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() preempt_enable_no_resched()
68 #define preempt_check_resched() do { } while (0)
71 #define preempt_disable_notrace() \
73 __preempt_count_inc(); \
77 #define preempt_enable_no_resched_notrace() \
80 __preempt_count_dec(); \
85 #ifndef CONFIG_CONTEXT_TRACKING
86 #define __preempt_schedule_context() __preempt_schedule()
89 #define preempt_enable_notrace() \
92 if (unlikely(__preempt_count_dec_and_test())) \
93 __preempt_schedule_context(); \
96 #define preempt_enable_notrace() preempt_enable_no_resched_notrace()
99 #else /* !CONFIG_PREEMPT_COUNT */
102 * Even if we don't have any preemption, we need preempt disable/enable
103 * to be barriers, so that we don't have things like get_user/put_user
104 * that can cause faults and scheduling migrate into our preempt-protected
107 #define preempt_disable() barrier()
108 #define sched_preempt_enable_no_resched() barrier()
109 #define preempt_enable_no_resched() barrier()
110 #define preempt_enable() barrier()
111 #define preempt_check_resched() do { } while (0)
113 #define preempt_disable_notrace() barrier()
114 #define preempt_enable_no_resched_notrace() barrier()
115 #define preempt_enable_notrace() barrier()
117 #endif /* CONFIG_PREEMPT_COUNT */
119 #ifdef CONFIG_PREEMPT_NOTIFIERS
121 struct preempt_notifier;
124 * preempt_ops - notifiers called when a task is preempted and rescheduled
125 * @sched_in: we're about to be rescheduled:
126 * notifier: struct preempt_notifier for the task being scheduled
127 * cpu: cpu we're scheduled on
128 * @sched_out: we've just been preempted
129 * notifier: struct preempt_notifier for the task being preempted
130 * next: the task that's kicking us out
132 * Please note that sched_in and out are called under different
133 * contexts. sched_out is called with rq lock held and irq disabled
134 * while sched_in is called without rq lock and irq enabled. This
135 * difference is intentional and depended upon by its users.
138 void (*sched_in)(struct preempt_notifier *notifier, int cpu);
139 void (*sched_out)(struct preempt_notifier *notifier,
140 struct task_struct *next);
144 * preempt_notifier - key for installing preemption notifiers
145 * @link: internal use
146 * @ops: defines the notifier functions to be called
148 * Usually used in conjunction with container_of().
150 struct preempt_notifier {
151 struct hlist_node link;
152 struct preempt_ops *ops;
155 void preempt_notifier_register(struct preempt_notifier *notifier);
156 void preempt_notifier_unregister(struct preempt_notifier *notifier);
158 static inline void preempt_notifier_init(struct preempt_notifier *notifier,
159 struct preempt_ops *ops)
161 INIT_HLIST_NODE(¬ifier->link);
167 #endif /* __LINUX_PREEMPT_H */