| 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: 0x00f00000 |
| 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 4 |
| 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_DISABLED (PREEMPT_DISABLE_OFFSET + PREEMPT_ENABLED) |
| 57 | |
| 58 | /* |
| 59 | * Disable preemption until the scheduler is running -- use an unconditional |
| 60 | * value so that it also works on !PREEMPT_COUNT kernels. |
| 61 | * |
| 62 | * Reset by start_kernel()->sched_init()->init_idle()->init_idle_preempt_count(). |
| 63 | */ |
| 64 | #define INIT_PREEMPT_COUNT PREEMPT_OFFSET |
| 65 | |
| 66 | /* |
| 67 | * Initial preempt_count value; reflects the preempt_count schedule invariant |
| 68 | * which states that during context switches: |
| 69 | * |
| 70 | * preempt_count() == 2*PREEMPT_DISABLE_OFFSET |
| 71 | * |
| 72 | * Note: PREEMPT_DISABLE_OFFSET is 0 for !PREEMPT_COUNT kernels. |
| 73 | * Note: See finish_task_switch(). |
| 74 | */ |
| 75 | #define FORK_PREEMPT_COUNT (2*PREEMPT_DISABLE_OFFSET + PREEMPT_ENABLED) |
| 76 | |
| 77 | /* preempt_count() and related functions, depends on PREEMPT_NEED_RESCHED */ |
| 78 | #include <asm/preempt.h> |
| 79 | |
| 80 | #define hardirq_count() (preempt_count() & HARDIRQ_MASK) |
| 81 | #define softirq_count() (preempt_count() & SOFTIRQ_MASK) |
| 82 | #define irq_count() (preempt_count() & (HARDIRQ_MASK | SOFTIRQ_MASK \ |
| 83 | | NMI_MASK)) |
| 84 | |
| 85 | /* |
| 86 | * Are we doing bottom half or hardware interrupt processing? |
| 87 | * |
| 88 | * in_irq() - We're in (hard) IRQ context |
| 89 | * in_softirq() - We have BH disabled, or are processing softirqs |
| 90 | * in_interrupt() - We're in NMI,IRQ,SoftIRQ context or have BH disabled |
| 91 | * in_serving_softirq() - We're in softirq context |
| 92 | * in_nmi() - We're in NMI context |
| 93 | * in_task() - We're in task context |
| 94 | * |
| 95 | * Note: due to the BH disabled confusion: in_softirq(),in_interrupt() really |
| 96 | * should not be used in new code. |
| 97 | */ |
| 98 | #define in_irq() (hardirq_count()) |
| 99 | #define in_softirq() (softirq_count()) |
| 100 | #define in_interrupt() (irq_count()) |
| 101 | #define in_serving_softirq() (softirq_count() & SOFTIRQ_OFFSET) |
| 102 | #define in_nmi() (preempt_count() & NMI_MASK) |
| 103 | #define in_task() (!(preempt_count() & \ |
| 104 | (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET))) |
| 105 | |
| 106 | /* |
| 107 | * The preempt_count offset after preempt_disable(); |
| 108 | */ |
| 109 | #if defined(CONFIG_PREEMPT_COUNT) |
| 110 | # define PREEMPT_DISABLE_OFFSET PREEMPT_OFFSET |
| 111 | #else |
| 112 | # define PREEMPT_DISABLE_OFFSET 0 |
| 113 | #endif |
| 114 | |
| 115 | /* |
| 116 | * The preempt_count offset after spin_lock() |
| 117 | */ |
| 118 | #define PREEMPT_LOCK_OFFSET PREEMPT_DISABLE_OFFSET |
| 119 | |
| 120 | /* |
| 121 | * The preempt_count offset needed for things like: |
| 122 | * |
| 123 | * spin_lock_bh() |
| 124 | * |
| 125 | * Which need to disable both preemption (CONFIG_PREEMPT_COUNT) and |
| 126 | * softirqs, such that unlock sequences of: |
| 127 | * |
| 128 | * spin_unlock(); |
| 129 | * local_bh_enable(); |
| 130 | * |
| 131 | * Work as expected. |
| 132 | */ |
| 133 | #define SOFTIRQ_LOCK_OFFSET (SOFTIRQ_DISABLE_OFFSET + PREEMPT_LOCK_OFFSET) |
| 134 | |
| 135 | /* |
| 136 | * Are we running in atomic context? WARNING: this macro cannot |
| 137 | * always detect atomic context; in particular, it cannot know about |
| 138 | * held spinlocks in non-preemptible kernels. Thus it should not be |
| 139 | * used in the general case to determine whether sleeping is possible. |
| 140 | * Do not use in_atomic() in driver code. |
| 141 | */ |
| 142 | #define in_atomic() (preempt_count() != 0) |
| 143 | |
