1 #ifndef __LINUX_PREEMPT_H
2 #define __LINUX_PREEMPT_H
5 * include/linux/preempt.h - macros for accessing and manipulating
6 * preempt_count (used for kernel preemption, interrupt count, etc.)
9 #include <linux/linkage.h>
10 #include <linux/list.h>
13 * We use the MSB mostly because its available; see <linux/preempt_mask.h> for
14 * the other bits -- can't include that header due to inclusion hell.
16 #define PREEMPT_NEED_RESCHED 0x80000000
18 #include <asm/preempt.h>
20 #if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_PREEMPT_TRACER)
21 extern void preempt_count_add(int val);
22 extern void preempt_count_sub(int val);
23 #define preempt_count_dec_and_test() ({ preempt_count_sub(1); should_resched(); })
25 #define preempt_count_add(val) __preempt_count_add(val)
26 #define preempt_count_sub(val) __preempt_count_sub(val)
27 #define preempt_count_dec_and_test() __preempt_count_dec_and_test()
30 #define __preempt_count_inc() __preempt_count_add(1)
31 #define __preempt_count_dec() __preempt_count_sub(1)
33 #define preempt_count_inc() preempt_count_add(1)
34 #define preempt_count_dec() preempt_count_sub(1)
36 #ifdef CONFIG_PREEMPT_COUNT
38 #define preempt_disable() \
40 preempt_count_inc(); \
44 #define sched_preempt_enable_no_resched() \
47 preempt_count_dec(); \
50 #define preempt_enable_no_resched() sched_preempt_enable_no_resched()
53 #define preempt_enable() \
56 if (unlikely(preempt_count_dec_and_test())) \
57 __preempt_schedule(); \
60 #define preempt_check_resched() \
62 if (should_resched()) \
63 __preempt_schedule(); \
67 #define preempt_enable() \
70 preempt_count_dec(); \
72 #define preempt_check_resched() do { } while (0)
75 #define preempt_disable_notrace() \
77 __preempt_count_inc(); \
81 #define preempt_enable_no_resched_notrace() \
84 __preempt_count_dec(); \
89 #ifndef CONFIG_CONTEXT_TRACKING
90 #define __preempt_schedule_context() __preempt_schedule()
93 #define preempt_enable_notrace() \
96 if (unlikely(__preempt_count_dec_and_test())) \
97 __preempt_schedule_context(); \
100 #define preempt_enable_notrace() \
103 __preempt_count_dec(); \
107 #else /* !CONFIG_PREEMPT_COUNT */
110 * Even if we don't have any preemption, we need preempt disable/enable
111 * to be barriers, so that we don't have things like get_user/put_user
112 * that can cause faults and scheduling migrate into our preempt-protected
115 #define preempt_disable() barrier()
116 #define sched_preempt_enable_no_resched() barrier()
117 #define preempt_enable_no_resched() barrier()
118 #define preempt_enable() barrier()
119 #define preempt_check_resched() do { } while (0)
121 #define preempt_disable_notrace() barrier()
122 #define preempt_enable_no_resched_notrace() barrier()
123 #define preempt_enable_notrace() barrier()
125 #endif /* CONFIG_PREEMPT_COUNT */
129 * Modules have no business playing preemption tricks.
131 #undef sched_preempt_enable_no_resched
132 #undef preempt_enable_no_resched
133 #undef preempt_enable_no_resched_notrace
134 #undef preempt_check_resched
137 #ifdef CONFIG_PREEMPT_NOTIFIERS
139 struct preempt_notifier;
142 * preempt_ops - notifiers called when a task is preempted and rescheduled
143 * @sched_in: we're about to be rescheduled:
144 * notifier: struct preempt_notifier for the task being scheduled
145 * cpu: cpu we're scheduled on
146 * @sched_out: we've just been preempted
147 * notifier: struct preempt_notifier for the task being preempted
148 * next: the task that's kicking us out
150 * Please note that sched_in and out are called under different
151 * contexts. sched_out is called with rq lock held and irq disabled
152 * while sched_in is called without rq lock and irq enabled. This
153 * difference is intentional and depended upon by its users.
156 void (*sched_in)(struct preempt_notifier *notifier, int cpu);
157 void (*sched_out)(struct preempt_notifier *notifier,
158 struct task_struct *next);
162 * preempt_notifier - key for installing preemption notifiers
163 * @link: internal use
164 * @ops: defines the notifier functions to be called
166 * Usually used in conjunction with container_of().
168 struct preempt_notifier {
169 struct hlist_node link;
170 struct preempt_ops *ops;
173 void preempt_notifier_register(struct preempt_notifier *notifier);
174 void preempt_notifier_unregister(struct preempt_notifier *notifier);
176 static inline void preempt_notifier_init(struct preempt_notifier *notifier,
177 struct preempt_ops *ops)
179 INIT_HLIST_NODE(¬ifier->link);
185 #endif /* __LINUX_PREEMPT_H */