| 1 | // SPDX-License-Identifier: GPL-2.0-only |
| 2 | /* |
| 3 | * linux/kernel/softirq.c |
| 4 | * |
| 5 | * Copyright (C) 1992 Linus Torvalds |
| 6 | * |
| 7 | * Rewritten. Old one was good in 2.2, but in 2.3 it was immoral. --ANK (990903) |
| 8 | */ |
| 9 | |
| 10 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
| 11 | |
| 12 | #include <linux/export.h> |
| 13 | #include <linux/kernel_stat.h> |
| 14 | #include <linux/interrupt.h> |
| 15 | #include <linux/init.h> |
| 16 | #include <linux/local_lock.h> |
| 17 | #include <linux/mm.h> |
| 18 | #include <linux/notifier.h> |
| 19 | #include <linux/percpu.h> |
| 20 | #include <linux/cpu.h> |
| 21 | #include <linux/freezer.h> |
| 22 | #include <linux/kthread.h> |
| 23 | #include <linux/rcupdate.h> |
| 24 | #include <linux/ftrace.h> |
| 25 | #include <linux/smp.h> |
| 26 | #include <linux/smpboot.h> |
| 27 | #include <linux/tick.h> |
| 28 | #include <linux/irq.h> |
| 29 | #include <linux/wait_bit.h> |
| 30 | |
| 31 | #include <asm/softirq_stack.h> |
| 32 | |
| 33 | #define CREATE_TRACE_POINTS |
| 34 | #include <trace/events/irq.h> |
| 35 | |
| 36 | /* |
| 37 | - No shared variables, all the data are CPU local. |
| 38 | - If a softirq needs serialization, let it serialize itself |
| 39 | by its own spinlocks. |
| 40 | - Even if softirq is serialized, only local cpu is marked for |
| 41 | execution. Hence, we get something sort of weak cpu binding. |
| 42 | Though it is still not clear, will it result in better locality |
| 43 | or will not. |
| 44 | |
| 45 | Examples: |
| 46 | - NET RX softirq. It is multithreaded and does not require |
| 47 | any global serialization. |
| 48 | - NET TX softirq. It kicks software netdevice queues, hence |
| 49 | it is logically serialized per device, but this serialization |
| 50 | is invisible to common code. |
| 51 | - Tasklets: serialized wrt itself. |
| 52 | */ |
| 53 | |
| 54 | #ifndef __ARCH_IRQ_STAT |
| 55 | DEFINE_PER_CPU_ALIGNED(irq_cpustat_t, irq_stat); |
| 56 | EXPORT_PER_CPU_SYMBOL(irq_stat); |
| 57 | #endif |
| 58 | |
| 59 | static struct softirq_action softirq_vec[NR_SOFTIRQS] __cacheline_aligned_in_smp; |
| 60 | |
| 61 | DEFINE_PER_CPU(struct task_struct *, ksoftirqd); |
| 62 | |
| 63 | const char * const softirq_to_name[NR_SOFTIRQS] = { |
| 64 | "HI", "TIMER", "NET_TX", "NET_RX", "BLOCK", "IRQ_POLL", |
| 65 | "TASKLET", "SCHED", "HRTIMER", "RCU" |
| 66 | }; |
| 67 | |
| 68 | /* |
| 69 | * we cannot loop indefinitely here to avoid userspace starvation, |
| 70 | * but we also don't want to introduce a worst case 1/HZ latency |
| 71 | * to the pending events, so lets the scheduler to balance |
| 72 | * the softirq load for us. |
| 73 | */ |
| 74 | static void wakeup_softirqd(void) |
| 75 | { |
| 76 | /* Interrupts are disabled: no need to stop preemption */ |
| 77 | struct task_struct *tsk = __this_cpu_read(ksoftirqd); |
| 78 | |
| 79 | if (tsk) |
| 80 | wake_up_process(tsk); |
| 81 | } |
| 82 | |
| 83 | /* |
| 84 | * If ksoftirqd is scheduled, we do not want to process pending softirqs |
| 85 | * right now. Let ksoftirqd handle this at its own rate, to get fairness, |
| 86 | * unless we're doing some of the synchronous softirqs. |
| 87 | */ |
| 88 | #define SOFTIRQ_NOW_MASK ((1 << HI_SOFTIRQ) | (1 << TASKLET_SOFTIRQ)) |
| 89 | static bool ksoftirqd_running(unsigned long pending) |
| 90 | { |
| 91 | struct task_struct *tsk = __this_cpu_read(ksoftirqd); |
| 92 | |
| 93 | if (pending & SOFTIRQ_NOW_MASK) |
| 94 | return false; |
| 95 | return tsk && task_is_running(tsk) && !__kthread_should_park(tsk); |
| 96 | } |
| 97 | |
| 98 | #ifdef CONFIG_TRACE_IRQFLAGS |
| 99 | DEFINE_PER_CPU(int, hardirqs_enabled); |
| 100 | DEFINE_PER_CPU(int, hardirq_context); |
| 101 | EXPORT_PER_CPU_SYMBOL_GPL(hardirqs_enabled); |
| 102 | EXPORT_PER_CPU_SYMBOL_GPL(hardirq_context); |
| 103 | #endif |
| 104 | |
| 105 | /* |
| 106 | * SOFTIRQ_OFFSET usage: |
| 107 | * |
| 108 | * On !RT kernels 'count' is the preempt counter, on RT kernels this applies |
| 109 | * to a per CPU counter and to task::softirqs_disabled_cnt. |
| 110 | * |
| 111 | * - count is changed by SOFTIRQ_OFFSET on entering or leaving softirq |
| 112 | * processing. |
| 113 | * |
