| 1 | /* |
| 2 | * linux/kernel/softirq.c |
| 3 | * |
| 4 | * Copyright (C) 1992 Linus Torvalds |
| 5 | * |
| 6 | * Distribute under GPLv2. |
| 7 | * |
| 8 | * Rewritten. Old one was good in 2.2, but in 2.3 it was immoral. --ANK (990903) |
| 9 | */ |
| 10 | |
| 11 | #include <linux/export.h> |
| 12 | #include <linux/kernel_stat.h> |
| 13 | #include <linux/interrupt.h> |
| 14 | #include <linux/init.h> |
| 15 | #include <linux/mm.h> |
| 16 | #include <linux/notifier.h> |
| 17 | #include <linux/percpu.h> |
| 18 | #include <linux/cpu.h> |
| 19 | #include <linux/freezer.h> |
| 20 | #include <linux/kthread.h> |
| 21 | #include <linux/rcupdate.h> |
| 22 | #include <linux/ftrace.h> |
| 23 | #include <linux/smp.h> |
| 24 | #include <linux/smpboot.h> |
| 25 | #include <linux/tick.h> |
| 26 | |
| 27 | #include <linux/mt_sched_mon.h> |
| 28 | #define CREATE_TRACE_POINTS |
| 29 | #include <trace/events/irq.h> |
| 30 | |
| 31 | #include <asm/irq.h> |
| 32 | /* |
| 33 | - No shared variables, all the data are CPU local. |
| 34 | - If a softirq needs serialization, let it serialize itself |
| 35 | by its own spinlocks. |
| 36 | - Even if softirq is serialized, only local cpu is marked for |
| 37 | execution. Hence, we get something sort of weak cpu binding. |
| 38 | Though it is still not clear, will it result in better locality |
| 39 | or will not. |
| 40 | |
| 41 | Examples: |
| 42 | - NET RX softirq. It is multithreaded and does not require |
| 43 | any global serialization. |
| 44 | - NET TX softirq. It kicks software netdevice queues, hence |
| 45 | it is logically serialized per device, but this serialization |
| 46 | is invisible to common code. |
| 47 | - Tasklets: serialized wrt itself. |
| 48 | */ |
| 49 | |
| 50 | #ifndef __ARCH_IRQ_STAT |
| 51 | irq_cpustat_t irq_stat[NR_CPUS] ____cacheline_aligned; |
| 52 | EXPORT_SYMBOL(irq_stat); |
| 53 | #endif |
| 54 | |
| 55 | static struct softirq_action softirq_vec[NR_SOFTIRQS] __cacheline_aligned_in_smp; |
| 56 | |
| 57 | DEFINE_PER_CPU(struct task_struct *, ksoftirqd); |
| 58 | |
| 59 | char *softirq_to_name[NR_SOFTIRQS] = { |
| 60 | "HI", "TIMER", "NET_TX", "NET_RX", "BLOCK", "BLOCK_IOPOLL", |
| 61 | "TASKLET", "SCHED", "HRTIMER", "RCU" |
| 62 | }; |
| 63 | |
| 64 | /* |
| 65 | * we cannot loop indefinitely here to avoid userspace starvation, |
| 66 | * but we also don't want to introduce a worst case 1/HZ latency |
| 67 | * to the pending events, so lets the scheduler to balance |
| 68 | * the softirq load for us. |
| 69 | */ |
| 70 | static void wakeup_softirqd(void) |
| 71 | { |
| 72 | /* Interrupts are disabled: no need to stop preemption */ |
| 73 | struct task_struct *tsk = __this_cpu_read(ksoftirqd); |
| 74 | |
| 75 | if (tsk && tsk->state != TASK_RUNNING) |
| 76 | wake_up_process(tsk); |
| 77 | } |
| 78 | |
| 79 | /* |
| 80 | * preempt_count and SOFTIRQ_OFFSET usage: |
| 81 | * - preempt_count is changed by SOFTIRQ_OFFSET on entering or leaving |
| 82 | * softirq processing. |
| 83 | * - preempt_count is changed by SOFTIRQ_DISABLE_OFFSET (= 2 * SOFTIRQ_OFFSET) |
| 84 | * on local_bh_disable or local_bh_enable. |
| 85 | * This lets us distinguish between whether we are currently processing |
