LXR linux/include/linux/preempt.h

   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#ifdef CONFIG_CONTEXT_TRACKING
  37
  38void preempt_schedule_context(void);
  39
  40#define preempt_check_resched_context() \
  41do { \
  42        if (unlikely(test_thread_flag(TIF_NEED_RESCHED))) \
  43                preempt_schedule_context(); \
  44} while (0)
  45#else
  46
  47#define preempt_check_resched_context() preempt_check_resched()
  48
  49#endif /* CONFIG_CONTEXT_TRACKING */
  50
  51#else /* !CONFIG_PREEMPT */
  52
  53#define preempt_check_resched()         do { } while (0)
  54#define preempt_check_resched_context() do { } while (0)
  55
  56#endif /* CONFIG_PREEMPT */
  57
  58
  59#ifdef CONFIG_PREEMPT_COUNT
  60
  61#define preempt_disable() \
  62do { \
  63        inc_preempt_count(); \
  64        barrier(); \
  65} while (0)
  66
  67#define sched_preempt_enable_no_resched() \
  68do { \
  69        barrier(); \
  70        dec_preempt_count(); \
  71} while (0)
  72
  73#define preempt_enable_no_resched()     sched_preempt_enable_no_resched()
  74
  75#define preempt_enable() \
  76do { \
  77        preempt_enable_no_resched(); \
  78        barrier(); \
  79        preempt_check_resched(); \
  80} while (0)
  81
  82/* For debugging and tracer internals only! */
  83#define add_preempt_count_notrace(val)                  \
  84        do { preempt_count() += (val); } while (0)
  85#define sub_preempt_count_notrace(val)                  \
  86        do { preempt_count() -= (val); } while (0)
  87#define inc_preempt_count_notrace() add_preempt_count_notrace(1)
  88#define dec_preempt_count_notrace() sub_preempt_count_notrace(1)
  89
  90#define preempt_disable_notrace() \
  91do { \
  92        inc_preempt_count_notrace(); \
  93        barrier(); \
  94} while (0)
  95
  96#define preempt_enable_no_resched_notrace() \
  97do { \
  98        barrier(); \
  99        dec_preempt_count_notrace(); \
 100} while (0)
 101
 102/* preempt_check_resched is OK to trace */
 103#define preempt_enable_notrace() \
 104do { \
 105        preempt_enable_no_resched_notrace(); \
 106        barrier(); \
 107        preempt_check_resched_context(); \
 108} while (0)
 109
 110#else /* !CONFIG_PREEMPT_COUNT */
 111
 112/*
 113 * Even if we don't have any preemption, we need preempt disable/enable
 114 * to be barriers, so that we don't have things like get_user/put_user
 115 * that can cause faults and scheduling migrate into our preempt-protected
 116 * region.
 117 */
 118#define preempt_disable()               barrier()
 119#define sched_preempt_enable_no_resched()       barrier()
 120#define preempt_enable_no_resched()     barrier()
 121#define preempt_enable()                barrier()
 122
 123#define preempt_disable_notrace()               barrier()
 124#define preempt_enable_no_resched_notrace()     barrier()
 125#define preempt_enable_notrace()                barrier()
 126
 127#endif /* CONFIG_PREEMPT_COUNT */
 128
 129#ifdef CONFIG_PREEMPT_NOTIFIERS
 130
 131struct preempt_notifier;
 132
 133/**
 134 * preempt_ops - notifiers called when a task is preempted and rescheduled
 135 * @sched_in: we're about to be rescheduled:
 136 *    notifier: struct preempt_notifier for the task being scheduled
 137 *    cpu:  cpu we're scheduled on
 138 * @sched_out: we've just been preempted
 139 *    notifier: struct preempt_notifier for the task being preempted
 140 *    next: the task that's kicking us out
 141 *
 142 * Please note that sched_in and out are called under different
 143 * contexts.  sched_out is called with rq lock held and irq disabled
 144 * while sched_in is called without rq lock and irq enabled.  This
 145 * difference is intentional and depended upon by its users.
 146 */
 147struct preempt_ops {
 148        void (*sched_in)(struct preempt_notifier *notifier, int cpu);
 149        void (*sched_out)(struct preempt_notifier *notifier,
 150                          struct task_struct *next);
 151};
 152
 153/**
 154 * preempt_notifier - key for installing preemption notifiers
 155 * @link: internal use
 156 * @ops: defines the notifier functions to be called
 157 *
 158 * Usually used in conjunction with container_of().
 159 */
 160struct preempt_notifier {
 161        struct hlist_node link;
 162        struct preempt_ops *ops;
 163};
 164
 165void preempt_notifier_register(struct preempt_notifier *notifier);
 166void preempt_notifier_unregister(struct preempt_notifier *notifier);
 167
 168static inline void preempt_notifier_init(struct preempt_notifier *notifier,
 169                                     struct preempt_ops *ops)
 170{
 171        INIT_HLIST_NODE(&notifier->link);
 172        notifier->ops = ops;
 173}
 174
 175#endif
 176
 177#endif /* __LINUX_PREEMPT_H */
 178