include/asm-generic/preempt.h

   1 #ifndef __ASM_PREEMPT_H
   2 #define __ASM_PREEMPT_H
   3
   4 #include <linux/thread_info.h>
   5
   6 #define PREEMPT_ENABLED (0)
   7
   8 static __always_inline int preempt_count(void)
   9 {
  10         return READ_ONCE(current_thread_info()->preempt_count);
  11 }
  12
  13 static __always_inline volatile int *preempt_count_ptr(void)
  14 {
  15         return &current_thread_info()->preempt_count;
  16 }
  17
  18 static __always_inline void preempt_count_set(int pc)
  19 {
  20         *preempt_count_ptr() = pc;
  21 }
  22
  23 /*
  24  * must be macros to avoid header recursion hell
  25  */
  26 #define init_task_preempt_count(p) do { \
  27         task_thread_info(p)->preempt_count = FORK_PREEMPT_COUNT; \
  28 } while (0)
  29
  30 #define init_idle_preempt_count(p, cpu) do { \
  31         task_thread_info(p)->preempt_count = PREEMPT_ENABLED; \
  32 } while (0)
  33
  34 static __always_inline void set_preempt_need_resched(void)
  35 {
  36 }
  37
  38 static __always_inline void clear_preempt_need_resched(void)
  39 {
  40 }
  41
  42 static __always_inline bool test_preempt_need_resched(void)
  43 {
  44         return false;
  45 }
  46
  47 /*
  48  * The various preempt_count add/sub methods
  49  */
  50
  51 static __always_inline void __preempt_count_add(int val)
  52 {
  53         *preempt_count_ptr() += val;
  54 }
  55
  56 static __always_inline void __preempt_count_sub(int val)
  57 {
  58         *preempt_count_ptr() -= val;
  59 }
  60
  61 static __always_inline bool __preempt_count_dec_and_test(void)
  62 {
  63         /*
  64          * Because of load-store architectures cannot do per-cpu atomic
  65          * operations; we cannot use PREEMPT_NEED_RESCHED because it might get
  66          * lost.
  67          */
  68         return !--*preempt_count_ptr() && tif_need_resched();
  69 }
  70
  71 /*
  72  * Returns true when we need to resched and can (barring IRQ state).
  73  */
  74 static __always_inline bool should_resched(int preempt_offset)
  75 {
  76         return unlikely(preempt_count() == preempt_offset &&
  77                         tif_need_resched());
  78 }
  79
  80 #ifdef CONFIG_PREEMPT
  81 extern asmlinkage void preempt_schedule(void);
  82 #define __preempt_schedule() preempt_schedule()
  83 extern asmlinkage void preempt_schedule_notrace(void);
  84 #define __preempt_schedule_notrace() preempt_schedule_notrace()
  85 #endif /* CONFIG_PREEMPT */
  86
  87 #endif /* __ASM_PREEMPT_H */