kernel/softirq.c

   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 #include <linux/workqueue.h>
  31
  32 #include <asm/softirq_stack.h>
  33
  34 #define CREATE_TRACE_POINTS
  35 #include <trace/events/irq.h>
  36
  37 /*
  38    - No shared variables, all the data are CPU local.
  39    - If a softirq needs serialization, let it serialize itself
  40      by its own spinlocks.
  41    - Even if softirq is serialized, only local cpu is marked for
  42      execution. Hence, we get something sort of weak cpu binding.
  43      Though it is still not clear, will it result in better locality
  44      or will not.
  45
  46    Examples:
  47    - NET RX softirq. It is multithreaded and does not require
  48      any global serialization.
  49    - NET TX softirq. It kicks software netdevice queues, hence
  50      it is logically serialized per device, but this serialization
  51      is invisible to common code.
  52    - Tasklets: serialized wrt itself.
  53  */
  54
  55 #ifndef __ARCH_IRQ_STAT
  56 DEFINE_PER_CPU_ALIGNED(irq_cpustat_t, irq_stat);
  57 EXPORT_PER_CPU_SYMBOL(irq_stat);
  58 #endif
  59
  60 static struct softirq_action softirq_vec[NR_SOFTIRQS] __cacheline_aligned_in_smp;
  61
  62 DEFINE_PER_CPU(struct task_struct *, ksoftirqd);
  63
  64 const char * const softirq_to_name[NR_SOFTIRQS] = {
  65         "HI", "TIMER", "NET_TX", "NET_RX", "BLOCK", "IRQ_POLL",
  66         "TASKLET", "SCHED", "HRTIMER", "RCU"
  67 };
  68
  69 /*
  70  * we cannot loop indefinitely here to avoid userspace starvation,
  71  * but we also don't want to introduce a worst case 1/HZ latency
  72  * to the pending events, so lets the scheduler to balance
  73  * the softirq load for us.
  74  */
  75 static void wakeup_softirqd(void)
  76 {
  77         /* Interrupts are disabled: no need to stop preemption */
  78         struct task_struct *tsk = __this_cpu_read(ksoftirqd);
  79
  80         if (tsk)
  81                 wake_up_process(tsk);
  82 }
  83
  84 #ifdef CONFIG_TRACE_IRQFLAGS
  85 DEFINE_PER_CPU(int, hardirqs_enabled);
  86 DEFINE_PER_CPU(int, hardirq_context);
  87 EXPORT_PER_CPU_SYMBOL_GPL(hardirqs_enabled);
  88 EXPORT_PER_CPU_SYMBOL_GPL(hardirq_context);
  89 #endif
  90
  91 /*
  92  * SOFTIRQ_OFFSET usage:
  93  *
  94  * On !RT kernels 'count' is the preempt counter, on RT kernels this applies
  95  * to a per CPU counter and to task::softirqs_disabled_cnt.
  96  *
  97  * - count is changed by SOFTIRQ_OFFSET on entering or leaving softirq
  98  *   processing.
  99  *
 100  * - count is changed by SOFTIRQ_DISABLE_OFFSET (= 2 * SOFTIRQ_OFFSET)
 101  *   on local_bh_disable or local_bh_enable.
 102  *
 103  * This lets us distinguish between whether we are currently processing
 104  * softirq and whether we just have bh disabled.
 105  */
 106 #ifdef CONFIG_PREEMPT_RT
 107
 108 /*
 109  * RT accounts for BH disabled sections in task::softirqs_disabled_cnt and
 110  * also in per CPU softirq_ctrl::cnt. This is necessary to allow tasks in a
 111  * softirq disabled section to be preempted.
 112  *
 113  * The per task counter is used for softirq_count(), in_softirq() and
 114  * in_serving_softirqs() because these counts are only valid when the task
 115  * holding softirq_ctrl::lock is running.
 116  *
 117  * The per CPU counter prevents pointless wakeups of ksoftirqd in case that
 118  * the task which is in a softirq disabled section is preempted or blocks.