| 86 | * softirq and whether we just have bh disabled. |
| 87 | */ |
| 88 | |
| 89 | /* |
| 90 | * This one is for softirq.c-internal use, |
| 91 | * where hardirqs are disabled legitimately: |
| 92 | */ |
| 93 | #ifdef CONFIG_TRACE_IRQFLAGS |
| 94 | static void __local_bh_disable(unsigned long ip, unsigned int cnt) |
| 95 | { |
| 96 | unsigned long flags; |
| 97 | |
| 98 | WARN_ON_ONCE(in_irq()); |
| 99 | |
| 100 | raw_local_irq_save(flags); |
| 101 | /* |
| 102 | * The preempt tracer hooks into add_preempt_count and will break |
| 103 | * lockdep because it calls back into lockdep after SOFTIRQ_OFFSET |
| 104 | * is set and before current->softirq_enabled is cleared. |
| 105 | * We must manually increment preempt_count here and manually |
| 106 | * call the trace_preempt_off later. |
| 107 | */ |
| 108 | preempt_count() += cnt; |
| 109 | /* |
| 110 | * Were softirqs turned off above: |
| 111 | */ |
| 112 | if (softirq_count() == cnt) |
| 113 | trace_softirqs_off(ip); |
| 114 | raw_local_irq_restore(flags); |
| 115 | |
| 116 | if (preempt_count() == cnt) |
| 117 | trace_preempt_off(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1)); |
| 118 | } |
| 119 | #else /* !CONFIG_TRACE_IRQFLAGS */ |
| 120 | static inline void __local_bh_disable(unsigned long ip, unsigned int cnt) |
| 121 | { |
| 122 | add_preempt_count(cnt); |
| 123 | barrier(); |
| 124 | } |
| 125 | #endif /* CONFIG_TRACE_IRQFLAGS */ |
| 126 | |
| 127 | void local_bh_disable(void) |
| 128 | { |
| 129 | __local_bh_disable((unsigned long)__builtin_return_address(0), |
| 130 | SOFTIRQ_DISABLE_OFFSET); |
| 131 | } |
| 132 | |
| 133 | EXPORT_SYMBOL(local_bh_disable); |
| 134 | |
| 135 | static void __local_bh_enable(unsigned int cnt) |
| 136 | { |
| 137 | WARN_ON_ONCE(in_irq()); |
| 138 | WARN_ON_ONCE(!irqs_disabled()); |
| 139 | |
| 140 | if (softirq_count() == cnt) |
| 141 | trace_softirqs_on((unsigned long)__builtin_return_address(0)); |
| 142 | sub_preempt_count(cnt); |
| 143 | } |
| 144 | |
| 145 | /* |
| 146 | * Special-case - softirqs can safely be enabled in |
| 147 | * cond_resched_softirq(), or by __do_softirq(), |
| 148 | * without processing still-pending softirqs: |
| 149 | */ |
| 150 | void _local_bh_enable(void) |
| 151 | { |
| 152 | __local_bh_enable(SOFTIRQ_DISABLE_OFFSET); |
| 153 | } |
| 154 | |
| 155 | EXPORT_SYMBOL(_local_bh_enable); |
| 156 | |
| 157 | static inline void _local_bh_enable_ip(unsigned long ip) |
| 158 | { |
| 159 | WARN_ON_ONCE(in_irq() || irqs_disabled()); |
| 160 | #ifdef CONFIG_TRACE_IRQFLAGS |
| 161 | local_irq_disable(); |
| 162 | #endif |
| 163 | /* |
| 164 | * Are softirqs going to be turned on now: |
| 165 | */ |
| 166 | if (softirq_count() == SOFTIRQ_DISABLE_OFFSET) |
| 167 | trace_softirqs_on(ip); |
| 168 | /* |
| 169 | * Keep preemption disabled until we are done with |
| 170 | * softirq processing: |
| 171 | */ |
| 172 | sub_preempt_count(SOFTIRQ_DISABLE_OFFSET - 1); |
| 173 | |
| 174 | if (unlikely(!in_interrupt() && local_softirq_pending())) |
| 175 | do_softirq(); |
| 176 | |
| 177 | dec_preempt_count(); |
| 178 | #ifdef CONFIG_TRACE_IRQFLAGS |
| 179 | local_irq_enable(); |
| 180 | #endif |
| 181 | preempt_check_resched(); |
| 182 | } |
| 183 | |
