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 #ifdef CONFIG_DEBUG_PREEMPT
  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_disable() \
  31 do { \
  32         inc_preempt_count(); \
  33         barrier(); \
  34 } while (0)
  35
  36 #define preempt_enable_no_resched() \
  37 do { \
  38         barrier(); \
  39         dec_preempt_count(); \
  40 } while (0)
  41
  42 #define preempt_check_resched() \
  43 do { \
  44         if (unlikely(test_thread_flag(TIF_NEED_RESCHED))) \
  45                 preempt_schedule(); \
  46 } while (0)
  47
  48 #define preempt_enable() \
  49 do { \
  50         preempt_enable_no_resched(); \
  51         barrier(); \
  52         preempt_check_resched(); \
  53 } while (0)
  54
  55 #else
  56
  57 #define preempt_disable()               do { } while (0)
  58 #define preempt_enable_no_resched()     do { } while (0)
  59 #define preempt_enable()                do { } while (0)
  60 #define preempt_check_resched()         do { } while (0)
  61
  62 #endif
  63
  64 #ifdef CONFIG_PREEMPT_NOTIFIERS
  65
  66 struct preempt_notifier;
  67
  68 /**
  69  * preempt_ops - notifiers called when a task is preempted and rescheduled
  70  * @sched_in: we're about to be rescheduled:
  71  *    notifier: struct preempt_notifier for the task being scheduled
  72  *    cpu:  cpu we're scheduled on
  73  * @sched_out: we've just been preempted
  74  *    notifier: struct preempt_notifier for the task being preempted
  75  *    next: the task that's kicking us out
  76  */
  77 struct preempt_ops {
  78         void (*sched_in)(struct preempt_notifier *notifier, int cpu);
  79         void (*sched_out)(struct preempt_notifier *notifier,
  80                           struct task_struct *next);
  81 };
  82
  83 /**
  84  * preempt_notifier - key for installing preemption notifiers
  85  * @link: internal use
  86  * @ops: defines the notifier functions to be called
  87  *
  88  * Usually used in conjunction with container_of().
  89  */
  90 struct preempt_notifier {
  91         struct hlist_node link;
  92         struct preempt_ops *ops;
  93 };
  94
  95 void preempt_notifier_register(struct preempt_notifier *notifier);
  96 void preempt_notifier_unregister(struct preempt_notifier *notifier);
  97
  98 static inline void preempt_notifier_init(struct preempt_notifier *notifier,
  99                                      struct preempt_ops *ops)
 100 {
 101         INIT_HLIST_NODE(&notifier->link);
 102         notifier->ops = ops;
 103 }
 104
 105 #endif
 106
 107 #endif /* __LINUX_PREEMPT_H */