| 114 | * - count is changed by SOFTIRQ_DISABLE_OFFSET (= 2 * SOFTIRQ_OFFSET) |
| 115 | * on local_bh_disable or local_bh_enable. |
| 116 | * |
| 117 | * This lets us distinguish between whether we are currently processing |
| 118 | * softirq and whether we just have bh disabled. |
| 119 | */ |
| 120 | #ifdef CONFIG_PREEMPT_RT |
| 121 | |
| 122 | /* |
| 123 | * RT accounts for BH disabled sections in task::softirqs_disabled_cnt and |
| 124 | * also in per CPU softirq_ctrl::cnt. This is necessary to allow tasks in a |
| 125 | * softirq disabled section to be preempted. |
| 126 | * |
| 127 | * The per task counter is used for softirq_count(), in_softirq() and |
| 128 | * in_serving_softirqs() because these counts are only valid when the task |
| 129 | * holding softirq_ctrl::lock is running. |
| 130 | * |
| 131 | * The per CPU counter prevents pointless wakeups of ksoftirqd in case that |
| 132 | * the task which is in a softirq disabled section is preempted or blocks. |
| 133 | */ |
| 134 | struct softirq_ctrl { |
| 135 | local_lock_t lock; |
| 136 | int cnt; |
| 137 | }; |
| 138 | |
| 139 | static DEFINE_PER_CPU(struct softirq_ctrl, softirq_ctrl) = { |
| 140 | .lock = INIT_LOCAL_LOCK(softirq_ctrl.lock), |
| 141 | }; |
| 142 | |
| 143 | /** |
| 144 | * local_bh_blocked() - Check for idle whether BH processing is blocked |
| 145 | * |
| 146 | * Returns false if the per CPU softirq::cnt is 0 otherwise true. |
| 147 | * |
| 148 | * This is invoked from the idle task to guard against false positive |
| 149 | * softirq pending warnings, which would happen when the task which holds |
| 150 | * softirq_ctrl::lock was the only running task on the CPU and blocks on |
| 151 | * some other lock. |
| 152 | */ |
| 153 | bool local_bh_blocked(void) |
| 154 | { |
| 155 | return __this_cpu_read(softirq_ctrl.cnt) != 0; |
| 156 | } |
| 157 | |
| 158 | void __local_bh_disable_ip(unsigned long ip, unsigned int cnt) |
| 159 | { |
| 160 | unsigned long flags; |
| 161 | int newcnt; |
| 162 | |
| 163 | WARN_ON_ONCE(in_hardirq()); |
| 164 | |
| 165 | /* First entry of a task into a BH disabled section? */ |
| 166 | if (!current->softirq_disable_cnt) { |
| 167 | if (preemptible()) { |
| 168 | local_lock(&softirq_ctrl.lock); |
| 169 | /* Required to meet the RCU bottomhalf requirements. */ |
| 170 | rcu_read_lock(); |
| 171 | } else { |
| 172 | DEBUG_LOCKS_WARN_ON(this_cpu_read(softirq_ctrl.cnt)); |
| 173 | } |
| 174 | } |
| 175 | |
| 176 | /* |
| 177 | * Track the per CPU softirq disabled state. On RT this is per CPU |
| 178 | * state to allow preemption of bottom half disabled sections. |
| 179 | */ |
| 180 | newcnt = __this_cpu_add_return(softirq_ctrl.cnt, cnt); |
| 181 | /* |
| 182 | * Reflect the result in the task state to prevent recursion on the |
| 183 | * local lock and to make softirq_count() & al work. |
| 184 | */ |
| 185 | current->softirq_disable_cnt = newcnt; |
| 186 | |
| 187 | if (IS_ENABLED(CONFIG_TRACE_IRQFLAGS) && newcnt == cnt) { |
| 188 | raw_local_irq_save(flags); |
| 189 | lockdep_softirqs_off(ip); |
| 190 | raw_local_irq_restore(flags); |
| 191 | } |
| 192 | } |
| 193 | EXPORT_SYMBOL(__local_bh_disable_ip); |
| 194 | |
| 195 | static void __local_bh_enable(unsigned int cnt, bool unlock) |
| 196 | { |
| 197 | unsigned long flags; |
| 198 | int newcnt; |
| 199 | |
| 200 | DEBUG_LOCKS_WARN_ON(current->softirq_disable_cnt != |
| 201 | this_cpu_read(softirq_ctrl.cnt)); |
| 202 | |
| 203 | if (IS_ENABLED(CONFIG_TRACE_IRQFLAGS) && softirq_count() == cnt) { |
| 204 | raw_local_irq_save(flags); |
| 205 | lockdep_softirqs_on(_RET_IP_); |
| 206 | raw_local_irq_restore(flags); |
| 207 | } |
| 208 | |
| 209 | newcnt = __this_cpu_sub_return(softirq_ctrl.cnt, cnt); |
| 210 | current->softirq_disable_cnt = newcnt; |
| 211 | |
| 212 | if (!newcnt && unlock) { |
| 213 | rcu_read_unlock(); |
| 214 | local_unlock(&softirq_ctrl.lock); |
| 215 | } |
| 216 | } |
| 217 | |
| 218 | void __local_bh_enable_ip(unsigned long ip, unsigned int cnt) |
| 219 | { |
| 220 | bool preempt_on = preemptible(); |
| 221 | unsigned long flags; |
| 222 | u32 pending; |
| 223 | int curcnt; |
| 224 | |
| 225 | WARN_ON_ONCE(in_hardirq()); |
| 226 | lockdep_assert_irqs_enabled(); |
