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() \
24 ({ preempt_count_sub(1); should_resched(0); })
26 #define preempt_count_add(val) __preempt_count_add(val)
27 #define preempt_count_sub(val) __preempt_count_sub(val)
28 #define preempt_count_dec_and_test() __preempt_count_dec_and_test()
31 #define __preempt_count_inc() __preempt_count_add(1)
32 #define __preempt_count_dec() __preempt_count_sub(1)
34 #define preempt_count_inc() preempt_count_add(1)
35 #define preempt_count_dec() preempt_count_sub(1)
37 #ifdef CONFIG_PREEMPT_COUNT
39 #define preempt_disable() \
41 preempt_count_inc(); \
45 #define sched_preempt_enable_no_resched() \
48 preempt_count_dec(); \
51 #define preempt_enable_no_resched() sched_preempt_enable_no_resched()
54 #define preempt_enable() \
57 if (unlikely(preempt_count_dec_and_test())) \
58 __preempt_schedule(); \
61 #define preempt_check_resched() \
63 if (should_resched(0)) \
64 __preempt_schedule(); \
68 #define preempt_enable() \
71 preempt_count_dec(); \
73 #define preempt_check_resched() do { } while (0)
76 #define preempt_disable_notrace() \
78 __preempt_count_inc(); \
82 #define preempt_enable_no_resched_notrace() \
85 __preempt_count_dec(); \
90 #ifndef CONFIG_CONTEXT_TRACKING
91 #define __preempt_schedule_context() __preempt_schedule()
94 #define preempt_enable_notrace() \
97 if (unlikely(__preempt_count_dec_and_test())) \
98 __preempt_schedule_context(); \
101 #define preempt_enable_notrace() \
104 __preempt_count_dec(); \
108 #else /* !CONFIG_PREEMPT_COUNT */
111 * Even if we don't have any preemption, we need preempt disable/enable
112 * to be barriers, so that we don't have things like get_user/put_user
113 * that can cause faults and scheduling migrate into our preempt-protected
116 #define preempt_disable() barrier()
117 #define sched_preempt_enable_no_resched() barrier()
118 #define preempt_enable_no_resched() barrier()
119 #define preempt_enable() barrier()
120 #define preempt_check_resched() do { } while (0)
122 #define preempt_disable_notrace() barrier()
123 #define preempt_enable_no_resched_notrace() barrier()
124 #define preempt_enable_notrace() barrier()
126 #endif /* CONFIG_PREEMPT_COUNT */
130 * Modules have no business playing preemption tricks.
132 #undef sched_preempt_enable_no_resched
133 #undef preempt_enable_no_resched
134 #undef preempt_enable_no_resched_notrace
135 #undef preempt_check_resched
138 #define preempt_set_need_resched() \
140 set_preempt_need_resched(); \
142 #define preempt_fold_need_resched() \
144 if (tif_need_resched()) \
145 set_preempt_need_resched(); \
148 #ifdef CONFIG_PREEMPT_NOTIFIERS
150 struct preempt_notifier;
153 * preempt_ops - notifiers called when a task is preempted and rescheduled
154 * @sched_in: we're about to be rescheduled:
155 * notifier: struct preempt_notifier for the task being scheduled
156 * cpu: cpu we're scheduled on
157 * @sched_out: we've just been preempted
158 * notifier: struct preempt_notifier for the task being preempted
159 * next: the task that's kicking us out
161 * Please note that sched_in and out are called under different
162 * contexts. sched_out is called with rq lock held and irq disabled
163 * while sched_in is called without rq lock and irq enabled. This
164 * difference is intentional and depended upon by its users.
167 void (*sched_in)(struct preempt_notifier *notifier, int cpu);
168 void (*sched_out)(struct preempt_notifier *notifier,
169 struct task_struct *next);
173 * preempt_notifier - key for installing preemption notifiers
174 * @link: internal use
175 * @ops: defines the notifier functions to be called
177 * Usually used in conjunction with container_of().
179 struct preempt_notifier {
180 struct hlist_node link;
181 struct preempt_ops *ops;
184 void preempt_notifier_register(struct preempt_notifier *notifier);
185 void preempt_notifier_unregister(struct preempt_notifier *notifier);
187 static inline void preempt_notifier_init(struct preempt_notifier *notifier,
188 struct preempt_ops *ops)
190 INIT_HLIST_NODE(¬ifier->link);
196 #endif /* __LINUX_PREEMPT_H */