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 #ifdef CONFIG_CONTEXT_TRACKING
  37
  38 void preempt_schedule_context(void);
  39
  40 #define preempt_check_resched_context() \
  41 do { \
  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() \
  62 do { \
  63         inc_preempt_count(); \
  64         barrier(); \
  65 } while (0)
  66
  67 #define sched_preempt_enable_no_resched() \
  68 do { \
  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() \
  76 do { \
  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() \
  91 do { \
  92         inc_preempt_count_notrace(); \
  93         barrier(); \
  94 } while (0)
  95
  96 #define preempt_enable_no_resched_notrace() \
  97 do { \
  98         barrier(); \
  99         dec_preempt_count_notrace(); \
 100 } while (0)
 101
 102 /* preempt_check_resched is OK to trace */
 103 #define preempt_enable_notrace() \
 104 do { \
 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
 131 struct 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  */
 147 struct 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  */
 160 struct preempt_notifier {
 161         struct hlist_node link;
 162         struct preempt_ops *ops;
 163 };
 164
 165 void preempt_notifier_register(struct preempt_notifier *notifier);
 166 void preempt_notifier_unregister(struct preempt_notifier *notifier);
 167
 168 static 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 */