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 put the hardirq and softirq counter into the preemption 14 * counter. The bitmask has the following meaning: 15 * 16 * - bits 0-7 are the preemption count (max preemption depth: 256) 17 * - bits 8-15 are the softirq count (max # of softirqs: 256) 18 * 19 * The hardirq count could in theory be the same as the number of 20 * interrupts in the system, but we run all interrupt handlers with 21 * interrupts disabled, so we cannot have nesting interrupts. Though 22 * there are a few palaeontologic drivers which reenable interrupts in 23 * the handler, so we need more than one bit here. 24 * 25 * PREEMPT_MASK: 0x000000ff 26 * SOFTIRQ_MASK: 0x0000ff00 27 * HARDIRQ_MASK: 0x000f0000 28 * NMI_MASK: 0x00100000 29 * PREEMPT_NEED_RESCHED: 0x80000000 30 */ 31 #define PREEMPT_BITS 8 32 #define SOFTIRQ_BITS 8 33 #define HARDIRQ_BITS 4 34 #define NMI_BITS 1 35 36 #define PREEMPT_SHIFT 0 37 #define SOFTIRQ_SHIFT (PREEMPT_SHIFT + PREEMPT_BITS) 38 #define HARDIRQ_SHIFT (SOFTIRQ_SHIFT + SOFTIRQ_BITS) 39 #define NMI_SHIFT (HARDIRQ_SHIFT + HARDIRQ_BITS) 40 41 #define __IRQ_MASK(x) ((1UL << (x))-1) 42 43 #define PREEMPT_MASK (__IRQ_MASK(PREEMPT_BITS) << PREEMPT_SHIFT) 44 #define SOFTIRQ_MASK (__IRQ_MASK(SOFTIRQ_BITS) << SOFTIRQ_SHIFT) 45 #define HARDIRQ_MASK (__IRQ_MASK(HARDIRQ_BITS) << HARDIRQ_SHIFT) 46 #define NMI_MASK (__IRQ_MASK(NMI_BITS) << NMI_SHIFT) 47 48 #define PREEMPT_OFFSET (1UL << PREEMPT_SHIFT) 49 #define SOFTIRQ_OFFSET (1UL << SOFTIRQ_SHIFT) 50 #define HARDIRQ_OFFSET (1UL << HARDIRQ_SHIFT) 51 #define NMI_OFFSET (1UL << NMI_SHIFT) 52 53 #define SOFTIRQ_DISABLE_OFFSET (2 * SOFTIRQ_OFFSET) 54 55 /* We use the MSB mostly because its available */ 56 #define PREEMPT_NEED_RESCHED 0x80000000 57 58 /* preempt_count() and related functions, depends on PREEMPT_NEED_RESCHED */ 59 #include <asm/preempt.h> 60 61 #define hardirq_count() (preempt_count() & HARDIRQ_MASK) 62 #define softirq_count() (preempt_count() & SOFTIRQ_MASK) 63 #define irq_count() (preempt_count() & (HARDIRQ_MASK | SOFTIRQ_MASK \ 64 | NMI_MASK)) 65 66 /* 67 * Are we doing bottom half or hardware interrupt processing? 68 * Are we in a softirq context? Interrupt context? 69 * in_softirq - Are we currently processing softirq or have bh disabled? 70 * in_serving_softirq - Are we currently processing softirq? 71 */ 72 #define in_irq() (hardirq_count()) 73 #define in_softirq() (softirq_count()) 74 #define in_interrupt() (irq_count()) 75 #define in_serving_softirq() (softirq_count() & SOFTIRQ_OFFSET) 76 77 /* 78 * Are we in NMI context? 79 */ 80 #define in_nmi() (preempt_count() & NMI_MASK) 81 82 /* 83 * The preempt_count offset after preempt_disable(); 84 */ 85 #if defined(CONFIG_PREEMPT_COUNT) 86 # define PREEMPT_DISABLE_OFFSET PREEMPT_OFFSET 87 #else 88 # define PREEMPT_DISABLE_OFFSET 0 89 #endif 90 91 /* 92 * The preempt_count offset after spin_lock() 93 */ 94 #define PREEMPT_LOCK_OFFSET PREEMPT_DISABLE_OFFSET 95 96 /* 97 * The preempt_count offset needed for things like: 98 * 99 * spin_lock_bh() 100 * 101 * Which need to disable both preemption (CONFIG_PREEMPT_COUNT) and 102 * softirqs, such that unlock sequences of: 103 * 104 * spin_unlock(); 105 * local_bh_enable(); 106 * 107 * Work as expected. 108 */ 109 #define SOFTIRQ_LOCK_OFFSET (SOFTIRQ_DISABLE_OFFSET + PREEMPT_LOCK_OFFSET) 110 111 /* 112 * Are we running in atomic context? WARNING: this macro cannot 113 * always detect atomic context; in particular, it cannot know about 114 * held spinlocks in non-preemptible kernels. Thus it should not be 115 * used in the general case to determine whether sleeping is possible. 116 * Do not use in_atomic() in driver code. 117 */ 118 #define in_atomic() (preempt_count() != 0) 119 120 /* 121 * Check whether we were atomic before we did preempt_disable(): 122 * (used by the scheduler) 123 */ 124 #define in_atomic_preempt_off() (preempt_count() != PREEMPT_DISABLE_OFFSET) 125 126 #if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_PREEMPT_TRACER) 127 extern void preempt_count_add(int val); 128 extern void preempt_count_sub(int val); 129 #define preempt_count_dec_and_test() \ 130 ({ preempt_count_sub(1); should_resched(0); }) 131 #else 132 #define preempt_count_add(val) __preempt_count_add(val) 133 #define preempt_count_sub(val) __preempt_count_sub(val) 134 #define preempt_count_dec_and_test() __preempt_count_dec_and_test() 135 #endif 136 137 #define __preempt_count_inc() __preempt_count_add(1) 138 #define __preempt_count_dec() __preempt_count_sub(1) 139 140 #define