| 227 | |
| 228 | local_irq_save(flags); |
| 229 | curcnt = __this_cpu_read(softirq_ctrl.cnt); |
| 230 | |
| 231 | /* |
| 232 | * If this is not reenabling soft interrupts, no point in trying to |
| 233 | * run pending ones. |
| 234 | */ |
| 235 | if (curcnt != cnt) |
| 236 | goto out; |
| 237 | |
| 238 | pending = local_softirq_pending(); |
| 239 | if (!pending || ksoftirqd_running(pending)) |
| 240 | goto out; |
| 241 | |
| 242 | /* |
| 243 | * If this was called from non preemptible context, wake up the |
| 244 | * softirq daemon. |
| 245 | */ |
| 246 | if (!preempt_on) { |
| 247 | wakeup_softirqd(); |
| 248 | goto out; |
| 249 | } |
| 250 | |
| 251 | /* |
| 252 | * Adjust softirq count to SOFTIRQ_OFFSET which makes |
| 253 | * in_serving_softirq() become true. |
| 254 | */ |
| 255 | cnt = SOFTIRQ_OFFSET; |
| 256 | __local_bh_enable(cnt, false); |
| 257 | __do_softirq(); |
| 258 | |
| 259 | out: |
| 260 | __local_bh_enable(cnt, preempt_on); |
| 261 | local_irq_restore(flags); |
| 262 | } |
| 263 | EXPORT_SYMBOL(__local_bh_enable_ip); |
| 264 | |
| 265 | /* |
| 266 | * Invoked from ksoftirqd_run() outside of the interrupt disabled section |
| 267 | * to acquire the per CPU local lock for reentrancy protection. |
| 268 | */ |
| 269 | static inline void ksoftirqd_run_begin(void) |
| 270 | { |
| 271 | __local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET); |
| 272 | local_irq_disable(); |
| 273 | } |
| 274 | |
| 275 | /* Counterpart to ksoftirqd_run_begin() */ |
| 276 | static inline void ksoftirqd_run_end(void) |
| 277 | { |
| 278 | __local_bh_enable(SOFTIRQ_OFFSET, true); |
| 279 | WARN_ON_ONCE(in_interrupt()); |
| 280 | local_irq_enable(); |
| 281 | } |
| 282 | |
| 283 | static inline void softirq_handle_begin(void) { } |
| 284 | static inline void softirq_handle_end(void) { } |
| 285 | |
| 286 | static inline bool should_wake_ksoftirqd(void) |
| 287 | { |
| 288 | return !this_cpu_read(softirq_ctrl.cnt); |
| 289 | } |
| 290 | |
| 291 | static inline void invoke_softirq(void) |
| 292 | { |
| 293 | if (should_wake_ksoftirqd()) |
| 294 | wakeup_softirqd(); |
| 295 | } |
| 296 | |
| 297 | /* |
| 298 | * flush_smp_call_function_queue() can raise a soft interrupt in a function |
| 299 | * call. On RT kernels this is undesired and the only known functionality |
| 300 | * in the block layer which does this is disabled on RT. If soft interrupts |
| 301 | * get raised which haven't been raised before the flush, warn so it can be |
| 302 | * investigated. |
| 303 | */ |
| 304 | void do_softirq_post_smp_call_flush(unsigned int was_pending) |
| 305 | { |
| 306 | if (WARN_ON_ONCE(was_pending != local_softirq_pending())) |
| 307 | invoke_softirq(); |
| 308 | } |
| 309 | |
| 310 | #else /* CONFIG_PREEMPT_RT */ |
| 311 | |
| 312 | /* |
| 313 | * This one is for softirq.c-internal use, where hardirqs are disabled |
| 314 | * legitimately: |
| 315 | */ |
| 316 | #ifdef CONFIG_TRACE_IRQFLAGS |
| 317 | void __local_bh_disable_ip(unsigned long ip, unsigned int cnt) |
| 318 | { |
| 319 | unsigned long flags; |
| 320 | |
| 321 | WARN_ON_ONCE(in_hardirq()); |
| 322 | |
| 323 | raw_local_irq_save(flags); |
| 324 | /* |
| 325 | * The preempt tracer hooks into preempt_count_add and will break |
| 326 | * lockdep because it calls back into lockdep after SOFTIRQ_OFFSET |
| 327 | * is set and before current->softirq_enabled is cleared. |
| 328 | * We must manually increment preempt_count here and manually |
| 329 | * call the trace_preempt_off later. |
| 330 | */ |
| 331 | __preempt_count_add(cnt); |
| 332 | /* |
| 333 | * Were softirqs turned off above: |
| 334 | */ |
| 335 | if (softirq_count() == (cnt & SOFTIRQ_MASK)) |
| 336 | lockdep_softirqs_off(ip); |
| 337 | raw_local_irq_restore(flags); |
| 338 | |
| 339 | if (preempt_count() == cnt) { |
| 340 | #ifdef CONFIG_DEBUG_PREEMPT |
| 341 | current->preempt_disable_ip = get_lock_parent_ip(); |
| 342 | #endif |
| 343 | trace_preempt_off(CALLER_ADDR0, get_lock_parent_ip()); |
| 344 | } |
| 345 | } |
| 346 | EXPORT_SYMBOL(__local_bh_disable_ip); |
| 347 | #endif /* CONFIG_TRACE_IRQFLAGS */ |
| 348 | |
| 349 | static void __local_bh_enable(unsigned int cnt) |
| 350 | { |
| 351 | lockdep_assert_irqs_disabled(); |
