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 #if defined(CONFIG_PREEMPT_COUNT) 88 # define PREEMPT_DISABLE_OFFSET 1 89 #else 90 # define PREEMPT_DISABLE_OFFSET 0 91 #endif 92 93 /* 94 * The preempt_count offset needed for things like: 95 * 96 * spin_lock_bh() 97 * 98 * Which need to disable both preemption (CONFIG_PREEMPT_COUNT) and 99 * softirqs, such that unlock sequences of: 100 * 101 * spin_unlock(); 102 * local_bh_enable(); 103 * 104 * Work as expected. 105 */ 106 #define SOFTIRQ_LOCK_OFFSET (SOFTIRQ_DISABLE_OFFSET + PREEMPT_DISABLE_OFFSET) 107 108 /* 109 * Are we running in atomic context? WARNING: this macro cannot 110 * always detect atomic context; in particular, it cannot know about 111 * held spinlocks in non-preemptible kernels. Thus it should not be 112 * used in the general case to determine whether sleeping is possible. 113 * Do not use in_atomic() in driver code. 114 */ 115 #define in_atomic() (preempt_count() != 0) 116 117 /* 118 * Check whether we were atomic before we did preempt_disable(): 119 * (used by the scheduler) 120 */ 121 #define in_atomic_preempt_off() \ 122 ((preempt_count() & ~PREEMPT_ACTIVE) != PREEMPT_DISABLE_OFFSET) 123 124 #if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_PREEMPT_TRACER) 125 extern void preempt_count_add(int val); 126 extern void preempt_count_sub(int val); 127 #define preempt_count_dec_and_test() ({ preempt_count_sub(1); should_resched(); }) 128 #else 129 #define preempt_count_add(val) __preempt_count_add(val) 130 #define preempt_count_sub(val) __preempt_count_sub(val) 131 #define preempt_count_dec_and_test() __preempt_count_dec_and_test() 132 #endif 133 134 #define __preempt_count_inc() __preempt_count_add(1) 135 #define __preempt_count_dec() __preempt_count_sub(1) 136 137 #define preempt_count_inc() preempt_count_add(1) 138 #define preempt_count_dec() preempt_count_sub(1) 139 140 #define preempt_active_enter() \ 141 do { \ 142 preempt_count_add(PREEMPT_ACTIVE + PREEMPT_DISABLE_OFFSET); \ 143 barrier(); \ 144 } while (0) 145 146 #define preempt_active_exit() \ 147 do { \ 148 barrier(); \ 149 preempt_count_sub(PREEMPT_ACTIVE + PREEMPT_DISABLE_OFFSET); \ 150 } while (0) 151 152 #ifdef CONFIG_PREEMPT_COUNT 153 154 #define preempt_disable() \ 155 do { \ 156 preempt_count_inc(); \ 157 barrier(); \ 158 } while (0) 159 160 #define sched_preempt_enable_no_resched() \ 161 do { \ 162 barrier(); \ 163 preempt_count_dec(); \ 164 } while (0) 165 166 #define preempt_enable_no_resched() sched_preempt_enable_no_resched() 167 168 #define preemptible() (preempt_count() == 0 && !irqs_disabled()) 169 170 #ifdef CONFIG_PREEMPT 171 #define preempt_enable() \ 172 do { \ 173 barrier(); \ 174 if (unlikely(preempt_count_dec_and_test())) \ 175 __preempt_schedule(); \ 176 } while (0) 177 178 #define preempt_enable_notrace() \ 179 do { \ 180 barrier(); \ 181 if (unlikely(__preempt_count_dec_and_test())) \ 182 __preempt_schedule_notrace(); \ 183 } while (0) 184 185 #define preempt_check_resched() \ 186 do { \ 187 if (should_resched()) \ 188 __preempt_schedule(); \ 189 } while (0) 190 191 #else /* !CONFIG_PREEMPT */ 192 #define preempt_enable() \ 193 do { \ 194 barrier(); \ 195 preempt_count_dec(); \ 196 } while (0) 197 198 #define preempt_enable_notrace() \ 199 do { \ 200 barrier(); \ 201 __preempt_count_dec(); \ 202 } while (0) 