| 184 | void local_bh_enable(void) |
| 185 | { |
| 186 | _local_bh_enable_ip((unsigned long)__builtin_return_address(0)); |
| 187 | } |
| 188 | EXPORT_SYMBOL(local_bh_enable); |
| 189 | |
| 190 | void local_bh_enable_ip(unsigned long ip) |
| 191 | { |
| 192 | _local_bh_enable_ip(ip); |
| 193 | } |
| 194 | EXPORT_SYMBOL(local_bh_enable_ip); |
| 195 | |
| 196 | /* |
| 197 | * We restart softirq processing for at most MAX_SOFTIRQ_RESTART times, |
| 198 | * but break the loop if need_resched() is set or after 2 ms. |
| 199 | * The MAX_SOFTIRQ_TIME provides a nice upper bound in most cases, but in |
| 200 | * certain cases, such as stop_machine(), jiffies may cease to |
| 201 | * increment and so we need the MAX_SOFTIRQ_RESTART limit as |
| 202 | * well to make sure we eventually return from this method. |
| 203 | * |
| 204 | * These limits have been established via experimentation. |
| 205 | * The two things to balance is latency against fairness - |
| 206 | * we want to handle softirqs as soon as possible, but they |
| 207 | * should not be able to lock up the box. |
| 208 | */ |
| 209 | #define MAX_SOFTIRQ_TIME msecs_to_jiffies(2) |
| 210 | #define MAX_SOFTIRQ_RESTART 10 |
| 211 | |
| 212 | asmlinkage void __do_softirq(void) |
| 213 | { |
| 214 | struct softirq_action *h; |
| 215 | __u32 pending; |
| 216 | unsigned long end = jiffies + MAX_SOFTIRQ_TIME; |
| 217 | int cpu; |
| 218 | unsigned long old_flags = current->flags; |
| 219 | int max_restart = MAX_SOFTIRQ_RESTART; |
| 220 | |
| 221 | /* |
| 222 | * Mask out PF_MEMALLOC s current task context is borrowed for the |
| 223 | * softirq. A softirq handled such as network RX might set PF_MEMALLOC |
| 224 | * again if the socket is related to swap |
| 225 | */ |
| 226 | current->flags &= ~PF_MEMALLOC; |
| 227 | |
| 228 | pending = local_softirq_pending(); |
| 229 | account_irq_enter_time(current); |
| 230 | |
| 231 | __local_bh_disable((unsigned long)__builtin_return_address(0), |
| 232 | SOFTIRQ_OFFSET); |
| 233 | lockdep_softirq_enter(); |
| 234 | |
| 235 | cpu = smp_processor_id(); |
| 236 | restart: |
| 237 | /* Reset the pending bitmask before enabling irqs */ |
| 238 | set_softirq_pending(0); |
| 239 | |
| 240 | local_irq_enable(); |
| 241 | |
| 242 | h = softirq_vec; |
| 243 | |
| 244 | do { |
| 245 | if (pending & 1) { |
| 246 | unsigned int vec_nr = h - softirq_vec; |
| 247 | int prev_count = preempt_count(); |
| 248 | |
| 249 | kstat_incr_softirqs_this_cpu(vec_nr); |
| 250 | |
| 251 | trace_softirq_entry(vec_nr); |
| 252 | mt_trace_SoftIRQ_start(vec_nr); |
| 253 | h->action(h); |
| 254 | mt_trace_SoftIRQ_end(vec_nr); |
| 255 | trace_softirq_exit(vec_nr); |
| 256 | if (unlikely(prev_count != preempt_count())) { |
| 257 | printk(KERN_ERR "huh, entered softirq %u %s %p" |
| 258 | "with preempt_count %08x," |
| 259 | " exited with %08x?\n", vec_nr, |
| 260 | softirq_to_name[vec_nr], h->action, |
| 261 | prev_count, preempt_count()); |
| 262 | preempt_count() = prev_count; |
| 263 | } |
| 264 | |
| 265 | rcu_bh_qs(cpu); |
| 266 | } |
| 267 | h++; |
| 268 | pending >>= 1; |
| 269 | } while (pending); |
| 270 | |
| 271 | local_irq_disable(); |
| 272 | |
| 273 | pending = local_softirq_pending(); |