preempt_count_inc() preempt_count_add(1) 141 #define preempt_count_dec() preempt_count_sub(1) 142 143 #ifdef CONFIG_PREEMPT_COUNT 144 145 #define preempt_disable() \ 146 do { \ 147 preempt_count_inc(); \ 148 barrier(); \ 149 } while (0) 150 151 #define sched_preempt_enable_no_resched() \ 152 do { \ 153 barrier(); \ 154 preempt_count_dec(); \ 155 } while (0) 156 157 #define preempt_enable_no_resched() sched_preempt_enable_no_resched() 158 159 #define preemptible() (preempt_count() == 0 && !irqs_disabled()) 160 161 #ifdef CONFIG_PREEMPT 162 #define preempt_enable() \ 163 do { \ 164 barrier(); \ 165 if (unlikely(preempt_count_dec_and_test())) \ 166 __preempt_schedule(); \ 167 } while (0) 168 169 #define preempt_enable_notrace() \ 170 do { \ 171 barrier(); \ 172 if (unlikely(__preempt_count_dec_and_test())) \ 173 __preempt_schedule_notrace(); \ 174 } while (0) 175 176 #define preempt_check_resched() \ 177 do { \ 178 if (should_resched(0)) \ 179 __preempt_schedule(); \ 180 } while (0) 181 182 #else /* !CONFIG_PREEMPT */ 183 #define preempt_enable() \ 184 do { \ 185 barrier(); \ 186 preempt_count_dec(); \ 187 } while (0) 188 189 #define preempt_enable_notrace() \ 190 do { \ 191 barrier(); \ 192 __preempt_count_dec(); \ 193 } while (0) 194 195 #define preempt_check_resched() do { } while (0) 196 #endif /* CONFIG_PREEMPT */ 197 198 #define preempt_disable_notrace() \ 199 do { \ 200 __preempt_count_inc(); \ 201 barrier(); \ 202 } while (0) 203 204 #define preempt_enable_no_resched_notrace() \ 205 do { \ 206 barrier(); \ 207 __preempt_count_dec(); \ 208 } while (0) 209 210 #else /* !CONFIG_PREEMPT_COUNT */ 211 212 /* 213 * Even if we don't have any preemption, we need preempt disable/enable 214 * to be barriers, so that we don't have things like get_user/put_user 215 * that can cause faults and scheduling migrate into our preempt-protected 216 * region. 217 */ 218 #define preempt_disable() barrier() 219 #define sched_preempt_enable_no_resched() barrier() 220 #define preempt_enable_no_resched() barrier() 221 #define preempt_enable() barrier() 222 #define preempt_check_resched() do { } while (0) 223 224 #define preempt_disable_notrace() barrier() 225 #define preempt_enable_no_resched_notrace() barrier() 226 #define preempt_enable_notrace() barrier() 227 #define preemptible() 0 228 229 #endif /* CONFIG_PREEMPT_COUNT */ 230 231 #ifdef MODULE 232 /* 233 * Modules have no business playing preemption tricks. 234 */ 235 #undef sched_preempt_enable_no_resched 236 #undef preempt_enable_no_resched 237 #undef preempt_enable_no_resched_notrace 238 #undef preempt_check_resched 239 #endif 240 241 #define preempt_set_need_resched() \ 242 do { \ 243 set_preempt_need_resched(); \ 244 } while (0) 245 #define preempt_fold_need_resched() \ 246 do { \ 247 if (tif_need_resched()) \ 248 set_preempt_need_resched(); \ 249 } while (0) 250 251 #ifdef CONFIG_PREEMPT_NOTIFIERS 252 253 struct preempt_notifier; 254 255 /** 256 * preempt_ops - notifiers called when a task is preempted and rescheduled 257 * @sched_in: we're about to be rescheduled: 258 * notifier: struct preempt_notifier for the task being scheduled 259 * cpu: cpu we're scheduled on 260 * @sched_out: we've just been preempted 261 * notifier: struct preempt_notifier for the task being preempted 262 * next: the task that's kicking us out 263 * 264 * Please note that sched_in and out are called under different 265 * contexts. sched_out is called with rq lock held and irq disabled 266 * while sched_in is called without rq lock and irq enabled. This 267 * difference is intentional and depended upon by its users. 268 */ 269 struct preempt_ops { 270 void (*sched_in)(struct preempt_notifier *notifier, int cpu); 271 void (*sched_out)(struct preempt_notifier *notifier, 272 struct task_struct *next); 273 }; 274 275 /** 276 * preempt_notifier - key for installing preemption notifiers 277 * @link: internal use 278 * @ops: defines the notifier functions to be called 279 * 280 * Usually used in conjunction with container_of(). 281 */ 282 struct preempt_notifier { 283 struct hlist_node link; 284 struct preempt_ops *ops; 285 }; 286 287 void preempt_notifier_inc(void); 288 void preempt_notifier_dec(void); 289 void preempt_notifier_register(struct preempt_notifier *notifier); 290 void preempt_notifier_unregister(struct preempt_notifier *notifier); 291 292 static inline void preempt_notifier_init(struct preempt_notifier *notifier, 293 struct preempt_ops *ops) 294 { 295 INIT_HLIST_NODE(¬ifier->link); 296 notifier->ops = ops; 297 } 298 299 #endif 300 301 #endif /* __LINUX_PREEMPT_H */ 302