linux/include/linux/preempt.h
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   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
  28asmlinkage void preempt_schedule(void);
  29
  30#define preempt_check_resched() \
  31do { \
  32        if (unlikely(test_thread_flag(TIF_NEED_RESCHED))) \
  33                preempt_schedule(); \
  34} while (0)
  35
  36#else /* !CONFIG_PREEMPT */
  37
  38#define preempt_check_resched()         do { } while (0)
  39
  40#endif /* CONFIG_PREEMPT */
  41
  42
  43#ifdef CONFIG_PREEMPT_COUNT
  44
  45#define preempt_disable() \
  46do { \
  47        inc_preempt_count(); \
  48        barrier(); \
  49} while (0)
  50
  51#define sched_preempt_enable_no_resched() \
  52do { \
  53        barrier(); \
  54        dec_preempt_count(); \
  55} while (0)
  56
  57#define preempt_enable_no_resched()     sched_preempt_enable_no_resched()
  58
  59#define preempt_enable() \
  60do { \
  61        preempt_enable_no_resched(); \
  62        barrier(); \
  63        preempt_check_resched(); \
  64} while (0)
  65
  66/* For debugging and tracer internals only! */
  67#define add_preempt_count_notrace(val)                  \
  68        do { preempt_count() += (val); } while (0)
  69#define sub_preempt_count_notrace(val)                  \
  70        do { preempt_count() -= (val); } while (0)
  71#define inc_preempt_count_notrace() add_preempt_count_notrace(1)
  72#define dec_preempt_count_notrace() sub_preempt_count_notrace(1)
  73
  74#define preempt_disable_notrace() \
  75do { \
  76        inc_preempt_count_notrace(); \
  77        barrier(); \
  78} while (0)
  79
  80#define preempt_enable_no_resched_notrace() \
  81do { \
  82        barrier(); \
  83        dec_preempt_count_notrace(); \
  84} while (0)
  85
  86/* preempt_check_resched is OK to trace */
  87#define preempt_enable_notrace() \
  88do { \
  89        preempt_enable_no_resched_notrace(); \
  90        barrier(); \
  91        preempt_check_resched(); \
  92} while (0)
  93
  94#else /* !CONFIG_PREEMPT_COUNT */
  95
  96/*
  97 * Even if we don't have any preemption, we need preempt disable/enable
  98 * to be barriers, so that we don't have things like get_user/put_user
  99 * that can cause faults and scheduling migrate into our preempt-protected
 100 * region.
 101 */
 102#define preempt_disable()               barrier()
 103#define sched_preempt_enable_no_resched()       barrier()
 104#define preempt_enable_no_resched()     barrier()
 105#define preempt_enable()                barrier()
 106
 107#define preempt_disable_notrace()               barrier()
 108#define preempt_enable_no_resched_notrace()     barrier()
 109#define preempt_enable_notrace()                barrier()
 110
 111#endif /* CONFIG_PREEMPT_COUNT */
 112
 113#ifdef CONFIG_PREEMPT_NOTIFIERS
 114
 115struct preempt_notifier;
 116
 117/**
 118 * preempt_ops - notifiers called when a task is preempted and rescheduled
 119 * @sched_in: we're about to be rescheduled:
 120 *    notifier: struct preempt_notifier for the task being scheduled
 121 *    cpu:  cpu we're scheduled on
 122 * @sched_out: we've just been preempted
 123 *    notifier: struct preempt_notifier for the task being preempted
 124 *    next: the task that's kicking us out
 125 *
 126 * Please note that sched_in and out are called under different
 127 * contexts.  sched_out is called with rq lock held and irq disabled
 128 * while sched_in is called without rq lock and irq enabled.  This
 129 * difference is intentional and depended upon by its users.
 130 */
 131struct preempt_ops {
 132        void (*sched_in)(struct preempt_notifier *notifier, int cpu);
 133        void (*sched_out)(struct preempt_notifier *notifier,
 134                          struct task_struct *next);
 135};
 136
 137/**
 138 * preempt_notifier - key for installing preemption notifiers
 139 * @link: internal use
 140 * @ops: defines the notifier functions to be called
 141 *
 142 * Usually used in conjunction with container_of().
 143 */
 144struct preempt_notifier {
 145        struct hlist_node link;
 146        struct preempt_ops *ops;
 147};
 148
 149void preempt_notifier_register(struct preempt_notifier *notifier);
 150void preempt_notifier_unregister(struct preempt_notifier *notifier);
 151
 152static inline void preempt_notifier_init(struct preempt_notifier *notifier,
 153                                     struct preempt_ops *ops)
 154{
 155        INIT_HLIST_NODE(&notifier->link);
 156        notifier->ops = ops;
 157}
 158
 159#endif
 160
 161#endif /* __LINUX_PREEMPT_H */
 162
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