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 <linux/thread_info.h> 8 9 DECLARE_PER_CPU(int, __preempt_count); 10 11 /* 12 * We use the PREEMPT_NEED_RESCHED bit as an inverted NEED_RESCHED such 13 * that a decrement hitting 0 means we can and should reschedule. 14 */ 15 #define PREEMPT_ENABLED (0 + PREEMPT_NEED_RESCHED) 16 17 /* 18 * We mask the PREEMPT_NEED_RESCHED bit so as not to confuse all current users 19 * that think a non-zero value indicates we cannot preempt. 20 */ 21 static __always_inline int preempt_count(void) 22 { 23 return raw_cpu_read_4(__preempt_count) & ~PREEMPT_NEED_RESCHED; 24 } 25 26 static __always_inline void preempt_count_set(int pc) 27 { 28 int old, new; 29 30 do { 31 old = raw_cpu_read_4(__preempt_count); 32 new = (old & PREEMPT_NEED_RESCHED) | 33 (pc & ~PREEMPT_NEED_RESCHED); 34 } while (raw_cpu_cmpxchg_4(__preempt_count, old, new) != old); 35 } 36 37 /* 38 * must be macros to avoid header recursion hell 39 */ 40 #define init_task_preempt_count(p) do { } while (0) 41 42 #define init_idle_preempt_count(p, cpu) do { \ 43 per_cpu(__preempt_count, (cpu)) = PREEMPT_ENABLED; \ 44 } while (0) 45 46 /* 47 * We fold the NEED_RESCHED bit into the preempt count such that 48 * preempt_enable() can decrement and test for needing to reschedule with a 49 * single instruction. 50 * 51 * We invert the actual bit, so that when the decrement hits 0 we know we both 52 * need to resched (the bit is cleared) and can resched (no preempt count). 53 */ 54 55 static __always_inline void set_preempt_need_resched(void) 56 { 57 raw_cpu_and_4(__preempt_count, ~PREEMPT_NEED_RESCHED); 58 } 59 60 static __always_inline void clear_preempt_need_resched(void) 61 { 62 raw_cpu_or_4(__preempt_count, PREEMPT_NEED_RESCHED); 63 } 64 65 static __always_inline bool test_preempt_need_resched(void) 66 { 67 return !(raw_cpu_read_4(__preempt_count) & PREEMPT_NEED_RESCHED); 68 } 69 70 /* 71 * The various preempt_count add/sub methods 72 */ 73 74 static __always_inline void __preempt_count_add(int val) 75 { 76 raw_cpu_add_4(__preempt_count, val); 77 } 78 79 static __always_inline void __preempt_count_sub(int val) 80 { 81 raw_cpu_add_4(__preempt_count, -val); 82 } 83 84 /* 85 * Because we keep PREEMPT_NEED_RESCHED set when we do _not_ need to reschedule 86 * a decrement which hits zero means we have no preempt_count and should 87 * reschedule. 88 */ 89 static __always_inline bool __preempt_count_dec_and_test(void) 90 { 91 return GEN_UNARY_RMWcc("decl", __preempt_count, e, __percpu_arg([var])); 92 } 93 94 /* 95 * Returns true when we need to resched and can (barring IRQ state). 96 */ 97 static __always_inline bool should_resched(int preempt_offset) 98 { 99 return unlikely(raw_cpu_read_4(__preempt_count) == preempt_offset); 100 } 101 102 #ifdef CONFIG_PREEMPT 103 extern asmlinkage void ___preempt_schedule(void); 104 # define __preempt_schedule() \ 105 asm volatile ("call ___preempt_schedule" : ASM_CALL_CONSTRAINT) 106 107 extern asmlinkage void preempt_schedule(void); 108 extern asmlinkage void ___preempt_schedule_notrace(void); 109 # define __preempt_schedule_notrace() \ 110 asm volatile ("call ___preempt_schedule_notrace" : ASM_CALL_CONSTRAINT) 111 112 extern asmlinkage void preempt_schedule_notrace(void); 113 #endif 114 115 #endif /* __ASM_PREEMPT_H */ 116