Linux Kernel  3.7.1
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rcu.h
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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, write to the Free Software
16  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
17  *
18  * Copyright IBM Corporation, 2011
19  *
20  * Author: Paul E. McKenney <[email protected]>
21  */
22 
23 #ifndef __LINUX_RCU_H
24 #define __LINUX_RCU_H
25 
26 #ifdef CONFIG_RCU_TRACE
27 #define RCU_TRACE(stmt) stmt
28 #else /* #ifdef CONFIG_RCU_TRACE */
29 #define RCU_TRACE(stmt)
30 #endif /* #else #ifdef CONFIG_RCU_TRACE */
31 
32 /*
33  * Process-level increment to ->dynticks_nesting field. This allows for
34  * architectures that use half-interrupts and half-exceptions from
35  * process context.
36  *
37  * DYNTICK_TASK_NEST_MASK defines a field of width DYNTICK_TASK_NEST_WIDTH
38  * that counts the number of process-based reasons why RCU cannot
39  * consider the corresponding CPU to be idle, and DYNTICK_TASK_NEST_VALUE
40  * is the value used to increment or decrement this field.
41  *
42  * The rest of the bits could in principle be used to count interrupts,
43  * but this would mean that a negative-one value in the interrupt
44  * field could incorrectly zero out the DYNTICK_TASK_NEST_MASK field.
45  * We therefore provide a two-bit guard field defined by DYNTICK_TASK_MASK
46  * that is set to DYNTICK_TASK_FLAG upon initial exit from idle.
47  * The DYNTICK_TASK_EXIT_IDLE value is thus the combined value used upon
48  * initial exit from idle.
49  */
50 #define DYNTICK_TASK_NEST_WIDTH 7
51 #define DYNTICK_TASK_NEST_VALUE ((LLONG_MAX >> DYNTICK_TASK_NEST_WIDTH) + 1)
52 #define DYNTICK_TASK_NEST_MASK (LLONG_MAX - DYNTICK_TASK_NEST_VALUE + 1)
53 #define DYNTICK_TASK_FLAG ((DYNTICK_TASK_NEST_VALUE / 8) * 2)
54 #define DYNTICK_TASK_MASK ((DYNTICK_TASK_NEST_VALUE / 8) * 3)
55 #define DYNTICK_TASK_EXIT_IDLE (DYNTICK_TASK_NEST_VALUE + \
56  DYNTICK_TASK_FLAG)
57 
58 /*
59  * debug_rcu_head_queue()/debug_rcu_head_unqueue() are used internally
60  * by call_rcu() and rcu callback execution, and are therefore not part of the
61  * RCU API. Leaving in rcupdate.h because they are used by all RCU flavors.
62  */
63 
64 #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
65 # define STATE_RCU_HEAD_READY 0
66 # define STATE_RCU_HEAD_QUEUED 1
67 
68 extern struct debug_obj_descr rcuhead_debug_descr;
69 
70 static inline void debug_rcu_head_queue(struct rcu_head *head)
71 {
72  debug_object_activate(head, &rcuhead_debug_descr);
73  debug_object_active_state(head, &rcuhead_debug_descr,
74  STATE_RCU_HEAD_READY,
75  STATE_RCU_HEAD_QUEUED);
76 }
77 
78 static inline void debug_rcu_head_unqueue(struct rcu_head *head)
79 {
80  debug_object_active_state(head, &rcuhead_debug_descr,
81  STATE_RCU_HEAD_QUEUED,
82  STATE_RCU_HEAD_READY);
83  debug_object_deactivate(head, &rcuhead_debug_descr);
84 }
85 #else /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
86 static inline void debug_rcu_head_queue(struct rcu_head *head)
87 {
88 }
89 
90 static inline void debug_rcu_head_unqueue(struct rcu_head *head)
91 {
92 }
93 #endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
94 
95 extern void kfree(const void *);
96 
97 static inline bool __rcu_reclaim(char *rn, struct rcu_head *head)
98 {
99  unsigned long offset = (unsigned long)head->func;
100 
101  if (__is_kfree_rcu_offset(offset)) {
102  RCU_TRACE(trace_rcu_invoke_kfree_callback(rn, head, offset));
103  kfree((void *)head - offset);
104  return 1;
105  } else {
107  head->func(head);
108  return 0;
109  }
110 }
111 
112 #endif /* __LINUX_RCU_H */