| 352 | |
| 353 | if (preempt_count() == cnt) |
| 354 | trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip()); |
| 355 | |
| 356 | if (softirq_count() == (cnt & SOFTIRQ_MASK)) |
| 357 | lockdep_softirqs_on(_RET_IP_); |
| 358 | |
| 359 | __preempt_count_sub(cnt); |
| 360 | } |
| 361 | |
| 362 | /* |
| 363 | * Special-case - softirqs can safely be enabled by __do_softirq(), |
| 364 | * without processing still-pending softirqs: |
| 365 | */ |
| 366 | void _local_bh_enable(void) |
| 367 | { |
| 368 | WARN_ON_ONCE(in_hardirq()); |
| 369 | __local_bh_enable(SOFTIRQ_DISABLE_OFFSET); |
| 370 | } |
| 371 | EXPORT_SYMBOL(_local_bh_enable); |
| 372 | |
| 373 | void __local_bh_enable_ip(unsigned long ip, unsigned int cnt) |
| 374 | { |
| 375 | WARN_ON_ONCE(in_hardirq()); |
| 376 | lockdep_assert_irqs_enabled(); |
| 377 | #ifdef CONFIG_TRACE_IRQFLAGS |
| 378 | local_irq_disable(); |
| 379 | #endif |
| 380 | /* |
| 381 | * Are softirqs going to be turned on now: |
| 382 | */ |
| 383 | if (softirq_count() == SOFTIRQ_DISABLE_OFFSET) |
| 384 | lockdep_softirqs_on(ip); |
| 385 | /* |
| 386 | * Keep preemption disabled until we are done with |
| 387 | * softirq processing: |
| 388 | */ |
| 389 | __preempt_count_sub(cnt - 1); |
| 390 | |
| 391 | if (unlikely(!in_interrupt() && local_softirq_pending())) { |
| 392 | /* |
| 393 | * Run softirq if any pending. And do it in its own stack |
| 394 | * as we may be calling this deep in a task call stack already. |
| 395 | */ |
| 396 | do_softirq(); |
| 397 | } |
| 398 | |
| 399 | preempt_count_dec(); |
| 400 | #ifdef CONFIG_TRACE_IRQFLAGS |
| 401 | local_irq_enable(); |
| 402 | #endif |
| 403 | preempt_check_resched(); |
| 404 | } |
| 405 | EXPORT_SYMBOL(__local_bh_enable_ip); |
| 406 | |
| 407 | static inline void softirq_handle_begin(void) |
| 408 | { |
| 409 | __local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET); |
| 410 | } |
| 411 | |
| 412 | static inline void softirq_handle_end(void) |
| 413 | { |
| 414 | __local_bh_enable(SOFTIRQ_OFFSET); |
| 415 | WARN_ON_ONCE(in_interrupt()); |
| 416 | } |
| 417 | |
| 418 | static inline void ksoftirqd_run_begin(void) |
| 419 | { |
| 420 | local_irq_disable(); |
| 421 | } |
| 422 | |
| 423 | static inline void ksoftirqd_run_end(void) |
| 424 | { |
| 425 | local_irq_enable(); |
| 426 | } |
| 427 | |
| 428 | static inline bool should_wake_ksoftirqd(void) |
| 429 | { |
| 430 | return true; |
| 431 | } |
| 432 | |
| 433 | static inline void invoke_softirq(void) |
| 434 | { |
| 435 | if (ksoftirqd_running(local_softirq_pending())) |
| 436 | return; |
| 437 | |
| 438 | if (!force_irqthreads() || !__this_cpu_read(ksoftirqd)) { |
| 439 | #ifdef CONFIG_HAVE_IRQ_EXIT_ON_IRQ_STACK |
| 440 | /* |
| 441 | * We can safely execute softirq on the current stack if |
| 442 | * it is the irq stack, because it should be near empty |
| 443 | * at this stage. |
| 444 | */ |
| 445 | __do_softirq(); |
| 446 | #else |
| 447 | /* |
| 448 | * Otherwise, irq_exit() is called on the task stack that can |
| 449 | * be potentially deep already. So call softirq in its own stack |
| 450 | * to prevent from any overrun. |
| 451 | */ |
| 452 | do_softirq_own_stack(); |
| 453 | #endif |
| 454 | } else { |
| 455 | wakeup_softirqd(); |
| 456 | } |
| 457 | } |
| 458 | |
| 459 | asmlinkage __visible void do_softirq(void) |
| 460 | { |
| 461 | __u32 pending; |
| 462 | unsigned long flags; |
| 463 | |
| 464 | if (in_interrupt()) |
| 465 | return; |
| 466 | |
| 467 | local_irq_save(flags); |
| 468 | |
| 469 | pending = local_softirq_pending(); |
| 470 | |
| 471 | if (pending && !ksoftirqd_running(pending)) |
| 472 | do_softirq_own_stack(); |
| 473 | |
| 474 | local_irq_restore(flags); |
| 475 | } |
| 476 | |
| 477 | #endif /* !CONFIG_PREEMPT_RT */ |
| 478 | |
| 479 | /* |
| 480 | * We restart softirq processing for at most MAX_SOFTIRQ_RESTART times, |
| 481 | * but break the loop if need_resched() is set or after 2 ms. |
| 482 | * The MAX_SOFTIRQ_TIME provides a nice upper bound in most cases, but in |
| 483 | * certain cases, such as stop_machine(), jiffies may cease to |
| 484 | * increment and so we need the MAX_SOFTIRQ_RESTART limit as |