| 274 | if (pending) { |
| 275 | if (time_before(jiffies, end) && !need_resched() && |
| 276 | --max_restart) |
| 277 | goto restart; |
| 278 | |
| 279 | wakeup_softirqd(); |
| 280 | } |
| 281 | |
| 282 | lockdep_softirq_exit(); |
| 283 | |
| 284 | account_irq_exit_time(current); |
| 285 | __local_bh_enable(SOFTIRQ_OFFSET); |
| 286 | tsk_restore_flags(current, old_flags, PF_MEMALLOC); |
| 287 | } |
| 288 | |
| 289 | #ifndef __ARCH_HAS_DO_SOFTIRQ |
| 290 | |
| 291 | asmlinkage void do_softirq(void) |
| 292 | { |
| 293 | __u32 pending; |
| 294 | unsigned long flags; |
| 295 | |
| 296 | if (in_interrupt()) |
| 297 | return; |
| 298 | |
| 299 | local_irq_save(flags); |
| 300 | |
| 301 | pending = local_softirq_pending(); |
| 302 | |
| 303 | if (pending) |
| 304 | __do_softirq(); |
| 305 | |
| 306 | local_irq_restore(flags); |
| 307 | } |
| 308 | |
| 309 | #endif |
| 310 | |
| 311 | /* |
| 312 | * Enter an interrupt context. |
| 313 | */ |
| 314 | void irq_enter(void) |
| 315 | { |
| 316 | int cpu = smp_processor_id(); |
| 317 | |
| 318 | rcu_irq_enter(); |
| 319 | if (is_idle_task(current) && !in_interrupt()) { |
| 320 | /* |
| 321 | * Prevent raise_softirq from needlessly waking up ksoftirqd |
| 322 | * here, as softirq will be serviced on return from interrupt. |
| 323 | */ |
| 324 | local_bh_disable(); |
| 325 | tick_check_idle(cpu); |
| 326 | _local_bh_enable(); |
| 327 | } |
| 328 | |
| 329 | __irq_enter(); |
| 330 | } |
| 331 | |
| 332 | static inline void invoke_softirq(void) |
| 333 | { |
| 334 | if (!force_irqthreads) { |
| 335 | /* |
| 336 | * We can safely execute softirq on the current stack if |
| 337 | * it is the irq stack, because it should be near empty |
| 338 | * at this stage. But we have no way to know if the arch |
| 339 | * calls irq_exit() on the irq stack. So call softirq |
| 340 | * in its own stack to prevent from any overrun on top |
| 341 | * of a potentially deep task stack. |
| 342 | */ |
| 343 | do_softirq(); |
| 344 | } else { |
| 345 | wakeup_softirqd(); |
| 346 | } |
| 347 | } |
| 348 | |
| 349 | static inline void tick_irq_exit(void) |
| 350 | { |
| 351 | #ifdef CONFIG_NO_HZ_COMMON |
| 352 | int cpu = smp_processor_id(); |
| 353 | |
| 354 | /* Make sure that timer wheel updates are propagated */ |
| 355 | if ((idle_cpu(cpu) && !need_resched()) || tick_nohz_full_cpu(cpu)) { |
| 356 | if (!in_interrupt()) |
| 357 | tick_nohz_irq_exit(); |
| 358 | } |
| 359 | #endif |
| 360 | } |
| 361 | |
| 362 | /* |
| 363 | * Exit an interrupt context. Process softirqs if needed and possible: |
| 364 | */ |
| 365 | void irq_exit(void) |
| 366 | { |
| 367 | #ifndef __ARCH_IRQ_EXIT_IRQS_DISABLED |
| 368 | local_irq_disable(); |
| 369 | #else |
| 370 | WARN_ON_ONCE(!irqs_disabled()); |
| 371 | #endif |
| 372 | |
| 373 | account_irq_exit_time(current); |
| 374 | trace_hardirq_exit(); |
| 375 | sub_preempt_count(HARDIRQ_OFFSET); |
| 376 | if (!in_interrupt() && local_softirq_pending()) |
| 377 | invoke_softirq(); |
| 378 | |
| 379 | tick_irq_exit(); |
| 380 | rcu_irq_exit(); |
| 381 | } |
| 382 | |
| 383 | /* |
| 384 | * This function must run with irqs disabled! |
| 385 | */ |
| 386 | inline void raise_softirq_irqoff(unsigned int nr) |
