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