle be used to count interrupts,
44 * but this would mean that a negative-one value in the interrupt
45 * field could incorrectly zero out the DYNTICK_TASK_NEST_MASK field.
46 * We therefore provide a two-bit guard field defined by DYNTICK_TASK_MASK
47 * that is set to DYNTICK_TASK_FLAG upon initial exit from idle.
48 * The DYNTICK_TASK_EXIT_IDLE value is thus the combined value used upon
49 * initial exit from idle.
50 */
51 #define DYNTICK_TASK_NEST_WIDTH 7
52 #define DYNTICK_TASK_NEST_VALUE ((LLONG_MAX >> DYNTICK_TASK_NEST_WIDTH) + 1)
53 #define DYNTICK_TASK_NEST_MASK (LLONG_MAX - DYNTICK_TASK_NEST_VALUE + 1)
54 #define DYNTICK_TASK_FLAG ((DYNTICK_TASK_NEST_VALUE / 8) * 2)
55 #define DYNTICK_TASK_MASK ((DYNTICK_TASK_NEST_VALUE / 8) * 3)
56 #define DYNTICK_TASK_EXIT_IDLE (DYNTICK_TASK_NEST_VALUE + \
57 DYNTICK_TASK_FLAG)
58
59 /*
60 * debug_rcu_head_queue()/debug_rcu_head_unqueue() are used internally
61 * by call_rcu() and rcu callback execution, and are therefore not part of the
62 * RCU API. Leaving in rcupdate.h because they are used by all RCU flavors.
63 */
64
65 #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
66 # define STATE_RCU_HEAD_READY 0
67 # define STATE_RCU_HEAD_QUEUED 1
68
69 extern struct debug_obj_descr rcuhead_debug_descr;
70
debug_rcu_head_queue(struct rcu_head * head)71 static inline int debug_rcu_head_queue(struct rcu_head *head)
72 {
73 int r1;
74
75 r1 = debug_object_activate(head, &rcuhead_debug_descr);
76 debug_object_active_state(head, &rcuhead_debug_descr,
77 STATE_RCU_HEAD_READY,
78 STATE_RCU_HEAD_QUEUED);
79 return r1;
80 }
81
debug_rcu_head_unqueue(struct rcu_head * head)82 static inline void debug_rcu_head_unqueue(struct rcu_head *head)
83 {
84 debug_object_active_state(head, &rcuhead_debug_descr,
85 STATE_RCU_HEAD_QUEUED,
86 STATE_RCU_HEAD_READY);
87 debug_object_deactivate(head, &rcuhead_debug_descr);
88 }
89 #else /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
debug_rcu_head_queue(struct rcu_head * head)90 static inline int debug_rcu_head_queue(struct rcu_head *head)
91 {
92 return 0;
93 }
94
debug_rcu_head_unqueue(struct rcu_head * head)95 static inline void debug_rcu_head_unqueue(struct rcu_head *head)
96 {
97 }
98 #endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
99
100 void kfree(const void *);
101
102 /*
103 * Reclaim the specified callback, either by invoking it (non-lazy case)
104 * or freeing it directly (lazy case). Return true if lazy, false otherwise.
105 */
__rcu_reclaim(const char * rn,struct rcu_head * head)106 static inline bool __rcu_reclaim(const char *rn, struct rcu_head *head)
107 {
108 unsigned long offset = (unsigned long)head->func;
109
110 rcu_lock_acquire(&rcu_callback_map);
111 if (__is_kfree_rcu_offset(offset)) {
112 RCU_TRACE(trace_rcu_invoke_kfree_callback(rn, head, offset));
113 kfree((void *)head - offset);
114 rcu_lock_release(&rcu_callback_map);
115 return true;
116 } else {
117 RCU_TRACE(trace_rcu_invoke_callback(rn, head));
118 head->func(head);
119 rcu_lock_release(&rcu_callback_map);
120 return false;
121 }
122 }
123
124 #ifdef CONFIG_RCU_STALL_COMMON
125
126 extern int rcu_cpu_stall_suppress;
127 int rcu_jiffies_till_stall_check(void);
128
129 #endif /* #ifdef CONFIG_RCU_STALL_COMMON */
130
131 /*
132 * Strings used in tracepoints need to be exported via the
133 * tracing system such that tools like perf and trace-cmd can
134 * translate the string address pointers to actual text.
135 */
136 #define TPS(x) tracepoint_string(x)
137
138 #endif /* __LINUX_RCU_H */
139