| 387 | { |
| 388 | __raise_softirq_irqoff(nr); |
| 389 | |
| 390 | /* |
| 391 | * If we're in an interrupt or softirq, we're done |
| 392 | * (this also catches softirq-disabled code). We will |
| 393 | * actually run the softirq once we return from |
| 394 | * the irq or softirq. |
| 395 | * |
| 396 | * Otherwise we wake up ksoftirqd to make sure we |
| 397 | * schedule the softirq soon. |
| 398 | */ |
| 399 | if (!in_interrupt()) |
| 400 | wakeup_softirqd(); |
| 401 | } |
| 402 | |
| 403 | void raise_softirq(unsigned int nr) |
| 404 | { |
| 405 | unsigned long flags; |
| 406 | |
| 407 | local_irq_save(flags); |
| 408 | raise_softirq_irqoff(nr); |
| 409 | local_irq_restore(flags); |
| 410 | } |
| 411 | |
| 412 | void __raise_softirq_irqoff(unsigned int nr) |
| 413 | { |
| 414 | trace_softirq_raise(nr); |
| 415 | or_softirq_pending(1UL << nr); |
| 416 | } |
| 417 | |
| 418 | void open_softirq(int nr, void (*action)(struct softirq_action *)) |
| 419 | { |
| 420 | softirq_vec[nr].action = action; |
| 421 | } |
| 422 | |
| 423 | /* |
| 424 | * Tasklets |
| 425 | */ |
| 426 | struct tasklet_head |
| 427 | { |
| 428 | struct tasklet_struct *head; |
| 429 | struct tasklet_struct **tail; |
| 430 | }; |
| 431 | |
| 432 | static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec); |
| 433 | static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec); |
| 434 | |
| 435 | void __tasklet_schedule(struct tasklet_struct *t) |
| 436 | { |
| 437 | unsigned long flags; |
| 438 | |
| 439 | local_irq_save(flags); |
| 440 | t->next = NULL; |
| 441 | *__this_cpu_read(tasklet_vec.tail) = t; |
| 442 | __this_cpu_write(tasklet_vec.tail, &(t->next)); |
| 443 | raise_softirq_irqoff(TASKLET_SOFTIRQ); |
| 444 | local_irq_restore(flags); |
| 445 | } |
| 446 | |
| 447 | EXPORT_SYMBOL(__tasklet_schedule); |
| 448 | |
| 449 | void __tasklet_hi_schedule(struct tasklet_struct *t) |
| 450 | { |
| 451 | unsigned long flags; |
| 452 | |
| 453 | local_irq_save(flags); |
| 454 | t->next = NULL; |
| 455 | *__this_cpu_read(tasklet_hi_vec.tail) = t; |
| 456 | __this_cpu_write(tasklet_hi_vec.tail, &(t->next)); |
| 457 | raise_softirq_irqoff(HI_SOFTIRQ); |
| 458 | local_irq_restore(flags); |
| 459 | } |
| 460 | |
| 461 | EXPORT_SYMBOL(__tasklet_hi_schedule); |
| 462 | |
| 463 | void __tasklet_hi_schedule_first(struct tasklet_struct *t) |
| 464 | { |
| 465 | BUG_ON(!irqs_disabled()); |
| 466 | |
| 467 | t->next = __this_cpu_read(tasklet_hi_vec.head); |
| 468 | __this_cpu_write(tasklet_hi_vec.head, t); |
| 469 | __raise_softirq_irqoff(HI_SOFTIRQ); |
| 470 | } |
| 471 | |
| 472 | EXPORT_SYMBOL(__tasklet_hi_schedule_first); |
| 473 | |
| 474 | static void tasklet_action(struct softirq_action *a) |
| 475 | { |
| 476 | struct tasklet_struct *list; |
| 477 | |
| 478 | local_irq_disable(); |
| 479 | list = __this_cpu_read(tasklet_vec.head); |
| 480 | __this_cpu_write(tasklet_vec.head, NULL); |
| 481 | __this_cpu_write(tasklet_vec.tail, &__get_cpu_var(tasklet_vec).head); |
| 482 | local_irq_enable(); |
| 483 | |
| 484 | while (list) { |
| 485 | struct tasklet_struct *t = list; |
| 486 | |
| 487 | list = list->next; |
| 488 | |
| 489 | if (tasklet_trylock(t)) { |
| 490 | if (!atomic_read(&t->count)) { |