| 485 | * well to make sure we eventually return from this method. |
| 486 | * |
| 487 | * These limits have been established via experimentation. |
| 488 | * The two things to balance is latency against fairness - |
| 489 | * we want to handle softirqs as soon as possible, but they |
| 490 | * should not be able to lock up the box. |
| 491 | */ |
| 492 | #define MAX_SOFTIRQ_TIME msecs_to_jiffies(2) |
| 493 | #define MAX_SOFTIRQ_RESTART 10 |
| 494 | |
| 495 | #ifdef CONFIG_TRACE_IRQFLAGS |
| 496 | /* |
| 497 | * When we run softirqs from irq_exit() and thus on the hardirq stack we need |
| 498 | * to keep the lockdep irq context tracking as tight as possible in order to |
| 499 | * not miss-qualify lock contexts and miss possible deadlocks. |
| 500 | */ |
| 501 | |
| 502 | static inline bool lockdep_softirq_start(void) |
| 503 | { |
| 504 | bool in_hardirq = false; |
| 505 | |
| 506 | if (lockdep_hardirq_context()) { |
| 507 | in_hardirq = true; |
| 508 | lockdep_hardirq_exit(); |
| 509 | } |
| 510 | |
| 511 | lockdep_softirq_enter(); |
| 512 | |
| 513 | return in_hardirq; |
| 514 | } |
| 515 | |
| 516 | static inline void lockdep_softirq_end(bool in_hardirq) |
| 517 | { |
| 518 | lockdep_softirq_exit(); |
| 519 | |
| 520 | if (in_hardirq) |
| 521 | lockdep_hardirq_enter(); |
| 522 | } |
| 523 | #else |
| 524 | static inline bool lockdep_softirq_start(void) { return false; } |
| 525 | static inline void lockdep_softirq_end(bool in_hardirq) { } |
| 526 | #endif |
| 527 | |
| 528 | asmlinkage __visible void __softirq_entry __do_softirq(void) |
| 529 | { |
| 530 | unsigned long end = jiffies + MAX_SOFTIRQ_TIME; |
| 531 | unsigned long old_flags = current->flags; |
| 532 | int max_restart = MAX_SOFTIRQ_RESTART; |
| 533 | struct softirq_action *h; |
| 534 | bool in_hardirq; |
| 535 | __u32 pending; |
| 536 | int softirq_bit; |
| 537 | |
| 538 | /* |
| 539 | * Mask out PF_MEMALLOC as the current task context is borrowed for the |
| 540 | * softirq. A softirq handled, such as network RX, might set PF_MEMALLOC |
| 541 | * again if the socket is related to swapping. |
| 542 | */ |
| 543 | current->flags &= ~PF_MEMALLOC; |
| 544 | |
| 545 | pending = local_softirq_pending(); |
| 546 | |
| 547 | softirq_handle_begin(); |
| 548 | in_hardirq = lockdep_softirq_start(); |
| 549 | account_softirq_enter(current); |
| 550 | |
| 551 | restart: |
| 552 | /* Reset the pending bitmask before enabling irqs */ |
| 553 | set_softirq_pending(0); |
| 554 | |
| 555 | local_irq_enable(); |
| 556 | |
| 557 | h = softirq_vec; |
| 558 | |
| 559 | while ((softirq_bit = ffs(pending))) { |
| 560 | unsigned int vec_nr; |
| 561 | int prev_count; |
| 562 | |
| 563 | h += softirq_bit - 1; |
| 564 | |
| 565 | vec_nr = h - softirq_vec; |
| 566 | prev_count = preempt_count(); |
| 567 | |
| 568 | kstat_incr_softirqs_this_cpu(vec_nr); |
| 569 | |
| 570 | trace_softirq_entry(vec_nr); |
| 571 | h->action(h); |
| 572 | trace_softirq_exit(vec_nr); |
| 573 | if (unlikely(prev_count != preempt_count())) { |
| 574 | pr_err("huh, entered softirq %u %s %p with preempt_count %08x, exited with %08x?\n", |
| 575 | vec_nr, softirq_to_name[vec_nr], h->action, |
| 576 | prev_count, preempt_count()); |
| 577 | preempt_count_set(prev_count); |
| 578 | } |
| 579 | h++; |
| 580 | pending >>= softirq_bit; |
| 581 | } |
| 582 | |
| 583 | if (!IS_ENABLED(CONFIG_PREEMPT_RT) && |
| 584 | __this_cpu_read(ksoftirqd) == current) |
| 585 | rcu_softirq_qs(); |
| 586 | |
| 587 | local_irq_disable(); |
| 588 | |
| 589 | pending = local_softirq_pending(); |
| 590 | if (pending) { |
| 591 | if (time_before(jiffies, end) && !need_resched() && |
| 592 | --max_restart) |
| 593 | goto restart; |
| 594 | |
| 595 | wakeup_softirqd(); |
| 596 | } |
| 597 | |
| 598 | account_softirq_exit(current); |
| 599 | lockdep_softirq_end(in_hardirq); |
| 600 | softirq_handle_end(); |
| 601 | current_restore_flags(old_flags, PF_MEMALLOC); |
| 602 | } |
| 603 | |
| 604 | /** |
| 605 | * irq_enter_rcu - Enter an interrupt context with RCU watching |
| 606 | */ |
| 607 | void irq_enter_rcu(void) |
| 608 | { |
| 609 | __irq_enter_raw(); |
| 610 | |
| 611 | if (tick_nohz_full_cpu(smp_processor_id()) || |
| 612 | (is_idle_task(current) && (irq_count() == HARDIRQ_OFFSET))) |
