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() \ 68 do { \ 69 barrier(); \ 70 preempt_count_dec(); \ 71 } while (0) 72 #define preempt_check_resched() do { } while (0) 73 #endif 74 75 #define preempt_disable_notrace() \ 76 do { \ 77 __preempt_count_inc(); \ 78 barrier(); \ 79 } while (0) 80 81 #define preempt_enable_no_resched_notrace() \ 82 do { \ 83 barrier(); \ 84 __preempt_count_dec(); \ 85 } while (0) 86 87 #ifdef CONFIG_PREEMPT 88 89 #ifndef CONFIG_CONTEXT_TRACKING 90 #define __preempt_schedule_context() __preempt_schedule() 91 #endif 92 93 #define preempt_enable_notrace() \ 94 do { \ 95 barrier(); \ 96 if (unlikely(__preempt_count_dec_and_test())) \ 97 __preempt_schedule_context(); \ 98 } while (0) 99 #else 100 #define preempt_enable_notrace() \ 101 do { \ 102 barrier(); \ 103 __preempt_count_dec(); \ 104 } while (0) 105 #endif 106 107 #else /* !CONFIG_PREEMPT_COUNT */ 108 109 /* 110 * Even if we don't have any preemption, we need preempt disable/enable 111 * to be barriers, so that we don't have things like get_user/put_user 112 * that can cause faults and scheduling migrate into our preempt-protected 113 * region. 114 */ 115 #define preempt_disable() barrier() 116 #define sched_preempt_enable_no_resched() barrier() 117 #define preempt_enable_no_resched() barrier() 118 #define preempt_enable() barrier() 119 #define preempt_check_resched() do { } while (0) 120 121 #define preempt_disable_notrace() barrier() 122 #define preempt_enable_no_resched_notrace() barrier() 123 #define preempt_enable_notrace() barrier() 124 125 #endif /* CONFIG_PREEMPT_COUNT */ 126 127 #ifdef MODULE 128 /* 129 * Modules have no business playing preemption tricks. 130 */ 131 #undef sched_preempt_enable_no_resched 132 #undef preempt_enable_no_resched 133 #undef preempt_enable_no_resched_notrace 134 #undef preempt_check_resched 135 #endif 136 137 #define preempt_set_need_resched() \ 138 do { \ 139 set_preempt_need_resched(); \ 140 } while (0) 141 #define preempt_fold_need_resched() \ 142 do { \ 143 if (tif_need_resched()) \ 144 set_preempt_need_resched(); \ 145 } while (0) 146 147 #ifdef CONFIG_PREEMPT_NOTIFIERS 148 149 struct preempt_notifier; 150 151 /** 152 * preempt_ops - notifiers called when a task is preempted and rescheduled 153 * @sched_in: we're about to be rescheduled: 154 * notifier: struct preempt_notifier for the task being scheduled 155 * cpu: cpu we're scheduled on 156 * @sched_out: we've just been preempted 157 * notifier: struct preempt_notifier for the task being preempted 158 * next: the task that's kicking us out 159 * 160 * Please note that sched_in and out are called under different 161 * contexts. sched_out is called with rq lock held and irq disabled 162 * while sched_in is called without rq lock and irq enabled. This 163 * difference is intentional and depended upon by its users. 164 */ 165 struct preempt_ops { 166 void (*sched_in)(struct preempt_notifier *notifier, int cpu); 167 void (*sched_out)(struct preempt_notifier *notifier, 168 struct task_struct *next); 169 }; 170 171 /** 172 * preempt_notifier - key for installing preemption notifiers 173 * @link: internal use 174 * @ops: defines the notifier functions to be called 175 * 176 * Usually used in conjunction with container_of(). 177 */ 178 struct preempt_notifier { 179 struct hlist_node link; 180 struct preempt_ops *ops; 181 }; 182 183 void preempt_notifier_register(struct preempt_notifier *notifier); 184 void preempt_notifier_unregister(struct preempt_notifier *notifier); 185 preempt_notifier_init(struct preempt_notifier * notifier,struct preempt_ops * ops)186static inline void preempt_notifier_init(struct preempt_notifier *notifier, 187 struct preempt_ops *ops) 188 { 189 INIT_HLIST_NODE(¬ifier->link); 190 notifier->ops = ops; 191 } 192 193 #endif 194 195 #endif /* __LINUX_PREEMPT_H */ 196