1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef __LINUX_PREEMPT_H 3 #define __LINUX_PREEMPT_H 4 5 /* 6 * include/linux/preempt.h - macros for accessing and manipulating 7 * preempt_count (used for kernel preemption, interrupt count, etc.) 8 */ 9 10 #include <linux/linkage.h> 11 #include <linux/list.h> 12 13 /* 14 * We put the hardirq and softirq counter into the preemption 15 * counter. The bitmask has the following meaning: 16 * 17 * - bits 0-7 are the preemption count (max preemption depth: 256) 18 * - bits 8-15 are the softirq count (max # of softirqs: 256) 19 * 20 * The hardirq count could in theory be the same as the number of 21 * interrupts in the system, but we run all interrupt handlers with 22 * interrupts disabled, so we cannot have nesting interrupts. Though 23 * there are a few palaeontologic drivers which reenable interrupts in 24 * the handler, so we need more than one bit here. 25 * 26 * PREEMPT_MASK: 0x000000ff 27 * SOFTIRQ_MASK: 0x0000ff00 28 * HARDIRQ_MASK: 0x000f0000 29 * NMI_MASK: 0x00100000 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 /* We use the MSB mostly because its available */ 57 #define PREEMPT_NEED_RESCHED 0x80000000 58 59 #define PREEMPT_DISABLED (PREEMPT_DISABLE_OFFSET + PREEMPT_ENABLED) 60 61 /* 62 * Disable preemption until the scheduler is running -- use an unconditional 63 * value so that it also works on !PREEMPT_COUNT kernels. 64 * 65 * Reset by start_kernel()->sched_init()->init_idle()->init_idle_preempt_count(). 66 */ 67 #define INIT_PREEMPT_COUNT PREEMPT_OFFSET 68 69 /* 70 * Initial preempt_count value; reflects the preempt_count schedule invariant 71 * which states that during context switches: 72 * 73 * preempt_count() == 2*PREEMPT_DISABLE_OFFSET 74 * 75 * Note: PREEMPT_DISABLE_OFFSET is 0 for !PREEMPT_COUNT kernels. 76 * Note: See finish_task_switch(). 77 */ 78 #define FORK_PREEMPT_COUNT (2*PREEMPT_DISABLE_OFFSET + PREEMPT_ENABLED) 79 80 /* preempt_count() and related functions, depends on PREEMPT_NEED_RESCHED */ 81 #include <asm/preempt.h> 82 83 #define hardirq_count() (preempt_count() & HARDIRQ_MASK) 84 #define softirq_count() (preempt_count() & SOFTIRQ_MASK) 85 #define irq_count() (preempt_count() & (HARDIRQ_MASK | SOFTIRQ_MASK \ 86 | NMI_MASK)) 87 88 /* 89 * Are we doing bottom half or hardware interrupt processing? 90 * 91 * in_irq() - We're in (hard) IRQ context 92 * in_softirq() - We have BH disabled, or are processing softirqs 93 * in_interrupt() - We're in NMI,IRQ,SoftIRQ context or have BH disabled 94 * in_serving_softirq() - We're in softirq context 95 * in_nmi() - We're in NMI context 96 * in_task() - We're in task context 97 * 98 * Note: due to the BH disabled confusion: in_softirq(),in_interrupt() really 99 * should not be used in new code. 100 */ 101 #define in_irq() (hardirq_count()) 102 #define in_softirq() (softirq_count()) 103 #define in_interrupt() (irq_count()) 104 #define in_serving_softirq() (softirq_count() & SOFTIRQ_OFFSET) 105 #define in_nmi() (preempt_count() & NMI_MASK) 106 #define in_task() (!(preempt_count() & \ 107 (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET))) 108 109 /* 110 * The preempt_count offset after preempt_disable(); 111 */ 112 #if defined(CONFIG_PREEMPT_COUNT) 113 # define PREEMPT_DISABLE_OFFSET PREEMPT_OFFSET 114 #else 115 # define PREEMPT_DISABLE_OFFSET 0 116 #endif 117 118 /* 119 * The preempt_count offset after spin_lock() 120 */ 121 #define PREEMPT_LOCK_OFFSET PREEMPT_DISABLE_OFFSET 122 123 /* 124 * The preempt_count offset needed for things like: 125 * 126 * spin_lock_bh() 127 * 128 * Which need to disable both preemption (CONFIG_PREEMPT_COUNT) and 129 * softirqs, such that unlock sequences of: 130 * 131 * spin_unlock(); 132 * local_bh_enable(); 133 * 134 * Work as expected. 135 */ 136 #define SOFTIRQ_LOCK_OFFSET (SOFTIRQ_DISABLE_OFFSET + PREEMPT_LOCK_OFFSET) 137 138 /* 139 * Are we running in atomic context? WARNING: this macro cannot 140 * always detect atomic context; in particular, it cannot know about 141 * held spinlocks in non-preemptible kernels. Thus it should not be 142 * used in the general case to determine whether sleeping is possible. 