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_ACTIVE: 0x00200000 30 * PREEMPT_NEED_RESCHED: 0x80000000 31 */ 32 #define PREEMPT_BITS 8 33 #define SOFTIRQ_BITS 8 34 #define HARDIRQ_BITS 4 35 #define NMI_BITS 1 36 37 #define PREEMPT_SHIFT 0 38 #define SOFTIRQ_SHIFT (PREEMPT_SHIFT + PREEMPT_BITS) 39 #define HARDIRQ_SHIFT (SOFTIRQ_SHIFT + SOFTIRQ_BITS) 40 #define NMI_SHIFT (HARDIRQ_SHIFT + HARDIRQ_BITS) 41 42 #define __IRQ_MASK(x) ((1UL << (x))-1) 43 44 #define PREEMPT_MASK (__IRQ_MASK(PREEMPT_BITS) << PREEMPT_SHIFT) 45 #define SOFTIRQ_MASK (__IRQ_MASK(SOFTIRQ_BITS) << SOFTIRQ_SHIFT) 46 #define HARDIRQ_MASK (__IRQ_MASK(HARDIRQ_BITS) << HARDIRQ_SHIFT) 47 #define NMI_MASK (__IRQ_MASK(NMI_BITS) << NMI_SHIFT) 48 49 #define PREEMPT_OFFSET (1UL << PREEMPT_SHIFT) 50 #define SOFTIRQ_OFFSET (1UL << SOFTIRQ_SHIFT) 51 #define HARDIRQ_OFFSET (1UL << HARDIRQ_SHIFT) 52 #define NMI_OFFSET (1UL << NMI_SHIFT) 53 54 #define SOFTIRQ_DISABLE_OFFSET (2 * SOFTIRQ_OFFSET) 55 56 #define PREEMPT_ACTIVE_BITS 1 57 #define PREEMPT_ACTIVE_SHIFT (NMI_SHIFT + NMI_BITS) 58 #define PREEMPT_ACTIVE (__IRQ_MASK(PREEMPT_ACTIVE_BITS) << PREEMPT_ACTIVE_SHIFT) 59 60 /* We use the MSB mostly because its available */ 61 #define PREEMPT_NEED_RESCHED 0x80000000 62 63 /* preempt_count() and related functions, depends on PREEMPT_NEED_RESCHED */ 64 #include <asm/preempt.h> 65 66 #define hardirq_count() (preempt_count() & HARDIRQ_MASK) 67 #define softirq_count() (preempt_count() & SOFTIRQ_MASK) 68 #define irq_count() (preempt_count() & (HARDIRQ_MASK | SOFTIRQ_MASK \ 69 | NMI_MASK)) 70 71 /* 72 * Are we doing bottom half or hardware interrupt processing? 73 * Are we in a softirq context? Interrupt context? 74 * in_softirq - Are we currently processing softirq or have bh disabled? 75 * in_serving_softirq - Are we currently processing softirq? 76 */ 77 #define in_irq() (hardirq_count()) 78 #define in_softirq() (softirq_count()) 79 #define in_interrupt() (irq_count()) 80 #define in_serving_softirq() (softirq_count() & SOFTIRQ_OFFSET) 81 82 /* 83 * Are we in NMI context? 84 */ 85 #define in_nmi() (preempt_count() & NMI_MASK) 86 87 /* 88 * The preempt_count offset after preempt_disable(); 89 */ 90 #if defined(CONFIG_PREEMPT_COUNT) 91 # define PREEMPT_DISABLE_OFFSET PREEMPT_OFFSET 92 #else 93 # define PREEMPT_DISABLE_OFFSET 0 94 #endif 95 96 /* 97 * The preempt_count offset after spin_lock() 98 */ 99 #define PREEMPT_LOCK_OFFSET PREEMPT_DISABLE_OFFSET 100 101 /* 102 * The preempt_count offset needed for things like: 103 * 104 * spin_lock_bh() 105 * 106 * Which need to disable both preemption (CONFIG_PREEMPT_COUNT) and 107 * softirqs, such that unlock sequences of: 108 * 109 * spin_unlock(); 110 * local_bh_enable(); 111 * 112 * Work as expected. 113 */ 114 #define SOFTIRQ_LOCK_OFFSET (SOFTIRQ_DISABLE_OFFSET + PREEMPT_LOCK_OFFSET) 115 116 /* 117 * Are we running in atomic context? WARNING: this macro cannot 118 * always detect atomic context; in particular, it cannot know about 119 * held spinlocks in non-preemptible kernels. Thus it should not be 120 * used in the general case to determine whether sleeping is possible. 121 * Do not use in_atomic() in driver code. 122 */ 123 #define in_atomic() (preempt_count() != 0) 124 125 /* 126 * Check whether we were atomic before we did preempt_disable(): 127 * (used by the scheduler) 128 */ 129 #define in_atomic_preempt_off() \ 130 ((preempt_count() & ~PREEMPT_ACTIVE) != PREEMPT_DISABLE_OFFSET) 131 132 #if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_PREEMPT_TRACER) 133 extern void preempt_count_add(int val); 134 extern void preempt_count_sub(int val); 135 #define preempt_count_dec_and_test() \ 136 ({ preempt_count_sub(1); should_resched(0); }) 137 #else 138 #define preempt_count_add(val) __preempt_count_add(val) 139 #define preempt_count_sub(val) __preempt_count_sub(val) 140 #define preempt_count_dec_and_test() __preempt_count_dec_and_test() 141 #endif 142 143 #define __preempt_count_inc() __preempt_count_add(1) 144 #define __preempt_count_dec() __preempt_count_sub(1) 145 146 #define preempt_count_inc() preempt_count_add(1) 147 #define preempt_count_dec() preempt_count_sub(1) 148 149 #define preempt_active_enter() \ 150 do { \ 151 preempt_count_add(PREEMPT_ACTIVE + PREEMPT_DISABLE_OFFSET); \ 152 barrier(); \ 153 } while (0) 154 155 #define preempt_active_exit() \ 156 do { \ 157 barrier(); \ 158 preempt_count_sub(PREEMPT_ACTIVE + PREEMPT_DISABLE_OFFSET); \ 159 } while (0) 160 161 #ifdef