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 preempt_enable_no_resched() \
  52 do { \
  53         barrier(); \
  54         dec_preempt_count(); \
  55 } while (0)
  56
  57 #define preempt_enable() \
  58 do { \
  59         preempt_enable_no_resched(); \
  60         barrier(); \
  61         preempt_check_resched(); \
  62 } while (0)
  63
  64 /* For debugging and tracer internals only! */
  65 #define add_preempt_count_notrace(val)                  \
  66         do { preempt_count() += (val); } while (0)
  67 #define sub_preempt_count_notrace(val)                  \
  68         do { preempt_count() -= (val); } while (0)
  69 #define inc_preempt_count_notrace() add_preempt_count_notrace(1)
  70 #define dec_preempt_count_notrace() sub_preempt_count_notrace(1)
  71
  72 #define preempt_disable_notrace() \
  73 do { \
  74         inc_preempt_count_notrace(); \
  75         barrier(); \
  76 } while (0)
  77
  78 #define preempt_enable_no_resched_notrace() \
  79 do { \
  80         barrier(); \
  81         dec_preempt_count_notrace(); \
  82 } while (0)
  83
  84 /* preempt_check_resched is OK to trace */
  85 #define preempt_enable_notrace() \
  86 do { \
  87         preempt_enable_no_resched_notrace(); \
  88         barrier(); \
  89         preempt_check_resched(); \
  90 } while (0)
  91
  92 #else /* !CONFIG_PREEMPT_COUNT */
  93
  94 #define preempt_disable()               do { } while (0)
  95 #define preempt_enable_no_resched()     do { } while (0)
  96 #define preempt_enable()                do { } while (0)
  97
  98 #define preempt_disable_notrace()               do { } while (0)
  99 #define preempt_enable_no_resched_notrace()     do { } while (0)
 100 #define preempt_enable_notrace()                do { } while (0)
 101
 102 #endif /* CONFIG_PREEMPT_COUNT */
 103
 104 #ifdef CONFIG_PREEMPT_NOTIFIERS
 105
 106 struct preempt_notifier;
 107
 108 /**
 109  * preempt_ops - notifiers called when a task is preempted and rescheduled
 110  * @sched_in: we're about to be rescheduled:
 111  *    notifier: struct preempt_notifier for the task being scheduled
 112  *    cpu:  cpu we're scheduled on
 113  * @sched_out: we've just been preempted
 114  *    notifier: struct preempt_notifier for the task being preempted
 115  *    next: the task that's kicking us out
 116  *
 117  * Please note that sched_in and out are called under different
 118  * contexts.  sched_out is called with rq lock held and irq disabled
 119  * while sched_in is called without rq lock and irq enabled.  This
 120  * difference is intentional and depended upon by its users.
 121  */
 122 struct preempt_ops {
 123         void (*sched_in)(struct preempt_notifier *notifier, int cpu);
 124         void (*sched_out)(struct preempt_notifier *notifier,
 125                           struct task_struct *next);
 126 };
 127
 128 /**
 129  * preempt_notifier - key for installing preemption notifiers
 130  * @link: internal use
 131  * @ops: defines the notifier functions to be called
 132  *
 133  * Usually used in conjunction with container_of().
 134  */
 135 struct preempt_notifier {
 136         struct hlist_node link;
 137         struct preempt_ops *ops;
 138 };
 139
 140 void preempt_notifier_register(struct preempt_notifier *notifier);
 141 void preempt_notifier_unregister(struct preempt_notifier *notifier);
 142
 143 static inline void preempt_notifier_init(struct preempt_notifier *notifier,
 144                                      struct preempt_ops *ops)
 145 {
 146         INIT_HLIST_NODE(&notifier->link);
 147         notifier->ops = ops;
 148 }
 149
 150 #endif
 151
 152 #endif /* __LINUX_PREEMPT_H */