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 raw_cpu_write_4(__preempt_count, pc); 28 } 29 30 /* 31 * must be macros to avoid header recursion hell 32 */ 33 #define init_task_preempt_count(p) do { } while (0) 34 35 #define init_idle_preempt_count(p, cpu) do { \ 36 per_cpu(__preempt_count, (cpu)) = PREEMPT_ENABLED; \ 37 } while (0) 38 39 /* 40 * We fold the NEED_RESCHED bit into the preempt count such that 41 * preempt_enable() can decrement and test for needing to reschedule with a 42 * single instruction. 43 * 44 * We invert the actual bit, so that when the decrement hits 0 we know we both 45 * need to resched (the bit is cleared) and can resched (no preempt count). 46 */ 47 48 static __always_inline void set_preempt_need_resched(void) 49 { 50 raw_cpu_and_4(__preempt_count, ~PREEMPT_NEED_RESCHED); 51 } 52 53 static __always_inline void clear_preempt_need_resched(void) 54 { 55 raw_cpu_or_4(__preempt_count, PREEMPT_NEED_RESCHED); 56 } 57 58 static __always_inline bool test_preempt_need_resched(void) 59 { 60 return !(raw_cpu_read_4(__preempt_count) & PREEMPT_NEED_RESCHED); 61 } 62 63 /* 64 * The various preempt_count add/sub methods 65 */ 66 67 static __always_inline void __preempt_count_add(int val) 68 { 69 raw_cpu_add_4(__preempt_count, val); 70 } 71 72 static __always_inline void __preempt_count_sub(int val) 73 { 74 raw_cpu_add_4(__preempt_count, -val); 75 } 76 77 /* 78 * Because we keep PREEMPT_NEED_RESCHED set when we do _not_ need to reschedule 79 * a decrement which hits zero means we have no preempt_count and should 80 * reschedule. 81 */ 82 static __always_inline bool __preempt_count_dec_and_test(void) 83 { 84 GEN_UNARY_RMWcc("decl", __preempt_count, __percpu_arg(0), e); 85 } 86 87 /* 88 * Returns true when we need to resched and can (barring IRQ state). 89 */ 90 static __always_inline bool should_resched(int preempt_offset) 91 { 92 return unlikely(raw_cpu_read_4(__preempt_count) == preempt_offset); 93 } 94 95 #ifdef CONFIG_PREEMPT 96 extern asmlinkage void ___preempt_schedule(void); 97 # define __preempt_schedule() \ 98 ({ \ 99 register void *__sp asm(_ASM_SP); \ 100 asm volatile ("call ___preempt_schedule" : "+r"(__sp)); \ 101 }) 102 103 extern asmlinkage void preempt_schedule(void); 104 extern asmlinkage void ___preempt_schedule_notrace(void); 105 # define __preempt_schedule_notrace() \ 106 ({ \ 107 register void *__sp asm(_ASM_SP); \ 108 asm volatile ("call ___preempt_schedule_notrace" : "+r"(__sp)); \ 109 }) 110 extern asmlinkage void preempt_schedule_notrace(void); 111 #endif 112 113 #endif /* __ASM_PREEMPT_H */ 114