include/asm/preempt.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef __ASM_PREEMPT_H
   3 #define __ASM_PREEMPT_H
   4
   5 #include <asm/current.h>
   6 #include <linux/thread_info.h>
   7 #include <asm/atomic_ops.h>
   8
   9 #ifdef CONFIG_HAVE_MARCH_Z196_FEATURES
  10
  11 /* We use the MSB mostly because its available */
  12 #define PREEMPT_NEED_RESCHED    0x80000000
  13 #define PREEMPT_ENABLED (0 + PREEMPT_NEED_RESCHED)
  14
  15 static inline int preempt_count(void)
  16 {
  17         return READ_ONCE(S390_lowcore.preempt_count) & ~PREEMPT_NEED_RESCHED;
  18 }
  19
  20 static inline void preempt_count_set(int pc)
  21 {
  22         int old, new;
  23
  24         do {
  25                 old = READ_ONCE(S390_lowcore.preempt_count);
  26                 new = (old & PREEMPT_NEED_RESCHED) |
  27                         (pc & ~PREEMPT_NEED_RESCHED);
  28         } while (__atomic_cmpxchg(&S390_lowcore.preempt_count,
  29                                   old, new) != old);
  30 }
  31
  32 #define init_task_preempt_count(p)      do { } while (0)
  33
  34 #define init_idle_preempt_count(p, cpu) do { \
  35         S390_lowcore.preempt_count = PREEMPT_ENABLED; \
  36 } while (0)
  37
  38 static inline void set_preempt_need_resched(void)
  39 {
  40         __atomic_and(~PREEMPT_NEED_RESCHED, &S390_lowcore.preempt_count);
  41 }
  42
  43 static inline void clear_preempt_need_resched(void)
  44 {
  45         __atomic_or(PREEMPT_NEED_RESCHED, &S390_lowcore.preempt_count);
  46 }
  47
  48 static inline bool test_preempt_need_resched(void)
  49 {
  50         return !(READ_ONCE(S390_lowcore.preempt_count) & PREEMPT_NEED_RESCHED);
  51 }
  52
  53 static inline void __preempt_count_add(int val)
  54 {
  55         /*
  56          * With some obscure config options and CONFIG_PROFILE_ALL_BRANCHES
  57          * enabled, gcc 12 fails to handle __builtin_constant_p().
  58          */
  59         if (!IS_ENABLED(CONFIG_PROFILE_ALL_BRANCHES)) {
  60                 if (__builtin_constant_p(val) && (val >= -128) && (val <= 127)) {
  61                         __atomic_add_const(val, &S390_lowcore.preempt_count);
  62                         return;
  63                 }
  64         }
  65         __atomic_add(val, &S390_lowcore.preempt_count);
  66 }
  67
  68 static inline void __preempt_count_sub(int val)
  69 {
  70         __preempt_count_add(-val);
  71 }
  72
  73 static inline bool __preempt_count_dec_and_test(void)
  74 {
  75         return __atomic_add(-1, &S390_lowcore.preempt_count) == 1;
  76 }
  77
  78 static inline bool should_resched(int preempt_offset)
  79 {
  80         return unlikely(READ_ONCE(S390_lowcore.preempt_count) ==
  81                         preempt_offset);
  82 }
  83
  84 #else /* CONFIG_HAVE_MARCH_Z196_FEATURES */
  85
  86 #define PREEMPT_ENABLED (0)
  87
  88 static inline int preempt_count(void)
  89 {
  90         return READ_ONCE(S390_lowcore.preempt_count);
  91 }
  92
  93 static inline void preempt_count_set(int pc)
  94 {
  95         S390_lowcore.preempt_count = pc;
  96 }
  97
  98 #define init_task_preempt_count(p)      do { } while (0)
  99
 100 #define init_idle_preempt_count(p, cpu) do { \
 101         S390_lowcore.preempt_count = PREEMPT_ENABLED; \
 102 } while (0)
 103
 104 static inline void set_preempt_need_resched(void)
 105 {
 106 }
 107
 108 static inline void clear_preempt_need_resched(void)
 109 {
 110 }
 111
 112 static inline bool test_preempt_need_resched(void)
 113 {
 114         return false;
 115 }
 116
 117 static inline void __preempt_count_add(int val)
 118 {
 119         S390_lowcore.preempt_count += val;
 120 }
 121
 122 static inline void __preempt_count_sub(int val)
 123 {
 124         S390_lowcore.preempt_count -= val;
 125 }
 126
 127 static inline bool __preempt_count_dec_and_test(void)
 128 {
 129         return !--S390_lowcore.preempt_count && tif_need_resched();
 130 }
 131
 132 static inline bool should_resched(int preempt_offset)
 133 {
 134         return unlikely(preempt_count() == preempt_offset &&
 135                         tif_need_resched());
 136 }
 137
 138 #endif /* CONFIG_HAVE_MARCH_Z196_FEATURES */
 139
 140 #ifdef CONFIG_PREEMPT
 141 extern asmlinkage void preempt_schedule(void);
 142 #define __preempt_schedule() preempt_schedule()
 143 extern asmlinkage void preempt_schedule_notrace(void);
 144 #define __preempt_schedule_notrace() preempt_schedule_notrace()
 145 #endif /* CONFIG_PREEMPT */
 146
 147 #endif /* __ASM_PREEMPT_H */