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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 { \
  34.         task_thread_info(p)->saved_preempt_count = PREEMPT_DISABLED; \
  35. } while (0)
  36.  
  37. #define init_idle_preempt_count(p, cpu) do { \
  38.         task_thread_info(p)->saved_preempt_count = PREEMPT_ENABLED; \
  39.         per_cpu(__preempt_count, (cpu)) = PREEMPT_ENABLED; \
  40. } while (0)
  41.  
  42. /*
  43.  * We fold the NEED_RESCHED bit into the preempt count such that
  44.  * preempt_enable() can decrement and test for needing to reschedule with a
  45.  * single instruction.
  46.  *
  47.  * We invert the actual bit, so that when the decrement hits 0 we know we both
  48.  * need to resched (the bit is cleared) and can resched (no preempt count).
  49.  */
  50.  
  51. static __always_inline void set_preempt_need_resched(void)
  52. {
  53.         raw_cpu_and_4(__preempt_count, ~PREEMPT_NEED_RESCHED);
  54. }
  55.  
  56. static __always_inline void clear_preempt_need_resched(void)
  57. {
  58.         raw_cpu_or_4(__preempt_count, PREEMPT_NEED_RESCHED);
  59. }
  60.  
  61. static __always_inline bool test_preempt_need_resched(void)
  62. {
  63.         return !(raw_cpu_read_4(__preempt_count) & PREEMPT_NEED_RESCHED);
  64. }
  65.  
  66. /*
  67.  * The various preempt_count add/sub methods
  68.  */
  69.  
  70. static __always_inline void __preempt_count_add(int val)
  71. {
  72.         raw_cpu_add_4(__preempt_count, val);
  73. }
  74.  
  75. static __always_inline void __preempt_count_sub(int val)
  76. {
  77.         raw_cpu_add_4(__preempt_count, -val);
  78. }
  79.  
  80. /*
  81.  * Because we keep PREEMPT_NEED_RESCHED set when we do _not_ need to reschedule
  82.  * a decrement which hits zero means we have no preempt_count and should
  83.  * reschedule.
  84.  */
  85. static __always_inline bool __preempt_count_dec_and_test(void)
  86. {
  87.         GEN_UNARY_RMWcc("decl", __preempt_count, __percpu_arg(0), "e");
  88. }
  89.  
  90. /*
  91.  * Returns true when we need to resched and can (barring IRQ state).
  92.  */
  93. static __always_inline bool should_resched(void)
  94. {
  95.         return unlikely(!raw_cpu_read_4(__preempt_count));
  96. }
  97.  
  98. #ifdef CONFIG_PREEMPT
  99.   extern asmlinkage void ___preempt_schedule(void);
  100. # define __preempt_schedule() asm ("call ___preempt_schedule")
  101.   extern asmlinkage void preempt_schedule(void);
  102. # ifdef CONFIG_CONTEXT_TRACKING
  103.     extern asmlinkage void ___preempt_schedule_context(void);
  104. #   define __preempt_schedule_context() asm ("call ___preempt_schedule_context")
  105.     extern asmlinkage void preempt_schedule_context(void);
  106. # endif
  107. #endif
  108.  
  109. #endif /* __ASM_PREEMPT_H */
  110.