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 int old, new; 28 29 do { 30 old = raw_cpu_read_4(__preempt_count); 31 new = (old & PREEMPT_NEED_RESCHED) | 32 (pc & ~PREEMPT_NEED_RESCHED); 33 } while (raw_cpu_cmpxchg_4(__preempt_count, old, new) != old); 34 } 35 36 /* 37 * must be macros to avoid header recursion hell 38 */ 39 #define init_task_preempt_count(p) do { } while (0) 40 41 #define init_idle_preempt_count(p, cpu) do { \ 42 per_cpu(__preempt_count, (cpu)) = PREEMPT_ENABLED; \ 43 } while (0) 44 45 /* 46 * We fold the NEED_RESCHED bit into the preempt count such that 47 * preempt_enable() can decrement and test for needing to reschedule with a 48 * single instruction. 49 * 50 * We invert the actual bit, so that when the decrement hits 0 we know we both 51 * need to resched (the bit is cleared) and can resched (no preempt count). 52 */ 53 54 static __always_inline void set_preempt_need_resched(void) 55 { 56 raw_cpu_and_4(__preempt_count, ~PREEMPT_NEED_RESCHED); 57 } 58 59 static __always_inline void clear_preempt_need_resched(void) 60 { 61 raw_cpu_or_4(__preempt_count, PREEMPT_NEED_RESCHED); 62 } 63 64 static __always_inline bool test_preempt_need_resched(void) 65 { 66 return !(raw_cpu_read_4(__preempt_count) & PREEMPT_NEED_RESCHED); 67 } 68 69 /* 70 * The various preempt_count add/sub methods 71 */ 72 73 static __always_inline void __preempt_count_add(int val) 74 { 75 raw_cpu_add_4(__preempt_count, val); 76 } 77 78 static __always_inline void __preempt_count_sub(int val) 79 { 80 raw_cpu_add_4(__preempt_count, -val); 81 } 82 83 /* 84 * Because we keep PREEMPT_NEED_RESCHED set when we do _not_ need to reschedule 85 * a decrement which hits zero means we have no preempt_count and should 86 * reschedule. 87 */ 88 static __always_inline bool __preempt_count_dec_and_test(void) 89 { 90 GEN_UNARY_RMWcc("decl", __preempt_count, __percpu_arg(0), e); 91 } 92 93 /* 94 * Returns true when we need to resched and can (barring IRQ state). 95 */ 96 static __always_inline bool should_resched(int preempt_offset) 97 { 98 return unlikely(raw_cpu_read_4(__preempt_count) == preempt_offset); 99 } 100 101 #ifdef CONFIG_PREEMPT 102 extern asmlinkage void ___preempt_schedule(void); 103 # define __preempt_schedule() \ 104 ({ \ 105 register void *__sp asm(_ASM_SP); \ 106 asm volatile ("call ___preempt_schedule" : "+r"(__sp)); \ 107 }) 108 109 extern asmlinkage void preempt_schedule(void); 110 extern asmlinkage void ___preempt_schedule_notrace(void); 111 # define __preempt_schedule_notrace() \ 112 ({ \ 113 register void *__sp asm(_ASM_SP); \ 114 asm volatile ("call ___preempt_schedule_notrace" : "+r"(__sp)); \ 115 }) 116 extern asmlinkage void preempt_schedule_notrace(void); 117 #endif 118 119 #endif /* __ASM_PREEMPT_H */ 120