203 204 #define preempt_check_resched() do { } while (0) 205 #endif /* CONFIG_PREEMPT */ 206 207 #define preempt_disable_notrace() \ 208 do { \ 209 __preempt_count_inc(); \ 210 barrier(); \ 211 } while (0) 212 213 #define preempt_enable_no_resched_notrace() \ 214 do { \ 215 barrier(); \ 216 __preempt_count_dec(); \ 217 } while (0) 218 219 #else /* !CONFIG_PREEMPT_COUNT */ 220 221 /* 222 * Even if we don't have any preemption, we need preempt disable/enable 223 * to be barriers, so that we don't have things like get_user/put_user 224 * that can cause faults and scheduling migrate into our preempt-protected 225 * region. 226 */ 227 #define preempt_disable() barrier() 228 #define sched_preempt_enable_no_resched() barrier() 229 #define preempt_enable_no_resched() barrier() 230 #define preempt_enable() barrier() 231 #define preempt_check_resched() do { } while (0) 232 233 #define preempt_disable_notrace() barrier() 234 #define preempt_enable_no_resched_notrace() barrier() 235 #define preempt_enable_notrace() barrier() 236 #define preemptible() 0 237 238 #endif /* CONFIG_PREEMPT_COUNT */ 239 240 #ifdef MODULE 241 /* 242 * Modules have no business playing preemption tricks. 243 */ 244 #undef sched_preempt_enable_no_resched 245 #undef preempt_enable_no_resched 246 #undef preempt_enable_no_resched_notrace 247 #undef preempt_check_resched 248 #endif 249 250 #define preempt_set_need_resched() \ 251 do { \ 252 set_preempt_need_resched(); \ 253 } while (0) 254 #define preempt_fold_need_resched() \ 255 do { \ 256 if (tif_need_resched()) \ 257 set_preempt_need_resched(); \ 258 } while (0) 259 260 #ifdef CONFIG_PREEMPT_NOTIFIERS 261 262 struct preempt_notifier; 263 264 /** 265 * preempt_ops - notifiers called when a task is preempted and rescheduled 266 * @sched_in: we're about to be rescheduled: 267 * notifier: struct preempt_notifier for the task being scheduled 268 * cpu: cpu we're scheduled on 269 * @sched_out: we've just been preempted 270 * notifier: struct preempt_notifier for the task being preempted 271 * next: the task that's kicking us out 272 * 273 * Please note that sched_in and out are called under different 274 * contexts. sched_out is called with rq lock held and irq disabled 275 * while sched_in is called without rq lock and irq enabled. This 276 * difference is intentional and depended upon by its users. 277 */ 278 struct preempt_ops { 279 void (*sched_in)(struct preempt_notifier *notifier, int cpu); 280 void (*sched_out)(struct preempt_notifier *notifier, 281 struct task_struct *next); 282 }; 283 284 /** 285 * preempt_notifier - key for installing preemption notifiers 286 * @link: internal use 287 * @ops: defines the notifier functions to be called 288 * 289 * Usually used in conjunction with container_of(). 290 */ 291 struct preempt_notifier { 292 struct hlist_node link; 293 struct preempt_ops *ops; 294 }; 295 296 void preempt_notifier_inc(void); 297 void preempt_notifier_dec(void); 298 void preempt_notifier_register(struct preempt_notifier *notifier); 299 void preempt_notifier_unregister(struct preempt_notifier *notifier); 300 301 static inline void preempt_notifier_init(struct preempt_notifier *notifier, 302 struct preempt_ops *ops) 303 { 304 INIT_HLIST_NODE(¬ifier->link); 305 notifier->ops = ops; 306 } 307 308 #endif 309 310 #endif /* __LINUX_PREEMPT_H */ 311