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 ACCESS_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 task_preempt_count(p) \
  27         (task_thread_info(p)->preempt_count & ~PREEMPT_NEED_RESCHED)
  28
  29 #define init_task_preempt_count(p) do { \
  30         task_thread_info(p)->preempt_count = PREEMPT_DISABLED; \
  31 } while (0)
  32
  33 #define init_idle_preempt_count(p, cpu) do { \
  34         task_thread_info(p)->preempt_count = PREEMPT_ENABLED; \
  35 } while (0)
  36
  37 static __always_inline void set_preempt_need_resched(void)
  38 {
  39 }
  40
  41 static __always_inline void clear_preempt_need_resched(void)
  42 {
  43 }
  44
  45 static __always_inline bool test_preempt_need_resched(void)
  46 {
  47         return false;
  48 }
  49
  50 /*
  51  * The various preempt_count add/sub methods
  52  */
  53
  54 static __always_inline void __preempt_count_add(int val)
  55 {
  56         *preempt_count_ptr() += val;
  57 }
  58
  59 static __always_inline void __preempt_count_sub(int val)
  60 {
  61         *preempt_count_ptr() -= val;
  62 }
  63
  64 static __always_inline bool __preempt_count_dec_and_test(void)
  65 {
  66         /*
  67          * Because of load-store architectures cannot do per-cpu atomic
  68          * operations; we cannot use PREEMPT_NEED_RESCHED because it might get
  69          * lost.
  70          */
  71         return !--*preempt_count_ptr() && tif_need_resched();
  72 }
  73
  74 /*
  75  * Returns true when we need to resched and can (barring IRQ state).
  76  */
  77 static __always_inline bool should_resched(int preempt_offset)
  78 {
  79         return unlikely(preempt_count() == preempt_offset &&
  80                         tif_need_resched());
  81 }
  82
  83 #ifdef CONFIG_PREEMPT
  84 extern asmlinkage void preempt_schedule(void);
  85 #define __preempt_schedule() preempt_schedule()
  86
  87 #ifdef CONFIG_CONTEXT_TRACKING
  88 extern asmlinkage void preempt_schedule_context(void);
  89 #define __preempt_schedule_context() preempt_schedule_context()
  90 #endif
  91 #endif /* CONFIG_PREEMPT */
  92
  93 #endif /* __ASM_PREEMPT_H */