1 #ifndef __LINUX_PREEMPT_H 2 #define __LINUX_PREEMPT_H 3 4 /* 5 * include/linux/preempt.h - macros for accessing and manipulating 6 * preempt_count (used for kernel preemption, interrupt count, etc.) 7 */ 8 9 #include <linux/linkage.h> 10 #include <linux/list.h> 11 12 /* 13 * We use the MSB mostly because its available; see <linux/preempt_mask.h> for 14 * the other bits -- can't include that header due to inclusion hell. 15 */ 16 #define PREEMPT_NEED_RESCHED 0x80000000 17 18 #include <asm/preempt.h> 19 20 #if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_PREEMPT_TRACER) 21 extern void preempt_count_add(int val); 22 extern void preempt_count_sub(int val); 23 #define preempt_count_dec_and_test() ({ preempt_count_sub(1); should_resched(); }) 24 #else 25 #define preempt_count_add(val) __preempt_count_add(val) 26 #define preempt_count_sub(val) __preempt_count_sub(val) 27 #define preempt_count_dec_and_test() __preempt_count_dec_and_test() 28 #endif 29 30 #define __preempt_count_inc() __preempt_count_add(1) 31 #define __preempt_count_dec() __preempt_count_sub(1) 32 33 #define preempt_count_inc() preempt_count_add(1) 34 #define preempt_count_dec() preempt_count_sub(1) 35 36 #ifdef CONFIG_PREEMPT_COUNT 37 38 #define preempt_disable() \ 39 do { \ 40 preempt_count_inc(); \ 41 barrier(); \ 42 } while (0) 43 44 #define sched_preempt_enable_no_resched() \ 45 do { \ 46 barrier(); \ 47 preempt_count_dec(); \ 48 } while (0) 49 50 #define preempt_enable_no_resched() sched_preempt_enable_no_resched() 51 52 #ifdef CONFIG_PREEMPT 53 #define preempt_enable() \ 54 do { \ 55 barrier(); \ 56 if (unlikely(preempt_count_dec_and_test())) \ 57 __preempt_schedule(); \ 58 } while (0) 59 60 #define preempt_check_resched() \ 61 do { \ 62 if (should_resched()) \ 63 __preempt_schedule(); \ 64 } while (0) 65 66 #else 67 #define preempt_enable() preempt_enable_no_resched() 68 #define preempt_check_resched() do { } while (0) 69 #endif 70 71 #define preempt_disable_notrace() \ 72 do { \ 73 __preempt_count_inc(); \ 74 barrier(); \ 75 } while (0) 76 77 #define preempt_enable_no_resched_notrace() \ 78 do { \ 79 barrier(); \ 80 __preempt_count_dec(); \ 81 } while (0) 82 83 #ifdef CONFIG_PREEMPT 84 85 #ifndef CONFIG_CONTEXT_TRACKING 86 #define __preempt_schedule_context() __preempt_schedule() 87 #endif 88 89 #define preempt_enable_notrace() \ 90 do { \ 91 barrier(); \ 92 if (unlikely(__preempt_count_dec_and_test())) \ 93 __preempt_schedule_context(); \ 94 } while (0) 95 #else 96 #define preempt_enable_notrace() preempt_enable_no_resched_notrace() 97 #endif 98 99 #else /* !CONFIG_PREEMPT_COUNT */ 100 101 /* 102 * Even if we don't have any preemption, we need preempt disable/enable 103 * to be barriers, so that we don't have things like get_user/put_user 104 * that can cause faults and scheduling migrate into our preempt-protected 105 * region. 106 */ 107 #define preempt_disable() barrier() 108 #define sched_preempt_enable_no_resched() barrier() 109 #define preempt_enable_no_resched() barrier() 110 #define preempt_enable() barrier() 111 #define preempt_check_resched() do { } while (0) 112 113 #define preempt_disable_notrace() barrier() 114 #define preempt_enable_no_resched_notrace() barrier() 115 #define preempt_enable_notrace() barrier() 116 117 #endif /* CONFIG_PREEMPT_COUNT */ 118 119 #ifdef CONFIG_PREEMPT_NOTIFIERS 120 121 struct preempt_notifier; 122 123 /** 124 * preempt_ops - notifiers called when a task is preempted and rescheduled 125 * @sched_in: we're about to be rescheduled: 126 * notifier: struct preempt_notifier for the task being scheduled 127 * cpu: cpu we're scheduled on 128 * @sched_out: we've just been preempted 129 * notifier: struct preempt_notifier for the task being preempted 130 * next: the task that's kicking us out 131 * 132 * Please note that sched_in and out are called under different 133 * contexts. sched_out is called with rq lock held and irq disabled 134 * while sched_in is called without rq lock and irq enabled. This 135 * difference is intentional and depended upon by its users. 136 */ 137 struct preempt_ops { 138 void (*sched_in)(struct preempt_notifier *notifier, int cpu); 139 void (*sched_out)(struct preempt_notifier *notifier, 140 struct task_struct *next); 141 }; 142 143 /** 144 * preempt_notifier - key for installing preemption notifiers 145 * @link: internal use 146 * @ops: defines the notifier functions to be called 147 * 148 * Usually used in conjunction with container_of(). 149 */ 150 struct preempt_notifier { 151 struct hlist_node link; 152 struct preempt_ops *ops; 153 }; 154 155 void preempt_notifier_register(struct preempt_notifier *notifier); 156 void preempt_notifier_unregister(struct preempt_notifier *notifier); 157 158 static inline void preempt_notifier_init(struct preempt_notifier *notifier, 159 struct preempt_ops *ops) 160 { 161 INIT_HLIST_NODE(¬ifier->link); 162 notifier->ops = ops; 163 } 164 165 #endif 166 167 #endif /* __LINUX_PREEMPT_H */ 168