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 #define tif_need_resched() test_thread_flag(TIF_NEED_RESCHED)
20 #include <asm/preempt.h>
22 #if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_PREEMPT_TRACER)
23 extern void preempt_count_add(int val);
24 extern void preempt_count_sub(int val);
25 #define preempt_count_dec_and_test() ({ preempt_count_sub(1); should_resched(); })
27 #define preempt_count_add(val) __preempt_count_add(val)
28 #define preempt_count_sub(val) __preempt_count_sub(val)
29 #define preempt_count_dec_and_test() __preempt_count_dec_and_test()
32 #define __preempt_count_inc() __preempt_count_add(1)
33 #define __preempt_count_dec() __preempt_count_sub(1)
35 #define preempt_count_inc() preempt_count_add(1)
36 #define preempt_count_dec() preempt_count_sub(1)
38 #ifdef CONFIG_PREEMPT_COUNT
40 #define preempt_disable() \
42 preempt_count_inc(); \
46 #define sched_preempt_enable_no_resched() \
49 preempt_count_dec(); \
52 #define preempt_enable_no_resched() sched_preempt_enable_no_resched()
55 #define preempt_enable() \
58 if (unlikely(preempt_count_dec_and_test())) \
59 __preempt_schedule(); \
62 #define preempt_check_resched() \
64 if (should_resched()) \
65 __preempt_schedule(); \
69 #define preempt_enable() \
72 preempt_count_dec(); \
74 #define preempt_check_resched() do { } while (0)
77 #define preempt_disable_notrace() \
79 __preempt_count_inc(); \
83 #define preempt_enable_no_resched_notrace() \
86 __preempt_count_dec(); \
91 #ifndef CONFIG_CONTEXT_TRACKING
92 #define __preempt_schedule_context() __preempt_schedule()
95 #define preempt_enable_notrace() \
98 if (unlikely(__preempt_count_dec_and_test())) \
99 __preempt_schedule_context(); \
102 #define preempt_enable_notrace() \
105 __preempt_count_dec(); \
109 #else /* !CONFIG_PREEMPT_COUNT */
112 * Even if we don't have any preemption, we need preempt disable/enable
113 * to be barriers, so that we don't have things like get_user/put_user
114 * that can cause faults and scheduling migrate into our preempt-protected
117 #define preempt_disable() barrier()
118 #define sched_preempt_enable_no_resched() barrier()
119 #define preempt_enable_no_resched() barrier()
120 #define preempt_enable() barrier()
121 #define preempt_check_resched() do { } while (0)
123 #define preempt_disable_notrace() barrier()
124 #define preempt_enable_no_resched_notrace() barrier()
125 #define preempt_enable_notrace() barrier()
127 #endif /* CONFIG_PREEMPT_COUNT */
131 * Modules have no business playing preemption tricks.
133 #undef sched_preempt_enable_no_resched
134 #undef preempt_enable_no_resched
135 #undef preempt_enable_no_resched_notrace
136 #undef preempt_check_resched
139 #define preempt_set_need_resched() \
141 set_preempt_need_resched(); \
143 #define preempt_fold_need_resched() \
145 if (tif_need_resched()) \
146 set_preempt_need_resched(); \
149 #ifdef CONFIG_PREEMPT_NOTIFIERS
151 struct preempt_notifier;
154 * preempt_ops - notifiers called when a task is preempted and rescheduled
155 * @sched_in: we're about to be rescheduled:
156 * notifier: struct preempt_notifier for the task being scheduled
157 * cpu: cpu we're scheduled on
158 * @sched_out: we've just been preempted
159 * notifier: struct preempt_notifier for the task being preempted
160 * next: the task that's kicking us out
162 * Please note that sched_in and out are called under different
163 * contexts. sched_out is called with rq lock held and irq disabled
164 * while sched_in is called without rq lock and irq enabled. This
165 * difference is intentional and depended upon by its users.
168 void (*sched_in)(struct preempt_notifier *notifier, int cpu);
169 void (*sched_out)(struct preempt_notifier *notifier,
170 struct task_struct *next);
174 * preempt_notifier - key for installing preemption notifiers
175 * @link: internal use
176 * @ops: defines the notifier functions to be called
178 * Usually used in conjunction with container_of().
180 struct preempt_notifier {
181 struct hlist_node link;
182 struct preempt_ops *ops;
185 void preempt_notifier_register(struct preempt_notifier *notifier);
186 void preempt_notifier_unregister(struct preempt_notifier *notifier);
188 static inline void preempt_notifier_init(struct preempt_notifier *notifier,
189 struct preempt_ops *ops)
191 INIT_HLIST_NODE(¬ifier->link);
197 #endif /* __LINUX_PREEMPT_H */