| 144 | /* |
| 145 | * Check whether we were atomic before we did preempt_disable(): |
| 146 | * (used by the scheduler) |
| 147 | */ |
| 148 | #define in_atomic_preempt_off() (preempt_count() != PREEMPT_DISABLE_OFFSET) |
| 149 | |
| 150 | #if defined(CONFIG_DEBUG_PREEMPT) || defined(CONFIG_TRACE_PREEMPT_TOGGLE) |
| 151 | extern void preempt_count_add(int val); |
| 152 | extern void preempt_count_sub(int val); |
| 153 | #define preempt_count_dec_and_test() \ |
| 154 | ({ preempt_count_sub(1); should_resched(0); }) |
| 155 | #else |
| 156 | #define preempt_count_add(val) __preempt_count_add(val) |
| 157 | #define preempt_count_sub(val) __preempt_count_sub(val) |
| 158 | #define preempt_count_dec_and_test() __preempt_count_dec_and_test() |
| 159 | #endif |
| 160 | |
| 161 | #define __preempt_count_inc() __preempt_count_add(1) |
| 162 | #define __preempt_count_dec() __preempt_count_sub(1) |
| 163 | |
| 164 | #define preempt_count_inc() preempt_count_add(1) |
| 165 | #define preempt_count_dec() preempt_count_sub(1) |
| 166 | |
| 167 | #ifdef CONFIG_PREEMPT_COUNT |
| 168 | |
| 169 | #define preempt_disable() \ |
| 170 | do { \ |
| 171 | preempt_count_inc(); \ |
| 172 | barrier(); \ |
| 173 | } while (0) |
| 174 | |
| 175 | #define sched_preempt_enable_no_resched() \ |
| 176 | do { \ |
| 177 | barrier(); \ |
| 178 | preempt_count_dec(); \ |
| 179 | } while (0) |
| 180 | |
| 181 | #define preempt_enable_no_resched() sched_preempt_enable_no_resched() |
| 182 | |
| 183 | #define preemptible() (preempt_count() == 0 && !irqs_disabled()) |
| 184 | |
| 185 | #ifdef CONFIG_PREEMPTION |
| 186 | #define preempt_enable() \ |
| 187 | do { \ |
| 188 | barrier(); \ |
| 189 | if (unlikely(preempt_count_dec_and_test())) \ |
| 190 | __preempt_schedule(); \ |
| 191 | } while (0) |
| 192 | |
| 193 | #define preempt_enable_notrace() \ |
| 194 | do { \ |
| 195 | barrier(); \ |
| 196 | if (unlikely(__preempt_count_dec_and_test())) \ |
| 197 | __preempt_schedule_notrace(); \ |
| 198 | } while (0) |
| 199 | |
| 200 | #define preempt_check_resched() \ |
| 201 | do { \ |
| 202 | if (should_resched(0)) \ |
| 203 | __preempt_schedule(); \ |
| 204 | } while (0) |
| 205 | |
| 206 | #else /* !CONFIG_PREEMPTION */ |
| 207 | #define preempt_enable() \ |
| 208 | do { \ |
| 209 | barrier(); \ |
| 210 | preempt_count_dec(); \ |
| 211 | } while (0) |
| 212 | |
| 213 | #define preempt_enable_notrace() \ |
| 214 | do { \ |
| 215 | barrier(); \ |
| 216 | __preempt_count_dec(); \ |
| 217 | } while (0) |
| 218 | |
| 219 | #define preempt_check_resched() do { } while (0) |
| 220 | #endif /* CONFIG_PREEMPTION */ |
| 221 | |
| 222 | #define preempt_disable_notrace() \ |
| 223 | do { \ |
| 224 | __preempt_count_inc(); \ |
| 225 | barrier(); \ |
| 226 | } while (0) |
| 227 | |
| 228 | #define preempt_enable_no_resched_notrace() \ |
| 229 | do { \ |
| 230 | barrier(); \ |
| 231 | __preempt_count_dec(); \ |
| 232 | } while (0) |
| 233 | |
| 234 | #else /* !CONFIG_PREEMPT_COUNT */ |
| 235 | |
| 236 | /* |
| 237 | * Even if we don't have any preemption, we need preempt disable/enable |
| 238 | * to be barriers, so that we don't have things like get_user/put_user |
| 239 | * that can cause faults and scheduling migrate into our preempt-protected |
| 240 | * region. |
| 241 | */ |
| 242 | #define preempt_disable() barrier() |
| 243 | #define sched_preempt_enable_no_resched() barrier() |
| 244 | #define preempt_enable_no_resched() barrier() |
| 245 | #define preempt_enable() barrier() |
| 246 | #define preempt_check_resched() do { } while (0) |
| 247 | |
| 248 | #define preempt_disable_notrace() barrier() |
| 249 | #define preempt_enable_no_resched_notrace() barrier() |
| 250 | #define preempt_enable_notrace() barrier() |
| 251 | #define preemptible() 0 |