| 491 | if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state)) |
| 492 | BUG(); |
| 493 | mt_trace_tasklet_start(t->func); |
| 494 | t->func(t->data); |
| 495 | mt_trace_tasklet_end(t->func); |
| 496 | tasklet_unlock(t); |
| 497 | continue; |
| 498 | } |
| 499 | tasklet_unlock(t); |
| 500 | } |
| 501 | |
| 502 | local_irq_disable(); |
| 503 | t->next = NULL; |
| 504 | *__this_cpu_read(tasklet_vec.tail) = t; |
| 505 | __this_cpu_write(tasklet_vec.tail, &(t->next)); |
| 506 | __raise_softirq_irqoff(TASKLET_SOFTIRQ); |
| 507 | local_irq_enable(); |
| 508 | } |
| 509 | } |
| 510 | |
| 511 | static void tasklet_hi_action(struct softirq_action *a) |
| 512 | { |
| 513 | struct tasklet_struct *list; |
| 514 | |
| 515 | local_irq_disable(); |
| 516 | list = __this_cpu_read(tasklet_hi_vec.head); |
| 517 | __this_cpu_write(tasklet_hi_vec.head, NULL); |
| 518 | __this_cpu_write(tasklet_hi_vec.tail, &__get_cpu_var(tasklet_hi_vec).head); |
| 519 | local_irq_enable(); |
| 520 | |
| 521 | while (list) { |
| 522 | struct tasklet_struct *t = list; |
| 523 | |
| 524 | list = list->next; |
| 525 | |
| 526 | if (tasklet_trylock(t)) { |
| 527 | if (!atomic_read(&t->count)) { |
| 528 | if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state)) |
| 529 | BUG(); |
| 530 | t->func(t->data); |
| 531 | tasklet_unlock(t); |
| 532 | continue; |
| 533 | } |
| 534 | tasklet_unlock(t); |
| 535 | } |
| 536 | |
| 537 | local_irq_disable(); |
| 538 | t->next = NULL; |
| 539 | *__this_cpu_read(tasklet_hi_vec.tail) = t; |
| 540 | __this_cpu_write(tasklet_hi_vec.tail, &(t->next)); |
| 541 | __raise_softirq_irqoff(HI_SOFTIRQ); |
| 542 | local_irq_enable(); |
| 543 | } |
| 544 | } |
| 545 | |
| 546 | |
| 547 | void tasklet_init(struct tasklet_struct *t, |
| 548 | void (*func)(unsigned long), unsigned long data) |
| 549 | { |
| 550 | t->next = NULL; |
| 551 | t->state = 0; |
| 552 | atomic_set(&t->count, 0); |
| 553 | t->func = func; |
| 554 | t->data = data; |
| 555 | } |
| 556 | |
| 557 | EXPORT_SYMBOL(tasklet_init); |
| 558 | |
| 559 | void tasklet_kill(struct tasklet_struct *t) |
| 560 | { |
| 561 | if (in_interrupt()) |
| 562 | printk("Attempt to kill tasklet from interrupt\n"); |
| 563 | |
| 564 | while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) { |
| 565 | do { |
| 566 | yield(); |
| 567 | } while (test_bit(TASKLET_STATE_SCHED, &t->state)); |
| 568 | } |
| 569 | tasklet_unlock_wait(t); |
| 570 | clear_bit(TASKLET_STATE_SCHED, &t->state); |
| 571 | } |
| 572 | |
| 573 | EXPORT_SYMBOL(tasklet_kill); |
| 574 | |
| 575 | /* |
| 576 | * tasklet_hrtimer |
| 577 | */ |
| 578 | |
| 579 | /* |
| 580 | * The trampoline is called when the hrtimer expires. It schedules a tasklet |
| 581 | * to run __tasklet_hrtimer_trampoline() which in turn will call the intended |
| 582 | * hrtimer callback, but from softirq context. |
| 583 | */ |
| 584 | static enum hrtimer_restart __hrtimer_tasklet_trampoline(struct hrtimer *timer) |
| 585 | { |
| 586 | struct tasklet_hrtimer *ttimer = |
| 587 | container_of(timer, struct tasklet_hrtimer, timer); |
| 588 | |
| 589 | tasklet_hi_schedule(&ttimer->tasklet); |
| 590 | return HRTIMER_NORESTART; |
| 591 | } |
| 592 | |
