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  1. #ifndef __ASM_PREEMPT_H
  2. #define __ASM_PREEMPT_H
  3.  
  4. #include <asm/rmwcc.h>
  5. #include <asm/percpu.h>
  6. //#include <linux/thread_info.h>
  7.  
  8. DECLARE_PER_CPU(int, __preempt_count);
  9.  
  10. /*
  11.  * We use the PREEMPT_NEED_RESCHED bit as an inverted NEED_RESCHED such
  12.  * that a decrement hitting 0 means we can and should reschedule.
  13.  */
  14. #define PREEMPT_ENABLED (0 + PREEMPT_NEED_RESCHED)
  15.  
  16. /*
  17.  * We mask the PREEMPT_NEED_RESCHED bit so as not to confuse all current users
  18.  * that think a non-zero value indicates we cannot preempt.
  19.  */
  20. static __always_inline int preempt_count(void)
  21. {
  22.         return raw_cpu_read_4(__preempt_count) & ~PREEMPT_NEED_RESCHED;
  23. }
  24.  
  25. static __always_inline void preempt_count_set(int pc)
  26. {
  27.         raw_cpu_write_4(__preempt_count, pc);
  28. }
  29.  
  30. /*
  31.  * must be macros to avoid header recursion hell
  32.  */
  33. #define init_task_preempt_count(p) do { } while (0)
  34.  
  35. #define init_idle_preempt_count(p, cpu) do { \
  36.         per_cpu(__preempt_count, (cpu)) = PREEMPT_ENABLED; \
  37. } while (0)
  38.  
  39. /*
  40.  * We fold the NEED_RESCHED bit into the preempt count such that
  41.  * preempt_enable() can decrement and test for needing to reschedule with a
  42.  * single instruction.
  43.  *
  44.  * We invert the actual bit, so that when the decrement hits 0 we know we both
  45.  * need to resched (the bit is cleared) and can resched (no preempt count).
  46.  */
  47.  
  48. static __always_inline void set_preempt_need_resched(void)
  49. {
  50.         raw_cpu_and_4(__preempt_count, ~PREEMPT_NEED_RESCHED);
  51. }
  52.  
  53. static __always_inline void clear_preempt_need_resched(void)
  54. {
  55.         raw_cpu_or_4(__preempt_count, PREEMPT_NEED_RESCHED);
  56. }
  57.  
  58. static __always_inline bool test_preempt_need_resched(void)
  59. {
  60.         return !(raw_cpu_read_4(__preempt_count) & PREEMPT_NEED_RESCHED);
  61. }
  62.  
  63. /*
  64.  * The various preempt_count add/sub methods
  65.  */
  66.  
  67. static __always_inline void __preempt_count_add(int val)
  68. {
  69.         raw_cpu_add_4(__preempt_count, val);
  70. }
  71.  
  72. static __always_inline void __preempt_count_sub(int val)
  73. {
  74.         raw_cpu_add_4(__preempt_count, -val);
  75. }
  76.  
  77. /*
  78.  * Because we keep PREEMPT_NEED_RESCHED set when we do _not_ need to reschedule
  79.  * a decrement which hits zero means we have no preempt_count and should
  80.  * reschedule.
  81.  */
  82. static __always_inline bool __preempt_count_dec_and_test(void)
  83. {
  84.         GEN_UNARY_RMWcc("decl", __preempt_count, __percpu_arg(0), "e");
  85. }
  86.  
  87. /*
  88.  * Returns true when we need to resched and can (barring IRQ state).
  89.  */
  90. static __always_inline bool should_resched(int preempt_offset)
  91. {
  92.         return unlikely(raw_cpu_read_4(__preempt_count) == preempt_offset);
  93. }
  94.  
  95. #ifdef CONFIG_PREEMPT
  96.   extern asmlinkage void ___preempt_schedule(void);
  97. # define __preempt_schedule() asm ("call ___preempt_schedule")
  98.   extern asmlinkage void preempt_schedule(void);
  99.   extern asmlinkage void ___preempt_schedule_notrace(void);
  100. # define __preempt_schedule_notrace() asm ("call ___preempt_schedule_notrace")
  101.   extern asmlinkage void preempt_schedule_notrace(void);
  102. #endif
  103.  
  104. #endif /* __ASM_PREEMPT_H */
  105.