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
  28 asmlinkage void preempt_schedule(void);
  29
  30 #define preempt_check_resched() \
  31 do { \
  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() \
  46 do { \
  47         inc_preempt_count(); \
  48         barrier(); \
  49 } while (0)
  50
  51 #define sched_preempt_enable_no_resched() \
  52 do { \
  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() \
  60 do { \
  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() \
  75 do { \
  76         inc_preempt_count_notrace(); \
  77         barrier(); \
  78 } while (0)
  79
  80 #define preempt_enable_no_resched_notrace() \
  81 do { \
  82         barrier(); \
  83         dec_preempt_count_notrace(); \
  84 } while (0)
  85
  86 /* preempt_check_resched is OK to trace */
  87 #define preempt_enable_notrace() \
  88 do { \
  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
 115 struct 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  */
 131 struct 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  */
 144 struct preempt_notifier {
 145         struct hlist_node link;
 146         struct preempt_ops *ops;
 147 };
 148
 149 void preempt_notifier_register(struct preempt_notifier *notifier);
 150 void preempt_notifier_unregister(struct preempt_notifier *notifier);
 151
 152 static 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 */