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_disable() \
31 do { \
32 	inc_preempt_count(); \
33 	barrier(); \
34 } while (0)
35 
36 #define preempt_enable_no_resched() \
37 do { \
38 	barrier(); \
39 	dec_preempt_count(); \
40 } while (0)
41 
42 #define preempt_check_resched() \
43 do { \
44 	if (unlikely(test_thread_flag(TIF_NEED_RESCHED))) \
45 		preempt_schedule(); \
46 } while (0)
47 
48 #define preempt_enable() \
49 do { \
50 	preempt_enable_no_resched(); \
51 	barrier(); \
52 	preempt_check_resched(); \
53 } while (0)
54 
55 /* For debugging and tracer internals only! */
56 #define add_preempt_count_notrace(val)			\
57 	do { preempt_count() += (val); } while (0)
58 #define sub_preempt_count_notrace(val)			\
59 	do { preempt_count() -= (val); } while (0)
60 #define inc_preempt_count_notrace() add_preempt_count_notrace(1)
61 #define dec_preempt_count_notrace() sub_preempt_count_notrace(1)
62 
63 #define preempt_disable_notrace() \
64 do { \
65 	inc_preempt_count_notrace(); \
66 	barrier(); \
67 } while (0)
68 
69 #define preempt_enable_no_resched_notrace() \
70 do { \
71 	barrier(); \
72 	dec_preempt_count_notrace(); \
73 } while (0)
74 
75 /* preempt_check_resched is OK to trace */
76 #define preempt_enable_notrace() \
77 do { \
78 	preempt_enable_no_resched_notrace(); \
79 	barrier(); \
80 	preempt_check_resched(); \
81 } while (0)
82 
83 #else
84 
85 #define preempt_disable()		do { } while (0)
86 #define preempt_enable_no_resched()	do { } while (0)
87 #define preempt_enable()		do { } while (0)
88 #define preempt_check_resched()		do { } while (0)
89 
90 #define preempt_disable_notrace()		do { } while (0)
91 #define preempt_enable_no_resched_notrace()	do { } while (0)
92 #define preempt_enable_notrace()		do { } while (0)
93 
94 #endif
95 
96 #ifdef CONFIG_PREEMPT_NOTIFIERS
97 
98 struct preempt_notifier;
99 
100 /**
101  * preempt_ops - notifiers called when a task is preempted and rescheduled
102  * @sched_in: we're about to be rescheduled:
103  *    notifier: struct preempt_notifier for the task being scheduled
104  *    cpu:  cpu we're scheduled on
105  * @sched_out: we've just been preempted
106  *    notifier: struct preempt_notifier for the task being preempted
107  *    next: the task that's kicking us out
108  *
109  * Please note that sched_in and out are called under different
110  * contexts.  sched_out is called with rq lock held and irq disabled
111  * while sched_in is called without rq lock and irq enabled.  This
112  * difference is intentional and depended upon by its users.
113  */
114 struct preempt_ops {
115 	void (*sched_in)(struct preempt_notifier *notifier, int cpu);
116 	void (*sched_out)(struct preempt_notifier *notifier,
117 			  struct task_struct *next);
118 };
119 
120 /**
121  * preempt_notifier - key for installing preemption notifiers
122  * @link: internal use
123  * @ops: defines the notifier functions to be called
124  *
125  * Usually used in conjunction with container_of().
126  */
127 struct preempt_notifier {
128 	struct hlist_node link;
129 	struct preempt_ops *ops;
130 };
131 
132 void preempt_notifier_register(struct preempt_notifier *notifier);
133 void preempt_notifier_unregister(struct preempt_notifier *notifier);
134 
preempt_notifier_init(struct preempt_notifier * notifier,struct preempt_ops * ops)135 static inline void preempt_notifier_init(struct preempt_notifier *notifier,
136 				     struct preempt_ops *ops)
137 {
138 	INIT_HLIST_NODE(&notifier->link);
139 	notifier->ops = ops;
140 }
141 
142 #endif
143 
144 #endif /* __LINUX_PREEMPT_H */
145