| 613 | tick_irq_enter(); |
| 614 | |
| 615 | account_hardirq_enter(current); |
| 616 | } |
| 617 | |
| 618 | /** |
| 619 | * irq_enter - Enter an interrupt context including RCU update |
| 620 | */ |
| 621 | void irq_enter(void) |
| 622 | { |
| 623 | ct_irq_enter(); |
| 624 | irq_enter_rcu(); |
| 625 | } |
| 626 | |
| 627 | static inline void tick_irq_exit(void) |
| 628 | { |
| 629 | #ifdef CONFIG_NO_HZ_COMMON |
| 630 | int cpu = smp_processor_id(); |
| 631 | |
| 632 | /* Make sure that timer wheel updates are propagated */ |
| 633 | if ((idle_cpu(cpu) && !need_resched()) || tick_nohz_full_cpu(cpu)) { |
| 634 | if (!in_hardirq()) |
| 635 | tick_nohz_irq_exit(); |
| 636 | } |
| 637 | #endif |
| 638 | } |
| 639 | |
| 640 | static inline void __irq_exit_rcu(void) |
| 641 | { |
| 642 | #ifndef __ARCH_IRQ_EXIT_IRQS_DISABLED |
| 643 | local_irq_disable(); |
| 644 | #else |
| 645 | lockdep_assert_irqs_disabled(); |
| 646 | #endif |
| 647 | account_hardirq_exit(current); |
| 648 | preempt_count_sub(HARDIRQ_OFFSET); |
| 649 | if (!in_interrupt() && local_softirq_pending()) |
| 650 | invoke_softirq(); |
| 651 | |
| 652 | tick_irq_exit(); |
| 653 | } |
| 654 | |
| 655 | /** |
| 656 | * irq_exit_rcu() - Exit an interrupt context without updating RCU |
| 657 | * |
| 658 | * Also processes softirqs if needed and possible. |
| 659 | */ |
| 660 | void irq_exit_rcu(void) |
| 661 | { |
| 662 | __irq_exit_rcu(); |
| 663 | /* must be last! */ |
| 664 | lockdep_hardirq_exit(); |
| 665 | } |
| 666 | |
| 667 | /** |
| 668 | * irq_exit - Exit an interrupt context, update RCU and lockdep |
| 669 | * |
| 670 | * Also processes softirqs if needed and possible. |
| 671 | */ |
| 672 | void irq_exit(void) |
| 673 | { |
| 674 | __irq_exit_rcu(); |
| 675 | ct_irq_exit(); |
| 676 | /* must be last! */ |
| 677 | lockdep_hardirq_exit(); |
| 678 | } |
| 679 | |
| 680 | /* |
| 681 | * This function must run with irqs disabled! |
| 682 | */ |
| 683 | inline void raise_softirq_irqoff(unsigned int nr) |
| 684 | { |
| 685 | __raise_softirq_irqoff(nr); |
| 686 | |
| 687 | /* |
| 688 | * If we're in an interrupt or softirq, we're done |
| 689 | * (this also catches softirq-disabled code). We will |
| 690 | * actually run the softirq once we return from |
| 691 | * the irq or softirq. |
| 692 | * |
| 693 | * Otherwise we wake up ksoftirqd to make sure we |
| 694 | * schedule the softirq soon. |
| 695 | */ |
| 696 | if (!in_interrupt() && should_wake_ksoftirqd()) |
| 697 | wakeup_softirqd(); |
| 698 | } |
| 699 | |
| 700 | void raise_softirq(unsigned int nr) |
| 701 | { |
| 702 | unsigned long flags; |
| 703 | |
| 704 | local_irq_save(flags); |
| 705 | raise_softirq_irqoff(nr); |
| 706 | local_irq_restore(flags); |
| 707 | } |
| 708 | |
| 709 | void __raise_softirq_irqoff(unsigned int nr) |
| 710 | { |
| 711 | lockdep_assert_irqs_disabled(); |
| 712 | trace_softirq_raise(nr); |
| 713 | or_softirq_pending(1UL << nr); |
| 714 | } |
| 715 | |
| 716 | void open_softirq(int nr, void (*action)(struct softirq_action *)) |
| 717 | { |
| 718 | softirq_vec[nr].action = action; |
| 719 | } |
| 720 | |
| 721 | /* |
| 722 | * Tasklets |
| 723 | */ |
| 724 | struct tasklet_head { |
| 725 | struct tasklet_struct *head; |
| 726 | struct tasklet_struct **tail; |
| 727 | }; |
| 728 | |
| 729 | static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec); |
| 730 | static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec); |
| 731 | |
| 732 | static void __tasklet_schedule_common(struct tasklet_struct *t, |
| 733 | struct tasklet_head __percpu *headp, |
| 734 | unsigned int softirq_nr) |
| 735 | { |
| 736 | struct tasklet_head *head; |
| 737 | unsigned long flags; |
| 738 | |
| 739 | local_irq_save(flags); |
| 740 | head = this_cpu_ptr(headp); |
| 741 | t->next = NULL; |
| 742 | *head->tail = t; |
| 743 | head->tail = &(t->next); |
| 744 | raise_softirq_irqoff(softirq_nr); |
| 745 | local_irq_restore(flags); |
| 746 | } |
| 747 | |
| 748 | void __tasklet_schedule(struct tasklet_struct *t) |
| 749 | { |
| 750 | __tasklet_schedule_common(t, &tasklet_vec, |
| 751 | TASKLET_SOFTIRQ); |
| 752 | } |
| 753 | EXPORT_SYMBOL(__tasklet_schedule); |
| 754 | |