 119  */
 120 struct softirq_ctrl {
 121         local_lock_t    lock;
 122         int             cnt;
 123 };
 124
 125 static DEFINE_PER_CPU(struct softirq_ctrl, softirq_ctrl) = {
 126         .lock   = INIT_LOCAL_LOCK(softirq_ctrl.lock),
 127 };
 128
 129 /**
 130  * local_bh_blocked() - Check for idle whether BH processing is blocked
 131  *
 132  * Returns false if the per CPU softirq::cnt is 0 otherwise true.
 133  *
 134  * This is invoked from the idle task to guard against false positive
 135  * softirq pending warnings, which would happen when the task which holds
 136  * softirq_ctrl::lock was the only running task on the CPU and blocks on
 137  * some other lock.
 138  */
 139 bool local_bh_blocked(void)
 140 {
 141         return __this_cpu_read(softirq_ctrl.cnt) != 0;
 142 }
 143
 144 void __local_bh_disable_ip(unsigned long ip, unsigned int cnt)
 145 {
 146         unsigned long flags;
 147         int newcnt;
 148
 149         WARN_ON_ONCE(in_hardirq());
 150
 151         /* First entry of a task into a BH disabled section? */
 152         if (!current->softirq_disable_cnt) {
 153                 if (preemptible()) {
 154                         local_lock(&softirq_ctrl.lock);
 155                         /* Required to meet the RCU bottomhalf requirements. */
 156                         rcu_read_lock();
 157                 } else {
 158                         DEBUG_LOCKS_WARN_ON(this_cpu_read(softirq_ctrl.cnt));
 159                 }
 160         }
 161
 162         /*
 163          * Track the per CPU softirq disabled state. On RT this is per CPU
 164          * state to allow preemption of bottom half disabled sections.
 165          */
 166         newcnt = __this_cpu_add_return(softirq_ctrl.cnt, cnt);
 167         /*
 168          * Reflect the result in the task state to prevent recursion on the
 169          * local lock and to make softirq_count() & al work.
 170          */
 171         current->softirq_disable_cnt = newcnt;
 172
 173         if (IS_ENABLED(CONFIG_TRACE_IRQFLAGS) && newcnt == cnt) {
 174                 raw_local_irq_save(flags);
 175                 lockdep_softirqs_off(ip);
 176                 raw_local_irq_restore(flags);
 177         }
 178 }
 179 EXPORT_SYMBOL(__local_bh_disable_ip);
 180
 181 static void __local_bh_enable(unsigned int cnt, bool unlock)
 182 {
 183         unsigned long flags;
 184         int newcnt;
 185
 186         DEBUG_LOCKS_WARN_ON(current->softirq_disable_cnt !=
 187                             this_cpu_read(softirq_ctrl.cnt));
 188
 189         if (IS_ENABLED(CONFIG_TRACE_IRQFLAGS) && softirq_count() == cnt) {
 190                 raw_local_irq_save(flags);
 191                 lockdep_softirqs_on(_RET_IP_);
 192                 raw_local_irq_restore(flags);
 193         }
 194
 195         newcnt = __this_cpu_sub_return(softirq_ctrl.cnt, cnt);
 196         current->softirq_disable_cnt = newcnt;
 197
 198         if (!newcnt && unlock) {
 199                 rcu_read_unlock();
 200                 local_unlock(&softirq_ctrl.lock);
 201         }
 202 }
 203
 204 void __local_bh_enable_ip(unsigned long ip, unsigned int cnt)
 205 {
 206         bool preempt_on = preemptible();
 207         unsigned long flags;
 208         u32 pending;
 209         int curcnt;
 210
 211         WARN_ON_ONCE(in_hardirq());
 212         lockdep_assert_irqs_enabled();
 213
 214         local_irq_save(flags);
 215         curcnt = __this_cpu_read(softirq_ctrl.cnt);
 216
 217         /*
 218          * If this is not reenabling soft interrupts, no point in trying to
 219          * run pending ones.
 220          */
 221         if (curcnt != cnt)
 222                 goto out;
 223
 224         pending = local_softirq_pending();
 225         if (!pending)
 226                 goto out;
 227
 228         /*
 229          * If this was called from non preemptible context, wake up the
 230          * softirq daemon.
 231          */
 232         if (!preempt_on) {
 233                 wakeup_softirqd();
 234                 goto out;
 235         }
 236
 237         /*
 238          * Adjust softirq count to SOFTIRQ_OFFSET which makes
 239          * in_serving_softirq() become true.