143 * Do not use in_atomic() in driver code. 144 */ 145 #define in_atomic() (preempt_count() != 0) 146 147 /* 148 * Check whether we were atomic before we did preempt_disable(): 149 * (used by the scheduler) 150 */ 151 #define in_atomic_preempt_off() (preempt_count() != PREEMPT_DISABLE_OFFSET) 152 153 #if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_PREEMPT_TRACER) 154 extern void preempt_count_add(int val); 155 extern void preempt_count_sub(int val); 156 #define preempt_count_dec_and_test() \ 157 ({ preempt_count_sub(1); should_resched(0); }) 158 #else 159 #define preempt_count_add(val) __preempt_count_add(val) 160 #define preempt_count_sub(val) __preempt_count_sub(val) 161 #define preempt_count_dec_and_test() __preempt_count_dec_and_test() 162 #endif 163 164 #define __preempt_count_inc() __preempt_count_add(1) 165 #define __preempt_count_dec() __preempt_count_sub(1) 166 167 #define preempt_count_inc() preempt_count_add(1) 168 #define preempt_count_dec() preempt_count_sub(1) 169 170 #ifdef CONFIG_PREEMPT_COUNT 171 172 #define preempt_disable() \ 173 do { \ 174 preempt_count_inc(); \ 175 barrier(); \ 176 } while (0) 177 178 #define sched_preempt_enable_no_resched() \ 179 do { \ 180 barrier(); \ 181 preempt_count_dec(); \ 182 } while (0) 183 184 #define preempt_enable_no_resched() sched_preempt_enable_no_resched() 185 186 #define preemptible() (preempt_count() == 0 && !irqs_disabled()) 187 188 #ifdef CONFIG_PREEMPT 189 #define preempt_enable() \ 190 do { \ 191 barrier(); \ 192 if (unlikely(preempt_count_dec_and_test())) \ 193 __preempt_schedule(); \ 194 } while (0) 195 196 #define preempt_enable_notrace() \ 197 do { \ 198 barrier(); \ 199 if (unlikely(__preempt_count_dec_and_test())) \ 200 __preempt_schedule_notrace(); \ 201 } while (0) 202 203 #define preempt_check_resched() \ 204 do { \ 205 if (should_resched(0)) \ 206 __preempt_schedule(); \ 207 } while (0) 208 209 #else /* !CONFIG_PREEMPT */ 210 #define preempt_enable() \ 211 do { \ 212 barrier(); \ 213 preempt_count_dec(); \ 214 } while (0) 215 216 #define preempt_enable_notrace() \ 217 do { \ 218 barrier(); \ 219 __preempt_count_dec(); \ 220 } while (0) 221 222 #define preempt_check_resched() do { } while (0) 223 #endif /* CONFIG_PREEMPT */ 224 225 #define preempt_disable_notrace() \ 226 do { \ 227 __preempt_count_inc(); \ 228 barrier(); \ 229 } while (0) 230 231 #define preempt_enable_no_resched_notrace() \ 232 do { \ 233 barrier(); \ 234 __preempt_count_dec(); \ 235 } while (0) 236 237 #else /* !CONFIG_PREEMPT_COUNT */ 238 239 /* 240 * Even if we don't have any preemption, we need preempt disable/enable 241 * to be barriers, so that we don't have things like get_user/put_user 242 * that can cause faults and scheduling migrate into our preempt-protected 243 * region. 244 */ 245 #define preempt_disable() barrier() 246 #define sched_preempt_enable_no_resched() barrier() 247 #define preempt_enable_no_resched() barrier() 248 #define preempt_enable() barrier() 249 #define preempt_check_resched() do { } while (0) 250 251 #define preempt_disable_notrace() barrier() 252 #define preempt_enable_no_resched_notrace() barrier() 253 #define preempt_enable_notrace() barrier() 254 #define preemptible() 0 255 256 #endif /* CONFIG_PREEMPT_COUNT */ 257 258 #ifdef MODULE 259 /* 260 * Modules have no business playing preemption tricks. 261 */ 262 #undef sched_preempt_enable_no_resched 263 #undef preempt_enable_no_resched 264 #undef preempt_enable_no_resched_notrace 265 #undef preempt_check_resched 266 #endif 267 268 #define preempt_set_need_resched() \ 269 do { \ 270 set_preempt_need_resched(); \ 271 } while (0) 272 #define preempt_fold_need_resched() \ 273 do { \ 274 if (tif_need_resched()) \ 275 set_preempt_need_resched(); \ 276 } while (0) 277 278 #ifdef CONFIG_PREEMPT_NOTIFIERS 279 280 struct preempt_notifier; 281 282 /** 283 * preempt_ops - notifiers called when a task is preempted and rescheduled 284 * @sched_in: we're about to be rescheduled: 285 * notifier: struct preempt_notifier for the task being scheduled 286 * cpu: cpu we're scheduled on 287 * @sched_out: we've just been preempted 288 * notifier: struct preempt_notifier for the task being preempted 289 * next: the task that's kicking us out 290 * 291 * Please note that sched_in and out are called under different 292 * contexts. sched_out is called with rq lock held and irq disabled 293 * while sched_in is called without rq lock and irq enabled. This 294 * difference is intentional and depended upon by its users. 295 */ 296 struct preempt_ops { 297 void (*sched_in)(struct preempt_notifier *notifier, int cpu); 298 void (*sched_out)(struct preempt_notifier *notifier, 299 struct task_struct *next); 300 }; 301 302 /** 303 * preempt_notifier - key for installing preemption notifiers 304 * @link: internal use 305 * @ops: defines the notifier functions to be called 306 * 307 * Usually used in conjunction with container_of(). 308 */ 309 struct preempt_notifier { 310 struct hlist_node link; 311 struct preempt_ops *ops; 312 }; 313 314 void preempt_notifier_inc(void); 315 void preempt_notifier_dec(void); 316 void preempt_notifier_register(struct preempt_notifier *notifier); 317 void preempt_notifier_unregister(struct preempt_notifier *notifier); 318 319 static inline void preempt_notifier_init(struct preempt_notifier *notifier, 320 struct preempt_ops *ops) 321 { 322 INIT_HLIST_NODE(¬ifier->link); 323 notifier->ops = ops; 324 } 325 326 #endif 327 328 #endif /* __LINUX_PREEMPT_H */ 329