| 755 | void __tasklet_hi_schedule(struct tasklet_struct *t) |
| 756 | { |
| 757 | __tasklet_schedule_common(t, &tasklet_hi_vec, |
| 758 | HI_SOFTIRQ); |
| 759 | } |
| 760 | EXPORT_SYMBOL(__tasklet_hi_schedule); |
| 761 | |
| 762 | static bool tasklet_clear_sched(struct tasklet_struct *t) |
| 763 | { |
| 764 | if (test_and_clear_bit(TASKLET_STATE_SCHED, &t->state)) { |
| 765 | wake_up_var(&t->state); |
| 766 | return true; |
| 767 | } |
| 768 | |
| 769 | WARN_ONCE(1, "tasklet SCHED state not set: %s %pS\n", |
| 770 | t->use_callback ? "callback" : "func", |
| 771 | t->use_callback ? (void *)t->callback : (void *)t->func); |
| 772 | |
| 773 | return false; |
| 774 | } |
| 775 | |
| 776 | static void tasklet_action_common(struct softirq_action *a, |
| 777 | struct tasklet_head *tl_head, |
| 778 | unsigned int softirq_nr) |
| 779 | { |
| 780 | struct tasklet_struct *list; |
| 781 | |
| 782 | local_irq_disable(); |
| 783 | list = tl_head->head; |
| 784 | tl_head->head = NULL; |
| 785 | tl_head->tail = &tl_head->head; |
| 786 | local_irq_enable(); |
| 787 | |
| 788 | while (list) { |
| 789 | struct tasklet_struct *t = list; |
| 790 | |
| 791 | list = list->next; |
| 792 | |
| 793 | if (tasklet_trylock(t)) { |
| 794 | if (!atomic_read(&t->count)) { |
| 795 | if (tasklet_clear_sched(t)) { |
| 796 | if (t->use_callback) |
| 797 | t->callback(t); |
| 798 | else |
| 799 | t->func(t->data); |
| 800 | } |
| 801 | tasklet_unlock(t); |
| 802 | continue; |
| 803 | } |
| 804 | tasklet_unlock(t); |
| 805 | } |
| 806 | |
| 807 | local_irq_disable(); |
| 808 | t->next = NULL; |
| 809 | *tl_head->tail = t; |
| 810 | tl_head->tail = &t->next; |
| 811 | __raise_softirq_irqoff(softirq_nr); |
| 812 | local_irq_enable(); |
| 813 | } |
| 814 | } |
| 815 | |
| 816 | static __latent_entropy void tasklet_action(struct softirq_action *a) |
| 817 | { |
| 818 | tasklet_action_common(a, this_cpu_ptr(&tasklet_vec), TASKLET_SOFTIRQ); |
| 819 | } |
| 820 | |
| 821 | static __latent_entropy void tasklet_hi_action(struct softirq_action *a) |
| 822 | { |
| 823 | tasklet_action_common(a, this_cpu_ptr(&tasklet_hi_vec), HI_SOFTIRQ); |
| 824 | } |
| 825 | |
| 826 | void tasklet_setup(struct tasklet_struct *t, |
| 827 | void (*callback)(struct tasklet_struct *)) |
| 828 | { |
| 829 | t->next = NULL; |
| 830 | t->state = 0; |
| 831 | atomic_set(&t->count, 0); |
| 832 | t->callback = callback; |
| 833 | t->use_callback = true; |
| 834 | t->data = 0; |
| 835 | } |
| 836 | EXPORT_SYMBOL(tasklet_setup); |
| 837 | |
| 838 | void tasklet_init(struct tasklet_struct *t, |
| 839 | void (*func)(unsigned long), unsigned long data) |
| 840 | { |
| 841 | t->next = NULL; |
| 842 | t->state = 0; |
| 843 | atomic_set(&t->count, 0); |
| 844 | t->func = func; |
| 845 | t->use_callback = false; |
| 846 | t->data = data; |
| 847 | } |
| 848 | EXPORT_SYMBOL(tasklet_init); |
| 849 | |
| 850 | #if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT) |
| 851 | /* |
| 852 | * Do not use in new code. Waiting for tasklets from atomic contexts is |
| 853 | * error prone and should be avoided. |
| 854 | */ |
| 855 | void tasklet_unlock_spin_wait(struct tasklet_struct *t) |
| 856 | { |
| 857 | while (test_bit(TASKLET_STATE_RUN, &(t)->state)) { |
| 858 | if (IS_ENABLED(CONFIG_PREEMPT_RT)) { |
| 859 | /* |
| 860 | * Prevent a live lock when current preempted soft |
| 861 | * interrupt processing or prevents ksoftirqd from |
| 862 | * running. If the tasklet runs on a different CPU |
| 863 | * then this has no effect other than doing the BH |
| 864 | * disable/enable dance for nothing. |
| 865 | */ |
| 866 | local_bh_disable(); |
| 867 | local_bh_enable(); |
| 868 | } else { |
| 869 | cpu_relax(); |
| 870 | } |
| 871 | } |
| 872 | } |
| 873 | EXPORT_SYMBOL(tasklet_unlock_spin_wait); |
| 874 | #endif |
| 875 | |
| 876 | void tasklet_kill(struct tasklet_struct *t) |
| 877 | { |
| 878 | if (in_interrupt()) |
| 879 | pr_notice("Attempt to kill tasklet from interrupt\n"); |
| 880 | |
| 881 | while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) |
| 882 | wait_var_event(&t->state, !test_bit(TASKLET_STATE_SCHED, &t->state)); |
| 883 | |
| 884 | tasklet_unlock_wait(t); |
| 885 | tasklet_clear_sched(t); |
| 886 | } |