 240          */
 241         cnt = SOFTIRQ_OFFSET;
 242         __local_bh_enable(cnt, false);
 243         __do_softirq();
 244
 245 out:
 246         __local_bh_enable(cnt, preempt_on);
 247         local_irq_restore(flags);
 248 }
 249 EXPORT_SYMBOL(__local_bh_enable_ip);
 250
 251 /*
 252  * Invoked from ksoftirqd_run() outside of the interrupt disabled section
 253  * to acquire the per CPU local lock for reentrancy protection.
 254  */
 255 static inline void ksoftirqd_run_begin(void)
 256 {
 257         __local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET);
 258         local_irq_disable();
 259 }
 260
 261 /* Counterpart to ksoftirqd_run_begin() */
 262 static inline void ksoftirqd_run_end(void)
 263 {
 264         __local_bh_enable(SOFTIRQ_OFFSET, true);
 265         WARN_ON_ONCE(in_interrupt());
 266         local_irq_enable();
 267 }
 268
 269 static inline void softirq_handle_begin(void) { }
 270 static inline void softirq_handle_end(void) { }
 271
 272 static inline bool should_wake_ksoftirqd(void)
 273 {
 274         return !this_cpu_read(softirq_ctrl.cnt);
 275 }
 276
 277 static inline void invoke_softirq(void)
 278 {
 279         if (should_wake_ksoftirqd())
 280                 wakeup_softirqd();
 281 }
 282
 283 #define SCHED_SOFTIRQ_MASK      BIT(SCHED_SOFTIRQ)
 284
 285 /*
 286  * flush_smp_call_function_queue() can raise a soft interrupt in a function
 287  * call. On RT kernels this is undesired and the only known functionalities
 288  * are in the block layer which is disabled on RT, and in the scheduler for
 289  * idle load balancing. If soft interrupts get raised which haven't been
 290  * raised before the flush, warn if it is not a SCHED_SOFTIRQ so it can be
 291  * investigated.
 292  */
 293 void do_softirq_post_smp_call_flush(unsigned int was_pending)
 294 {
 295         unsigned int is_pending = local_softirq_pending();
 296
 297         if (unlikely(was_pending != is_pending)) {
 298                 WARN_ON_ONCE(was_pending != (is_pending & ~SCHED_SOFTIRQ_MASK));
 299                 invoke_softirq();
 300         }
 301 }
 302
 303 #else /* CONFIG_PREEMPT_RT */
 304
 305 /*
 306  * This one is for softirq.c-internal use, where hardirqs are disabled
 307  * legitimately:
 308  */
 309 #ifdef CONFIG_TRACE_IRQFLAGS
 310 void __local_bh_disable_ip(unsigned long ip, unsigned int cnt)
 311 {
 312         unsigned long flags;
 313
 314         WARN_ON_ONCE(in_hardirq());
 315
 316         raw_local_irq_save(flags);
 317         /*
 318          * The preempt tracer hooks into preempt_count_add and will break
 319          * lockdep because it calls back into lockdep after SOFTIRQ_OFFSET
 320          * is set and before current->softirq_enabled is cleared.
 321          * We must manually increment preempt_count here and manually
 322          * call the trace_preempt_off later.