| 593 | /* |
| 594 | * Helper function which calls the hrtimer callback from |
| 595 | * tasklet/softirq context |
| 596 | */ |
| 597 | static void __tasklet_hrtimer_trampoline(unsigned long data) |
| 598 | { |
| 599 | struct tasklet_hrtimer *ttimer = (void *)data; |
| 600 | enum hrtimer_restart restart; |
| 601 | |
| 602 | restart = ttimer->function(&ttimer->timer); |
| 603 | if (restart != HRTIMER_NORESTART) |
| 604 | hrtimer_restart(&ttimer->timer); |
| 605 | } |
| 606 | |
| 607 | /** |
| 608 | * tasklet_hrtimer_init - Init a tasklet/hrtimer combo for softirq callbacks |
| 609 | * @ttimer: tasklet_hrtimer which is initialized |
| 610 | * @function: hrtimer callback function which gets called from softirq context |
| 611 | * @which_clock: clock id (CLOCK_MONOTONIC/CLOCK_REALTIME) |
| 612 | * @mode: hrtimer mode (HRTIMER_MODE_ABS/HRTIMER_MODE_REL) |
| 613 | */ |
| 614 | void tasklet_hrtimer_init(struct tasklet_hrtimer *ttimer, |
| 615 | enum hrtimer_restart (*function)(struct hrtimer *), |
| 616 | clockid_t which_clock, enum hrtimer_mode mode) |
| 617 | { |
| 618 | hrtimer_init(&ttimer->timer, which_clock, mode); |
| 619 | ttimer->timer.function = __hrtimer_tasklet_trampoline; |
| 620 | tasklet_init(&ttimer->tasklet, __tasklet_hrtimer_trampoline, |
| 621 | (unsigned long)ttimer); |
| 622 | ttimer->function = function; |
| 623 | } |
| 624 | EXPORT_SYMBOL_GPL(tasklet_hrtimer_init); |
| 625 | |
| 626 | void __init softirq_init(void) |
| 627 | { |
| 628 | int cpu; |
| 629 | |
| 630 | for_each_possible_cpu(cpu) { |
| 631 | per_cpu(tasklet_vec, cpu).tail = |
| 632 | &per_cpu(tasklet_vec, cpu).head; |
| 633 | per_cpu(tasklet_hi_vec, cpu).tail = |
| 634 | &per_cpu(tasklet_hi_vec, cpu).head; |
| 635 | } |
| 636 | |
| 637 | open_softirq(TASKLET_SOFTIRQ, tasklet_action); |
| 638 | open_softirq(HI_SOFTIRQ, tasklet_hi_action); |
| 639 | } |
| 640 | |
| 641 | static int ksoftirqd_should_run(unsigned int cpu) |
| 642 | { |
| 643 | return local_softirq_pending(); |
| 644 | } |
| 645 | |
| 646 | static void run_ksoftirqd(unsigned int cpu) |
| 647 | { |
| 648 | local_irq_disable(); |
| 649 | if (local_softirq_pending()) { |
| 650 | __do_softirq(); |
| 651 | local_irq_enable(); |
| 652 | cond_resched(); |
| 653 | |
| 654 | preempt_disable(); |
| 655 | rcu_note_context_switch(cpu); |
| 656 | preempt_enable(); |
| 657 | |
| 658 | return; |
| 659 | } |
| 660 | local_irq_enable(); |
| 661 | } |
| 662 | |
| 663 | #ifdef CONFIG_HOTPLUG_CPU |
| 664 | /* |
| 665 | * tasklet_kill_immediate is called to remove a tasklet which can already be |
| 666 | * scheduled for execution on @cpu. |
| 667 | * |
| 668 | * Unlike tasklet_kill, this function removes the tasklet |
| 669 | * _immediately_, even if the tasklet is in TASKLET_STATE_SCHED state. |
| 670 | * |
| 671 | * When this function is called, @cpu must be in the CPU_DEAD state. |
| 672 | */ |
| 673 | void tasklet_kill_immediate(struct tasklet_struct *t, unsigned int cpu) |
| 674 | { |
| 675 | struct tasklet_struct **i; |
| 676 | |
| 677 | BUG_ON(cpu_online(cpu)); |
| 678 | BUG_ON(test_bit(TASKLET_STATE_RUN, &t->state)); |
| 679 | |
| 680 | if (!test_bit(TASKLET_STATE_SCHED, &t->state)) |
| 681 | return; |
| 682 | |
