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