 323          */
 324         __preempt_count_add(cnt);
 325         /*
 326          * Were softirqs turned off above:
 327          */
 328         if (softirq_count() == (cnt & SOFTIRQ_MASK))
 329                 lockdep_softirqs_off(ip);
 330         raw_local_irq_restore(flags);
 331
 332         if (preempt_count() == cnt) {
 333 #ifdef CONFIG_DEBUG_PREEMPT
 334                 current->preempt_disable_ip = get_lock_parent_ip();
 335 #endif
 336                 trace_preempt_off(CALLER_ADDR0, get_lock_parent_ip());
 337         }
 338 }
 339 EXPORT_SYMBOL(__local_bh_disable_ip);
 340 #endif /* CONFIG_TRACE_IRQFLAGS */
 341
 342 static void __local_bh_enable(unsigned int cnt)
 343 {
 344         lockdep_assert_irqs_disabled();
 345
 346         if (preempt_count() == cnt)
 347                 trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip());
 348
 349         if (softirq_count() == (cnt & SOFTIRQ_MASK))
 350                 lockdep_softirqs_on(_RET_IP_);
 351
 352         __preempt_count_sub(cnt);
 353 }
 354
 355 /*
 356  * Special-case - softirqs can safely be enabled by __do_softirq(),
 357  * without processing still-pending softirqs:
 358  */
 359 void _local_bh_enable(void)
 360 {
 361         WARN_ON_ONCE(in_hardirq());
 362         __local_bh_enable(SOFTIRQ_DISABLE_OFFSET);
 363 }
 364 EXPORT_SYMBOL(_local_bh_enable);
 365
 366 void __local_bh_enable_ip(unsigned long ip, unsigned int cnt)
 367 {
 368         WARN_ON_ONCE(in_hardirq());
 369         lockdep_assert_irqs_enabled();
 370 #ifdef CONFIG_TRACE_IRQFLAGS
 371         local_irq_disable();
 372 #endif
 373         /*
 374          * Are softirqs going to be turned on now:
 375          */
 376         if (softirq_count() == SOFTIRQ_DISABLE_OFFSET)
 377                 lockdep_softirqs_on(ip);
 378         /*
 379          * Keep preemption disabled until we are done with
 380          * softirq processing:
 381          */
 382         __preempt_count_sub(cnt - 1);
 383
 384         if (unlikely(!in_interrupt() && local_softirq_pending())) {
 385                 /*
 386                  * Run softirq if any pending. And do it in its own stack
 387                  * as we may be calling this deep in a task call stack already.
 388                  */
 389                 do_softirq();
 390         }
 391
 392         preempt_count_dec();
 393 #ifdef CONFIG_TRACE_IRQFLAGS
 394         local_irq_enable();
 395 #endif
 396         preempt_check_resched();
 397 }
 398 EXPORT_SYMBOL(__local_bh_enable_ip);
 399
 400 static inline void softirq_handle_begin(void)
 401 {
 402         __local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET);
 403 }
 404
 405 static inline void softirq_handle_end(void)
 406 {
 407         __local_bh_enable(SOFTIRQ_OFFSET);
 408         WARN_ON_ONCE(in_interrupt());
 409 }
 410
 411 static inline void ksoftirqd_run_begin(void)
 412 {
 413         local_irq_disable();
 414 }
 415
 416 static inline void ksoftirqd_run_end(void)
 417 {
 418         local_irq_enable();
 419 }
 420
 421 static inline bool should_wake_ksoftirqd(void)
 422 {
 423         return true;
 424 }
 425
 426 static inline void invoke_softirq(void)
 427 {
 428         if (!force_irqthreads() || !__this_cpu_read(ksoftirqd)) {
 429 #ifdef CONFIG_HAVE_IRQ_EXIT_ON_IRQ_STACK
 430                 /*
 431                  * We can safely execute softirq on the current stack if
 432                  * it is the irq stack, because it should be near empty
 433                  * at this stage.
 434                  */
 435                 __do_softirq();
 436 #else
 437                 /*
 438                  * Otherwise, irq_exit() is called on the task stack that can
 439                  * be potentially deep already. So call softirq in its own stack
 440                  * to prevent from any overrun.
 441                  */
 442                 do_softirq_own_stack();
 443 #endif
 444         } else {
 445                 wakeup_softirqd();
 446         }
 447 }
 448
 449 asmlinkage __visible void do_softirq(void)
 450 {
 451         __u32 pending;
 452         unsigned long flags;
 453
 454         if (in_interrupt())
 455                 return;
 456
 457         local_irq_save(flags);
 458
 459         pending = local_softirq_pending();
 460
 461         if (pending)
 462                 do_softirq_own_stack();
 463
 464         local_irq_restore(flags);
 465 }
 466
 467 #endif /* !CONFIG_PREEMPT_RT */
 468
 469 /*
 470  * We restart softirq processing for at most MAX_SOFTIRQ_RESTART times,
 471  * but break the loop if need_resched() is set or after 2 ms.
