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/linkage.h>
  10 #include <linux/list.h>
  11
  12 /*
  13  * We use the MSB mostly because its available; see <linux/preempt_mask.h> for
  14  * the other bits -- can't include that header due to inclusion hell.
  15  */
  16 #define PREEMPT_NEED_RESCHED    0x80000000
  17
  18 #include <asm/preempt.h>
  19
  20 #if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_PREEMPT_TRACER)
  21 extern void preempt_count_add(int val);
  22 extern void preempt_count_sub(int val);
  23 #define preempt_count_dec_and_test() ({ preempt_count_sub(1); should_resched(); })
  24 #else
  25 #define preempt_count_add(val)  __preempt_count_add(val)
  26 #define preempt_count_sub(val)  __preempt_count_sub(val)
  27 #define preempt_count_dec_and_test() __preempt_count_dec_and_test()
  28 #endif
  29
  30 #define __preempt_count_inc() __preempt_count_add(1)
  31 #define __preempt_count_dec() __preempt_count_sub(1)
  32
  33 #define preempt_count_inc() preempt_count_add(1)
  34 #define preempt_count_dec() preempt_count_sub(1)
  35
  36 #ifdef CONFIG_PREEMPT_COUNT
  37
  38 #define preempt_disable() \
  39 do { \
  40         preempt_count_inc(); \
  41         barrier(); \
  42 } while (0)
  43
  44 #define sched_preempt_enable_no_resched() \
  45 do { \
  46         barrier(); \
  47         preempt_count_dec(); \
  48 } while (0)
  49
  50 #define preempt_enable_no_resched() sched_preempt_enable_no_resched()
  51
  52 #ifdef CONFIG_PREEMPT
  53 #define preempt_enable() \
  54 do { \
  55         barrier(); \
  56         if (unlikely(preempt_count_dec_and_test())) \
  57                 __preempt_schedule(); \
  58 } while (0)
  59
  60 #define preempt_check_resched() \
  61 do { \
  62         if (should_resched()) \
  63                 __preempt_schedule(); \
  64 } while (0)
  65
  66 #else
  67 #define preempt_enable() \
  68 do { \
  69         barrier(); \
  70         preempt_count_dec(); \
  71 } while (0)
  72 #define preempt_check_resched() do { } while (0)
  73 #endif
  74
  75 #define preempt_disable_notrace() \
  76 do { \
  77         __preempt_count_inc(); \
  78         barrier(); \
  79 } while (0)
  80
  81 #define preempt_enable_no_resched_notrace() \
  82 do { \
  83         barrier(); \
  84         __preempt_count_dec(); \
  85 } while (0)
  86
  87 #ifdef CONFIG_PREEMPT
  88
  89 #ifndef CONFIG_CONTEXT_TRACKING
  90 #define __preempt_schedule_context() __preempt_schedule()
  91 #endif
  92
  93 #define preempt_enable_notrace() \
  94 do { \
  95         barrier(); \
  96         if (unlikely(__preempt_count_dec_and_test())) \
  97                 __preempt_schedule_context(); \
  98 } while (0)
  99 #else
 100 #define preempt_enable_notrace() \
 101 do { \
 102         barrier(); \
 103         __preempt_count_dec(); \
 104 } while (0)
 105 #endif
 106
 107 #else /* !CONFIG_PREEMPT_COUNT */
 108
 109 /*
 110  * Even if we don't have any preemption, we need preempt disable/enable
 111  * to be barriers, so that we don't have things like get_user/put_user
 112  * that can cause faults and scheduling migrate into our preempt-protected
 113  * region.
 114  */
 115 #define preempt_disable()                       barrier()
 116 #define sched_preempt_enable_no_resched()       barrier()
 117 #define preempt_enable_no_resched()             barrier()
 118 #define preempt_enable()                        barrier()
 119 #define preempt_check_resched()                 do { } while (0)
 120
 121 #define preempt_disable_notrace()               barrier()
 122 #define preempt_enable_no_resched_notrace()     barrier()
 123 #define preempt_enable_notrace()                barrier()
 124
 125 #endif /* CONFIG_PREEMPT_COUNT */
 126
 127 #ifdef MODULE
 128 /*
 129  * Modules have no business playing preemption tricks.
 130  */
 131 #undef sched_preempt_enable_no_resched
 132 #undef preempt_enable_no_resched
 133 #undef preempt_enable_no_resched_notrace
 134 #undef preempt_check_resched
 135 #endif
 136
 137 #define preempt_set_need_resched() \
 138 do { \
 139         set_preempt_need_resched(); \
 140 } while (0)
 141 #define preempt_fold_need_resched() \
 142 do { \
 143         if (tif_need_resched()) \
 144                 set_preempt_need_resched(); \
 145 } while (0)
 146
 147 #ifdef CONFIG_PREEMPT_NOTIFIERS
 148
 149 struct preempt_notifier;
 150
 151 /**
 152  * preempt_ops - notifiers called when a task is preempted and rescheduled
 153  * @sched_in: we're about to be rescheduled:
 154  *    notifier: struct preempt_notifier for the task being scheduled
 155  *    cpu:  cpu we're scheduled on
 156  * @sched_out: we've just been preempted
 157  *    notifier: struct preempt_notifier for the task being preempted
 158  *    next: the task that's kicking us out
 159  *
 160  * Please note that sched_in and out are called under different
 161  * contexts.  sched_out is called with rq lock held and irq disabled
 162  * while sched_in is called without rq lock and irq enabled.  This
 163  * difference is intentional and depended upon by its users.
 164  */
 165 struct preempt_ops {
 166         void (*sched_in)(struct preempt_notifier *notifier, int cpu);
 167         void (*sched_out)(struct preempt_notifier *notifier,
 168                           struct task_struct *next);
 169 };
 170
 171 /**
 172  * preempt_notifier - key for installing preemption notifiers
 173  * @link: internal use
 174  * @ops: defines the notifier functions to be called
 175  *
 176  * Usually used in conjunction with container_of().
 177  */
 178 struct preempt_notifier {
 179         struct hlist_node link;
 180         struct preempt_ops *ops;
 181 };
 182
 183 void preempt_notifier_register(struct preempt_notifier *notifier);
 184 void preempt_notifier_unregister(struct preempt_notifier *notifier);
 185
 186 static inline void preempt_notifier_init(struct preempt_notifier *notifier,
 187                                      struct preempt_ops *ops)
 188 {
 189         INIT_HLIST_NODE(&notifier->link);
 190         notifier->ops = ops;
 191 }
 192
 193 #endif
 194
 195 #endif /* __LINUX_PREEMPT_H */