1 #ifndef __LINUX_PREEMPT_H
2 #define __LINUX_PREEMPT_H
3 
4 /*
5  * include/linux/preempt.h - macros for accessing and manipulating
6  * preempt_count (used for kernel preemption, interrupt count, etc.)
7  */
8 
9 #include <linux/thread_info.h>
10 #include <linux/linkage.h>
11 #include <linux/list.h>
12 
13 #if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_PREEMPT_TRACER)
14   extern void add_preempt_count(int val);
15   extern void sub_preempt_count(int val);
16 #else
17 # define add_preempt_count(val)	do { preempt_count() += (val); } while (0)
18 # define sub_preempt_count(val)	do { preempt_count() -= (val); } while (0)
19 #endif
20 
21 #define inc_preempt_count() add_preempt_count(1)
22 #define dec_preempt_count() sub_preempt_count(1)
23 
24 #define preempt_count()	(current_thread_info()->preempt_count)
25 
26 #ifdef CONFIG_PREEMPT
27 
28 asmlinkage void preempt_schedule(void);
29 
30 #define preempt_check_resched() \
31 do { \
32 	if (unlikely(test_thread_flag(TIF_NEED_RESCHED))) \
33 		preempt_schedule(); \
34 } while (0)
35 
36 #else /* !CONFIG_PREEMPT */
37 
38 #define preempt_check_resched()		do { } while (0)
39 
40 #endif /* CONFIG_PREEMPT */
41 
42 
43 #ifdef CONFIG_PREEMPT_COUNT
44 
45 #define preempt_disable() \
46 do { \
47 	inc_preempt_count(); \
48 	barrier(); \
49 } while (0)
50 
51 #define sched_preempt_enable_no_resched() \
52 do { \
53 	barrier(); \
54 	dec_preempt_count(); \
55 } while (0)
56 
57 #define preempt_enable_no_resched()	sched_preempt_enable_no_resched()
58 
59 #define preempt_enable() \
60 do { \
61 	preempt_enable_no_resched(); \
62 	barrier(); \
63 	preempt_check_resched(); \
64 } while (0)
65 
66 /* For debugging and tracer internals only! */
67 #define add_preempt_count_notrace(val)			\
68 	do { preempt_count() += (val); } while (0)
69 #define sub_preempt_count_notrace(val)			\
70 	do { preempt_count() -= (val); } while (0)
71 #define inc_preempt_count_notrace() add_preempt_count_notrace(1)
72 #define dec_preempt_count_notrace() sub_preempt_count_notrace(1)
73 
74 #define preempt_disable_notrace() \
75 do { \
76 	inc_preempt_count_notrace(); \
77 	barrier(); \
78 } while (0)
79 
80 #define preempt_enable_no_resched_notrace() \
81 do { \
82 	barrier(); \
83 	dec_preempt_count_notrace(); \
84 } while (0)
85 
86 /* preempt_check_resched is OK to trace */
87 #define preempt_enable_notrace() \
88 do { \
89 	preempt_enable_no_resched_notrace(); \
90 	barrier(); \
91 	preempt_check_resched(); \
92 } while (0)
93 
94 #else /* !CONFIG_PREEMPT_COUNT */
95 
96 /*
97  * Even if we don't have any preemption, we need preempt disable/enable
98  * to be barriers, so that we don't have things like get_user/put_user
99  * that can cause faults and scheduling migrate into our preempt-protected
100  * region.
101  */
102 #define preempt_disable()		barrier()
103 #define sched_preempt_enable_no_resched()	barrier()
104 #define preempt_enable_no_resched()	barrier()
105 #define preempt_enable()		barrier()
106 
107 #define preempt_disable_notrace()		barrier()
108 #define preempt_enable_no_resched_notrace()	barrier()
109 #define preempt_enable_notrace()		barrier()
110 
111 #endif /* CONFIG_PREEMPT_COUNT */
112 
113 #ifdef CONFIG_PREEMPT_NOTIFIERS
114 
115 struct preempt_notifier;
116 
117 /**
118  * preempt_ops - notifiers called when a task is preempted and rescheduled
119  * @sched_in: we're about to be rescheduled:
120  *    notifier: struct preempt_notifier for the task being scheduled
121  *    cpu:  cpu we're scheduled on
122  * @sched_out: we've just been preempted
123  *    notifier: struct preempt_notifier for the task being preempted
124  *    next: the task that's kicking us out
125  *
126  * Please note that sched_in and out are called under different
127  * contexts.  sched_out is called with rq lock held and irq disabled
128  * while sched_in is called without rq lock and irq enabled.  This
129  * difference is intentional and depended upon by its users.
130  */
131 struct preempt_ops {
132 	void (*sched_in)(struct preempt_notifier *notifier, int cpu);
133 	void (*sched_out)(struct preempt_notifier *notifier,
134 			  struct task_struct *next);
135 };
136 
137 /**
138  * preempt_notifier - key for installing preemption notifiers
139  * @link: internal use
140  * @ops: defines the notifier functions to be called
141  *
142  * Usually used in conjunction with container_of().
143  */
144 struct preempt_notifier {
145 	struct hlist_node link;
146 	struct preempt_ops *ops;
147 };
148 
149 void preempt_notifier_register(struct preempt_notifier *notifier);
150 void preempt_notifier_unregister(struct preempt_notifier *notifier);
151 
preempt_notifier_init(struct preempt_notifier * notifier,struct preempt_ops * ops)152 static inline void preempt_notifier_init(struct preempt_notifier *notifier,
153 				     struct preempt_ops *ops)
154 {
155 	INIT_HLIST_NODE(&notifier->link);
156 	notifier->ops = ops;
157 }
158 
159 #endif
160 
161 #endif /* __LINUX_PREEMPT_H */
162