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/static_call_types.h> 10 11/* We use the MSB mostly because its available */ 12#define PREEMPT_NEED_RESCHED 0x80000000 13 14/* 15 * We use the PREEMPT_NEED_RESCHED bit as an inverted NEED_RESCHED such 16 * that a decrement hitting 0 means we can and should reschedule. 17 */ 18#define PREEMPT_ENABLED (0 + PREEMPT_NEED_RESCHED) 19 20/* 21 * We mask the PREEMPT_NEED_RESCHED bit so as not to confuse all current users 22 * that think a non-zero value indicates we cannot preempt. 23 */ 24static __always_inline int preempt_count(void) 25{ 26 return raw_cpu_read_4(pcpu_hot.preempt_count) & ~PREEMPT_NEED_RESCHED; 27} 28 29static __always_inline void preempt_count_set(int pc) 30{ 31 int old, new; 32 33 old = raw_cpu_read_4(pcpu_hot.preempt_count); 34 do { 35 new = (old & PREEMPT_NEED_RESCHED) | 36 (pc & ~PREEMPT_NEED_RESCHED); 37 } while (!raw_cpu_try_cmpxchg_4(pcpu_hot.preempt_count, &old, new)); 38} 39 40/* 41 * must be macros to avoid header recursion hell 42 */ 43#define init_task_preempt_count(p) do { } while (0) 44 45#define init_idle_preempt_count(p, cpu) do { \ 46 per_cpu(pcpu_hot.preempt_count, (cpu)) = PREEMPT_DISABLED; \ 47} while (0) 48 49/* 50 * We fold the NEED_RESCHED bit into the preempt count such that 51 * preempt_enable() can decrement and test for needing to reschedule with a 52 * single instruction. 53 * 54 * We invert the actual bit, so that when the decrement hits 0 we know we both 55 * need to resched (the bit is cleared) and can resched (no preempt count). 56 */ 57 58static __always_inline void set_preempt_need_resched(void) 59{ 60 raw_cpu_and_4(pcpu_hot.preempt_count, ~PREEMPT_NEED_RESCHED); 61} 62 63static __always_inline void clear_preempt_need_resched(void) 64{ 65 raw_cpu_or_4(pcpu_hot.preempt_count, PREEMPT_NEED_RESCHED); 66} 67 68static __always_inline bool test_preempt_need_resched(void) 69{ 70 return !(raw_cpu_read_4(pcpu_hot.preempt_count) & PREEMPT_NEED_RESCHED); 71} 72 73/* 74 * The various preempt_count add/sub methods 75 */ 76 77static __always_inline void __preempt_count_add(int val) 78{ 79 raw_cpu_add_4(pcpu_hot.preempt_count, val); 80} 81 82static __always_inline void __preempt_count_sub(int val) 83{ 84 raw_cpu_add_4(pcpu_hot.preempt_count, -val); 85} 86 87/* 88 * Because we keep PREEMPT_NEED_RESCHED set when we do _not_ need to reschedule 89 * a decrement which hits zero means we have no preempt_count and should 90 * reschedule. 91 */ 92static __always_inline bool __preempt_count_dec_and_test(void) 93{ 94 return GEN_UNARY_RMWcc("decl", __my_cpu_var(pcpu_hot.preempt_count), e, 95 __percpu_arg([var])); 96} 97 98/* 99 * Returns true when we need to resched and can (barring IRQ state). 100 */ 101static __always_inline bool should_resched(int preempt_offset) 102{ 103 return unlikely(raw_cpu_read_4(pcpu_hot.preempt_count) == preempt_offset); 104} 105 106#ifdef CONFIG_PREEMPTION 107 108extern asmlinkage void preempt_schedule(void); 109extern asmlinkage void preempt_schedule_thunk(void); 110 111#define preempt_schedule_dynamic_enabled preempt_schedule_thunk 112#define preempt_schedule_dynamic_disabled NULL 113 114extern asmlinkage void preempt_schedule_notrace(void); 115extern asmlinkage void preempt_schedule_notrace_thunk(void); 116 117#define preempt_schedule_notrace_dynamic_enabled preempt_schedule_notrace_thunk 118#define preempt_schedule_notrace_dynamic_disabled NULL 119 120#ifdef CONFIG_PREEMPT_DYNAMIC 121 122DECLARE_STATIC_CALL(preempt_schedule, preempt_schedule_dynamic_enabled); 123 124#define __preempt_schedule() \ 125do { \ 126 __STATIC_CALL_MOD_ADDRESSABLE(preempt_schedule); \ 127 asm volatile ("call " STATIC_CALL_TRAMP_STR(preempt_schedule) : ASM_CALL_CONSTRAINT); \ 128} while (0) 129 130DECLARE_STATIC_CALL(preempt_schedule_notrace, preempt_schedule_notrace_dynamic_enabled); 131 132#define __preempt_schedule_notrace() \ 133do { \ 134 __STATIC_CALL_MOD_ADDRESSABLE(preempt_schedule_notrace); \ 135 asm volatile ("call " STATIC_CALL_TRAMP_STR(preempt_schedule_notrace) : ASM_CALL_CONSTRAINT); \ 136} while (0) 137 138#else /* PREEMPT_DYNAMIC */ 139 140#define __preempt_schedule() \ 141 asm volatile ("call preempt_schedule_thunk" : ASM_CALL_CONSTRAINT); 142 143#define __preempt_schedule_notrace() \ 144 asm volatile ("call preempt_schedule_notrace_thunk" : ASM_CALL_CONSTRAINT); 145 146#endif /* PREEMPT_DYNAMIC */ 147 148#endif /* PREEMPTION */ 149 150#endif /* __ASM_PREEMPT_H */ 151