| 683 | /* CPU is dead, so no lock needed. */ |
| 684 | for (i = &per_cpu(tasklet_vec, cpu).head; *i; i = &(*i)->next) { |
| 685 | if (*i == t) { |
| 686 | *i = t->next; |
| 687 | /* If this was the tail element, move the tail ptr */ |
| 688 | if (*i == NULL) |
| 689 | per_cpu(tasklet_vec, cpu).tail = i; |
| 690 | return; |
| 691 | } |
| 692 | } |
| 693 | BUG(); |
| 694 | } |
| 695 | |
| 696 | static void takeover_tasklets(unsigned int cpu) |
| 697 | { |
| 698 | /* CPU is dead, so no lock needed. */ |
| 699 | local_irq_disable(); |
| 700 | |
| 701 | /* Find end, append list for that CPU. */ |
| 702 | if (&per_cpu(tasklet_vec, cpu).head != per_cpu(tasklet_vec, cpu).tail) { |
| 703 | *__this_cpu_read(tasklet_vec.tail) = per_cpu(tasklet_vec, cpu).head; |
| 704 | this_cpu_write(tasklet_vec.tail, per_cpu(tasklet_vec, cpu).tail); |
| 705 | per_cpu(tasklet_vec, cpu).head = NULL; |
| 706 | per_cpu(tasklet_vec, cpu).tail = &per_cpu(tasklet_vec, cpu).head; |
| 707 | } |
| 708 | raise_softirq_irqoff(TASKLET_SOFTIRQ); |
| 709 | |
| 710 | if (&per_cpu(tasklet_hi_vec, cpu).head != per_cpu(tasklet_hi_vec, cpu).tail) { |
| 711 | *__this_cpu_read(tasklet_hi_vec.tail) = per_cpu(tasklet_hi_vec, cpu).head; |
| 712 | __this_cpu_write(tasklet_hi_vec.tail, per_cpu(tasklet_hi_vec, cpu).tail); |
| 713 | per_cpu(tasklet_hi_vec, cpu).head = NULL; |
| 714 | per_cpu(tasklet_hi_vec, cpu).tail = &per_cpu(tasklet_hi_vec, cpu).head; |
| 715 | } |
| 716 | raise_softirq_irqoff(HI_SOFTIRQ); |
| 717 | |
| 718 | local_irq_enable(); |
| 719 | } |
| 720 | #endif /* CONFIG_HOTPLUG_CPU */ |
| 721 | |
| 722 | static int __cpuinit cpu_callback(struct notifier_block *nfb, |
| 723 | unsigned long action, |
| 724 | void *hcpu) |
| 725 | { |
| 726 | switch (action) { |
| 727 | #ifdef CONFIG_HOTPLUG_CPU |
| 728 | case CPU_DEAD: |
| 729 | case CPU_DEAD_FROZEN: |
| 730 | takeover_tasklets((unsigned long)hcpu); |
| 731 | break; |
| 732 | #endif /* CONFIG_HOTPLUG_CPU */ |
| 733 | } |
| 734 | return NOTIFY_OK; |
| 735 | } |
| 736 | |
| 737 | static struct notifier_block __cpuinitdata cpu_nfb = { |
| 738 | .notifier_call = cpu_callback |
| 739 | }; |
| 740 | |
| 741 | static struct smp_hotplug_thread softirq_threads = { |
| 742 | .store = &ksoftirqd, |
| 743 | .thread_should_run = ksoftirqd_should_run, |
| 744 | .thread_fn = run_ksoftirqd, |
| 745 | .thread_comm = "ksoftirqd/%u", |
| 746 | }; |
| 747 | |
| 748 | static __init int spawn_ksoftirqd(void) |
| 749 | { |
| 750 | register_cpu_notifier(&cpu_nfb); |
| 751 | |
| 752 | BUG_ON(smpboot_register_percpu_thread(&softirq_threads)); |
| 753 | |
| 754 | return 0; |
| 755 | } |
| 756 | early_initcall(spawn_ksoftirqd); |
| 757 | |
| 758 | /* |
| 759 | * [ These __weak aliases are kept in a separate compilation unit, so that |
| 760 | * GCC does not inline them incorrectly. ] |
| 761 | */ |
| 762 | |
| 763 | int __init __weak early_irq_init(void) |
| 764 | { |
| 765 | return 0; |
| 766 | } |
| 767 | |
| 768 | #ifdef CONFIG_GENERIC_HARDIRQS |
| 769 | int __init __weak arch_probe_nr_irqs(void) |
| 770 | { |
| 771 | return NR_IRQS_LEGACY; |
| 772 | } |
| 773 | |
| 774 | int __init __weak arch_early_irq_init(void) |
| 775 | { |
| 776 | return 0; |
| 777 | } |
| 778 | #endif |