1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef __ASM_PREEMPT_H 3 #define __ASM_PREEMPT_H 4 5 #include <asm/rmwcc.h> 6 #include <asm/percpu.h> 7 #include <asm/current.h> 8 9 #include <linux/thread_info.h> 10 #include <linux/static_call_types.h> 11 12 /* We use the MSB mostly because its available */ 13 #define PREEMPT_NEED_RESCHED 0x80000000 14 15 /* 16 * We use the PREEMPT_NEED_RESCHED bit as an inverted NEED_RESCHED such 17 * that a decrement hitting 0 means we can and should reschedule. 18 */ 19 #define PREEMPT_ENABLED (0 + PREEMPT_NEED_RESCHED) 20 21 /* 22 * We mask the PREEMPT_NEED_RESCHED bit so as not to confuse all current users 23 * that think a non-zero value indicates we cannot preempt. 24 */ 25 static __always_inline int preempt_count(void) 26 { 27 return raw_cpu_read_4(pcpu_hot.preempt_count) & ~PREEMPT_NEED_RESCHED; 28 } 29 30 static __always_inline void preempt_count_set(int pc) 31 { 32 int old, new; 33 34 do { 35 old = raw_cpu_read_4(pcpu_hot.preempt_count); 36 new = (old & PREEMPT_NEED_RESCHED) | 37 (pc & ~PREEMPT_NEED_RESCHED); 38 } while (raw_cpu_cmpxchg_4(pcpu_hot.preempt_count, old, new) != old); 39 } 40 41 /* 42 * must be macros to avoid header recursion hell 43 */ 44 #define init_task_preempt_count(p) do { } while (0) 45 46 #define init_idle_preempt_count(p, cpu) do { \ 47 per_cpu(pcpu_hot.preempt_count, (cpu)) = PREEMPT_DISABLED; \ 48 } while (0) 49 50 /* 51 * We fold the NEED_RESCHED bit into the preempt count such that 52 * preempt_enable() can decrement and test for needing to reschedule with a 53 * single instruction. 54 * 55 * We invert the actual bit, so that when the decrement hits 0 we know we both 56 * need to resched (the bit is cleared) and can resched (no preempt count). 57 */ 58 59 static __always_inline void set_preempt_need_resched(void) 60 { 61 raw_cpu_and_4(pcpu_hot.preempt_count, ~PREEMPT_NEED_RESCHED); 62 } 63 64 static __always_inline void clear_preempt_need_resched(void) 65 { 66 raw_cpu_or_4(pcpu_hot.preempt_count, PREEMPT_NEED_RESCHED); 67 } 68 69 static __always_inline bool test_preempt_need_resched(void) 70 { 71 return !(raw_cpu_read_4(pcpu_hot.preempt_count) & PREEMPT_NEED_RESCHED); 72 } 73 74 /* 75 * The various preempt_count add/sub methods 76 */ 77 78 static __always_inline void __preempt_count_add(int val) 79 { 80 raw_cpu_add_4(pcpu_hot.preempt_count, val); 81 } 82 83 static __always_inline void __preempt_count_sub(int val) 84 { 85 raw_cpu_add_4(pcpu_hot.preempt_count, -val); 86 } 87 88 /* 89 * Because we keep PREEMPT_NEED_RESCHED set when we do _not_ need to reschedule 90 * a decrement which hits zero means we have no preempt_count and should 91 * reschedule. 92 */ 93 static __always_inline bool __preempt_count_dec_and_test(void) 94 { 95 return GEN_UNARY_RMWcc("decl", pcpu_hot.preempt_count, e, 96 __percpu_arg([var])); 97 } 98 99 /* 100 * Returns true when we need to resched and can (barring IRQ state). 101 */ 102 static __always_inline bool should_resched(int preempt_offset) 103 { 104 return unlikely(raw_cpu_read_4(pcpu_hot.preempt_count) == preempt_offset); 105 } 106 107 #ifdef CONFIG_PREEMPTION 108 109 extern asmlinkage void preempt_schedule(void); 110 extern asmlinkage void preempt_schedule_thunk(void); 111 112 #define preempt_schedule_dynamic_enabled preempt_schedule_thunk 113 #define preempt_schedule_dynamic_disabled NULL 114 115 extern asmlinkage void preempt_schedule_notrace(void); 116 extern asmlinkage void preempt_schedule_notrace_thunk(void); 117 118 #define preempt_schedule_notrace_dynamic_enabled preempt_schedule_notrace_thunk 119 #define preempt_schedule_notrace_dynamic_disabled NULL 120 121 #ifdef CONFIG_PREEMPT_DYNAMIC 122 123 DECLARE_STATIC_CALL(preempt_schedule, preempt_schedule_dynamic_enabled); 124 125 #define __preempt_schedule() \ 126 do { \ 127 __STATIC_CALL_MOD_ADDRESSABLE(preempt_schedule); \ 128 asm volatile ("call " STATIC_CALL_TRAMP_STR(preempt_schedule) : ASM_CALL_CONSTRAINT); \ 129 } while (0) 130 131 DECLARE_STATIC_CALL(preempt_schedule_notrace, preempt_schedule_notrace_dynamic_enabled); 132 133 #define __preempt_schedule_notrace() \ 134 do { \ 135 __STATIC_CALL_MOD_ADDRESSABLE(preempt_schedule_notrace); \ 136 asm volatile ("call " STATIC_CALL_TRAMP_STR(preempt_schedule_notrace) : ASM_CALL_CONSTRAINT); \ 137 } while (0) 138 139 #else /* PREEMPT_DYNAMIC */ 140 141 #define __preempt_schedule() \ 142 asm volatile ("call preempt_schedule_thunk" : ASM_CALL_CONSTRAINT); 143 144 #define __preempt_schedule_notrace() \ 145 asm volatile ("call preempt_schedule_notrace_thunk" : ASM_CALL_CONSTRAINT); 146 147 #endif /* PREEMPT_DYNAMIC */ 148 149 #endif /* PREEMPTION */ 150 151 #endif /* __ASM_PREEMPT_H */ 152