| 887 | EXPORT_SYMBOL(tasklet_kill); |
| 888 | |
| 889 | #if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT) |
| 890 | void tasklet_unlock(struct tasklet_struct *t) |
| 891 | { |
| 892 | smp_mb__before_atomic(); |
| 893 | clear_bit(TASKLET_STATE_RUN, &t->state); |
| 894 | smp_mb__after_atomic(); |
| 895 | wake_up_var(&t->state); |
| 896 | } |
| 897 | EXPORT_SYMBOL_GPL(tasklet_unlock); |
| 898 | |
| 899 | void tasklet_unlock_wait(struct tasklet_struct *t) |
| 900 | { |
| 901 | wait_var_event(&t->state, !test_bit(TASKLET_STATE_RUN, &t->state)); |
| 902 | } |
| 903 | EXPORT_SYMBOL_GPL(tasklet_unlock_wait); |
| 904 | #endif |
| 905 | |
| 906 | void __init softirq_init(void) |
| 907 | { |
| 908 | int cpu; |
| 909 | |
| 910 | for_each_possible_cpu(cpu) { |
| 911 | per_cpu(tasklet_vec, cpu).tail = |
| 912 | &per_cpu(tasklet_vec, cpu).head; |
| 913 | per_cpu(tasklet_hi_vec, cpu).tail = |
| 914 | &per_cpu(tasklet_hi_vec, cpu).head; |
| 915 | } |
| 916 | |
| 917 | open_softirq(TASKLET_SOFTIRQ, tasklet_action); |
| 918 | open_softirq(HI_SOFTIRQ, tasklet_hi_action); |
| 919 | } |
| 920 | |
| 921 | static int ksoftirqd_should_run(unsigned int cpu) |
| 922 | { |
| 923 | return local_softirq_pending(); |
| 924 | } |
| 925 | |
| 926 | static void run_ksoftirqd(unsigned int cpu) |
| 927 | { |
| 928 | ksoftirqd_run_begin(); |
| 929 | if (local_softirq_pending()) { |
| 930 | /* |
| 931 | * We can safely run softirq on inline stack, as we are not deep |
| 932 | * in the task stack here. |
| 933 | */ |
| 934 | __do_softirq(); |
| 935 | ksoftirqd_run_end(); |
| 936 | cond_resched(); |
| 937 | return; |
| 938 | } |
| 939 | ksoftirqd_run_end(); |
| 940 | } |
| 941 | |
| 942 | #ifdef CONFIG_HOTPLUG_CPU |
| 943 | static int takeover_tasklets(unsigned int cpu) |
| 944 | { |
| 945 | /* CPU is dead, so no lock needed. */ |
| 946 | local_irq_disable(); |
| 947 | |
| 948 | /* Find end, append list for that CPU. */ |
| 949 | if (&per_cpu(tasklet_vec, cpu).head != per_cpu(tasklet_vec, cpu).tail) { |
| 950 | *__this_cpu_read(tasklet_vec.tail) = per_cpu(tasklet_vec, cpu).head; |
| 951 | __this_cpu_write(tasklet_vec.tail, per_cpu(tasklet_vec, cpu).tail); |
| 952 | per_cpu(tasklet_vec, cpu).head = NULL; |
| 953 | per_cpu(tasklet_vec, cpu).tail = &per_cpu(tasklet_vec, cpu).head; |
| 954 | } |
| 955 | raise_softirq_irqoff(TASKLET_SOFTIRQ); |
| 956 | |
| 957 | if (&per_cpu(tasklet_hi_vec, cpu).head != per_cpu(tasklet_hi_vec, cpu).tail) { |
| 958 | *__this_cpu_read(tasklet_hi_vec.tail) = per_cpu(tasklet_hi_vec, cpu).head; |
| 959 | __this_cpu_write(tasklet_hi_vec.tail, per_cpu(tasklet_hi_vec, cpu).tail); |
| 960 | per_cpu(tasklet_hi_vec, cpu).head = NULL; |
| 961 | per_cpu(tasklet_hi_vec, cpu).tail = &per_cpu(tasklet_hi_vec, cpu).head; |
| 962 | } |
| 963 | raise_softirq_irqoff(HI_SOFTIRQ); |
| 964 | |
| 965 | local_irq_enable(); |
| 966 | return 0; |
| 967 | } |
| 968 | #else |
| 969 | #define takeover_tasklets NULL |
| 970 | #endif /* CONFIG_HOTPLUG_CPU */ |
| 971 | |
| 972 | static struct smp_hotplug_thread softirq_threads = { |
| 973 | .store = &ksoftirqd, |
| 974 | .thread_should_run = ksoftirqd_should_run, |
| 975 | .thread_fn = run_ksoftirqd, |
| 976 | .thread_comm = "ksoftirqd/%u", |
| 977 | }; |
| 978 | |
| 979 | static __init int spawn_ksoftirqd(void) |
| 980 | { |
| 981 | cpuhp_setup_state_nocalls(CPUHP_SOFTIRQ_DEAD, "softirq:dead", NULL, |
| 982 | takeover_tasklets); |
| 983 | BUG_ON(smpboot_register_percpu_thread(&softirq_threads)); |
| 984 | |
| 985 | return 0; |
| 986 | } |
| 987 | early_initcall(spawn_ksoftirqd); |
| 988 | |
| 989 | /* |
| 990 | * [ These __weak aliases are kept in a separate compilation unit, so that |
| 991 | * GCC does not inline them incorrectly. ] |
| 992 | */ |
| 993 | |
| 994 | int __init __weak early_irq_init(void) |
| 995 | { |
| 996 | return 0; |
| 997 | } |
| 998 | |
| 999 | int __init __weak arch_probe_nr_irqs(void) |
| 1000 | { |
| 1001 | return NR_IRQS_LEGACY; |
| 1002 | } |
| 1003 | |
| 1004 | int __init __weak arch_early_irq_init(void) |
| 1005 | { |
| 1006 | return 0; |
| 1007 | } |
| 1008 | |
| 1009 | unsigned int __weak arch_dynirq_lower_bound(unsigned int from) |
| 1010 | { |
| 1011 | return from; |
| 1012 | } |