| 252 | |
| 253 | #endif /* CONFIG_PREEMPT_COUNT */ |
| 254 | |
| 255 | #ifdef MODULE |
| 256 | /* |
| 257 | * Modules have no business playing preemption tricks. |
| 258 | */ |
| 259 | #undef sched_preempt_enable_no_resched |
| 260 | #undef preempt_enable_no_resched |
| 261 | #undef preempt_enable_no_resched_notrace |
| 262 | #undef preempt_check_resched |
| 263 | #endif |
| 264 | |
| 265 | #define preempt_set_need_resched() \ |
| 266 | do { \ |
| 267 | set_preempt_need_resched(); \ |
| 268 | } while (0) |
| 269 | #define preempt_fold_need_resched() \ |
| 270 | do { \ |
| 271 | if (tif_need_resched()) \ |
| 272 | set_preempt_need_resched(); \ |
| 273 | } while (0) |
| 274 | |
| 275 | #ifdef CONFIG_PREEMPT_NOTIFIERS |
| 276 | |
| 277 | struct preempt_notifier; |
| 278 | |
| 279 | /** |
| 280 | * preempt_ops - notifiers called when a task is preempted and rescheduled |
| 281 | * @sched_in: we're about to be rescheduled: |
| 282 | * notifier: struct preempt_notifier for the task being scheduled |
| 283 | * cpu: cpu we're scheduled on |
| 284 | * @sched_out: we've just been preempted |
| 285 | * notifier: struct preempt_notifier for the task being preempted |
| 286 | * next: the task that's kicking us out |
| 287 | * |
| 288 | * Please note that sched_in and out are called under different |
| 289 | * contexts. sched_out is called with rq lock held and irq disabled |
| 290 | * while sched_in is called without rq lock and irq enabled. This |
| 291 | * difference is intentional and depended upon by its users. |
| 292 | */ |
| 293 | struct preempt_ops { |
| 294 | void (*sched_in)(struct preempt_notifier *notifier, int cpu); |
| 295 | void (*sched_out)(struct preempt_notifier *notifier, |
| 296 | struct task_struct *next); |
| 297 | }; |
| 298 | |
| 299 | /** |
| 300 | * preempt_notifier - key for installing preemption notifiers |
| 301 | * @link: internal use |
| 302 | * @ops: defines the notifier functions to be called |
| 303 | * |
| 304 | * Usually used in conjunction with container_of(). |
| 305 | */ |
| 306 | struct preempt_notifier { |
| 307 | struct hlist_node link; |
| 308 | struct preempt_ops *ops; |
| 309 | }; |
| 310 | |
| 311 | void preempt_notifier_inc(void); |
| 312 | void preempt_notifier_dec(void); |
| 313 | void preempt_notifier_register(struct preempt_notifier *notifier); |
| 314 | void preempt_notifier_unregister(struct preempt_notifier *notifier); |
| 315 | |
| 316 | static inline void preempt_notifier_init(struct preempt_notifier *notifier, |
| 317 | struct preempt_ops *ops) |
| 318 | { |
| 319 | INIT_HLIST_NODE(¬ifier->link); |
| 320 | notifier->ops = ops; |
| 321 | } |
| 322 | |
| 323 | #endif |
| 324 | |
| 325 | /** |
| 326 | * migrate_disable - Prevent migration of the current task |
| 327 | * |
| 328 | * Maps to preempt_disable() which also disables preemption. Use |
| 329 | * migrate_disable() to annotate that the intent is to prevent migration, |
| 330 | * but not necessarily preemption. |
| 331 | * |
| 332 | * Can be invoked nested like preempt_disable() and needs the corresponding |
| 333 | * number of migrate_enable() invocations. |
| 334 | */ |
| 335 | static __always_inline void migrate_disable(void) |
| 336 | { |
| 337 | preempt_disable(); |
| 338 | } |
| 339 | |
| 340 | /** |
| 341 | * migrate_enable - Allow migration of the current task |
| 342 | * |
| 343 | * Counterpart to migrate_disable(). |
| 344 | * |
| 345 | * As migrate_disable() can be invoked nested, only the outermost invocation |
| 346 | * reenables migration. |
| 347 | * |
| 348 | * Currently mapped to preempt_enable(). |
| 349 | */ |
| 350 | static __always_inline void migrate_enable(void) |
| 351 | { |
| 352 | preempt_enable(); |
| 353 | } |
| 354 | |
| 355 | #endif /* __LINUX_PREEMPT_H */ |