CONFIG_PREEMPT_COUNT 162 163 #define preempt_disable() \ 164 do { \ 165 preempt_count_inc(); \ 166 barrier(); \ 167 } while (0) 168 169 #define sched_preempt_enable_no_resched() \ 170 do { \ 171 barrier(); \ 172 preempt_count_dec(); \ 173 } while (0) 174 175 #define preempt_enable_no_resched() sched_preempt_enable_no_resched() 176 177 #define preemptible() (preempt_count() == 0 && !irqs_disabled()) 178 179 #ifdef CONFIG_PREEMPT 180 #define preempt_enable() \ 181 do { \ 182 barrier(); \ 183 if (unlikely(preempt_count_dec_and_test())) \ 184 __preempt_schedule(); \ 185 } while (0) 186 187 #define preempt_enable_notrace() \ 188 do { \ 189 barrier(); \ 190 if (unlikely(__preempt_count_dec_and_test())) \ 191 __preempt_schedule_notrace(); \ 192 } while (0) 193 194 #define preempt_check_resched() \ 195 do { \ 196 if (should_resched(0)) \ 197 __preempt_schedule(); \ 198 } while (0) 199 200 #else /* !CONFIG_PREEMPT */ 201 #define preempt_enable() \ 202 do { \ 203 barrier(); \ 204 preempt_count_dec(); \ 205 } while (0) 206 207 #define preempt_enable_notrace() \ 208 do { \ 209 barrier(); \ 210 __preempt_count_dec(); \ 211 } while (0) 212 213 #define preempt_check_resched() do { } while (0) 214 #endif /* CONFIG_PREEMPT */ 215 216 #define preempt_disable_notrace() \ 217 do { \ 218 __preempt_count_inc(); \ 219 barrier(); \ 220 } while (0) 221 222 #define preempt_enable_no_resched_notrace() \ 223 do { \ 224 barrier(); \ 225 __preempt_count_dec(); \ 226 } while (0) 227 228 #else /* !CONFIG_PREEMPT_COUNT */ 229 230 /* 231 * Even if we don't have any preemption, we need preempt disable/enable 232 * to be barriers, so that we don't have things like get_user/put_user 233 * that can cause faults and scheduling migrate into our preempt-protected 234 * region. 235 */ 236 #define preempt_disable() barrier() 237 #define sched_preempt_enable_no_resched() barrier() 238 #define preempt_enable_no_resched() barrier() 239 #define preempt_enable() barrier() 240 #define preempt_check_resched() do { } while (0) 241 242 #define preempt_disable_notrace() barrier() 243 #define preempt_enable_no_resched_notrace() barrier() 244 #define preempt_enable_notrace() barrier() 245 #define preemptible() 0 246 247 #endif /* CONFIG_PREEMPT_COUNT */ 248 249 #ifdef MODULE 250 /* 251 * Modules have no business playing preemption tricks. 252 */ 253 #undef sched_preempt_enable_no_resched 254 #undef preempt_enable_no_resched 255 #undef preempt_enable_no_resched_notrace 256 #undef preempt_check_resched 257 #endif 258 259 #define preempt_set_need_resched() \ 260 do { \ 261 set_preempt_need_resched(); \ 262 } while (0) 263 #define preempt_fold_need_resched() \ 264 do { \ 265 if (tif_need_resched()) \ 266 set_preempt_need_resched(); \ 267 } while (0) 268 269 #ifdef CONFIG_PREEMPT_NOTIFIERS 270 271 struct preempt_notifier; 272 273 /** 274 * preempt_ops - notifiers called when a task is preempted and rescheduled 275 * @sched_in: we're about to be rescheduled: 276 * notifier: struct preempt_notifier for the task being scheduled 277 * cpu: cpu we're scheduled on 278 * @sched_out: we've just been preempted 279 * notifier: struct preempt_notifier for the task being preempted 280 * next: the task that's kicking us out 281 * 282 * Please note that sched_in and out are called under different 283 * contexts. sched_out is called with rq lock held and irq disabled 284 * while sched_in is called without rq lock and irq enabled. This 285 * difference is intentional and depended upon by its users. 286 */ 287 struct preempt_ops { 288 void (*sched_in)(struct preempt_notifier *notifier, int cpu); 289 void (*sched_out)(struct preempt_notifier *notifier, 290 struct task_struct *next); 291 }; 292 293 /** 294 * preempt_notifier - key for installing preemption notifiers 295 * @link: internal use 296 * @ops: defines the notifier functions to be called 297 * 298 * Usually used in conjunction with container_of(). 299 */ 300 struct preempt_notifier { 301 struct hlist_node link; 302 struct preempt_ops *ops; 303 }; 304 305 void preempt_notifier_inc(void); 306 void preempt_notifier_dec(void); 307 void preempt_notifier_register(struct preempt_notifier *notifier); 308 void preempt_notifier_unregister(struct preempt_notifier *notifier); 309 310 static inline void preempt_notifier_init(struct preempt_notifier *notifier, 311 struct preempt_ops *ops) 312 { 313 INIT_HLIST_NODE(¬ifier->link); 314 notifier->ops = ops; 315 } 316 317 #endif 318 319 #endif /* __LINUX_PREEMPT_H */ 320