 472  * The MAX_SOFTIRQ_TIME provides a nice upper bound in most cases, but in
 473  * certain cases, such as stop_machine(), jiffies may cease to
 474  * increment and so we need the MAX_SOFTIRQ_RESTART limit as
 475  * well to make sure we eventually return from this method.
 476  *
 477  * These limits have been established via experimentation.
 478  * The two things to balance is latency against fairness -
 479  * we want to handle softirqs as soon as possible, but they
 480  * should not be able to lock up the box.
 481  */
 482 #define MAX_SOFTIRQ_TIME  msecs_to_jiffies(2)
 483 #define MAX_SOFTIRQ_RESTART 10
 484
 485 #ifdef CONFIG_TRACE_IRQFLAGS
 486 /*
 487  * When we run softirqs from irq_exit() and thus on the hardirq stack we need
 488  * to keep the lockdep irq context tracking as tight as possible in order to
 489  * not miss-qualify lock contexts and miss possible deadlocks.
 490  */
 491
 492 static inline bool lockdep_softirq_start(void)
 493 {
 494         bool in_hardirq = false;
 495
 496         if (lockdep_hardirq_context()) {
 497                 in_hardirq = true;
 498                 lockdep_hardirq_exit();
 499         }
 500
 501         lockdep_softirq_enter();
 502
 503         return in_hardirq;
 504 }
 505
 506 static inline void lockdep_softirq_end(bool in_hardirq)
 507 {
 508         lockdep_softirq_exit();
 509
 510         if (in_hardirq)
 511                 lockdep_hardirq_enter();
 512 }
 513 #else
 514 static inline bool lockdep_softirq_start(void) { return false; }
 515 static inline void lockdep_softirq_end(bool in_hardirq) { }
 516 #endif
 517
 518 static void handle_softirqs(bool ksirqd)
 519 {
 520         unsigned long end = jiffies + MAX_SOFTIRQ_TIME;
 521         unsigned long old_flags = current->flags;
 522         int max_restart = MAX_SOFTIRQ_RESTART;
 523         struct softirq_action *h;
 524         bool in_hardirq;
 525         __u32 pending;
 526         int softirq_bit;
 527
 528         /*
 529          * Mask out PF_MEMALLOC as the current task context is borrowed for the
 530          * softirq. A softirq handled, such as network RX, might set PF_MEMALLOC
 531          * again if the socket is related to swapping.
 532          */
 533         current->flags &= ~PF_MEMALLOC;
 534
 535         pending = local_softirq_pending();
 536
 537         softirq_handle_begin();
 538         in_hardirq = lockdep_softirq_start();
 539         account_softirq_enter(current);
 540
 541 restart:
 542         /* Reset the pending bitmask before enabling irqs */
 543         set_softirq_pending(0);
 544
 545         local_irq_enable();
 546
 547         h = softirq_vec;
 548
 549         while ((softirq_bit = ffs(pending))) {
 550                 unsigned int vec_nr;
 551                 int prev_count;
 552
 553                 h += softirq_bit - 1;
 554
 555                 vec_nr = h - softirq_vec;
 556                 prev_count = preempt_count();
 557
 558                 kstat_incr_softirqs_this_cpu(vec_nr);
 559
 560                 trace_softirq_entry(vec_nr);
 561                 h->action();
 562                 trace_softirq_exit(vec_nr);
 563                 if (unlikely(prev_count != preempt_count())) {
 564                         pr_err("huh, entered softirq %u %s %p with preempt_count %08x, exited with %08x?\n",
 565                                vec_nr, softirq_to_name[vec_nr], h->action,
 566                                prev_count, preempt_count());
 567                         preempt_count_set(prev_count);
 568                 }
 569                 h++;
 570                 pending >>= softirq_bit;
 571         }
 572
 573         if (!IS_ENABLED(CONFIG_PREEMPT_RT) && ksirqd)
 574                 rcu_softirq_qs();
 575
 576         local_irq_disable();
 577
 578         pending = local_softirq_pending();
 579         if (pending) {
 580                 if (time_before(jiffies, end) && !need_resched() &&
 581                     --max_restart)
 582                         goto restart;
 583
 584                 wakeup_softirqd();
 585         }
 586
 587         account_softirq_exit(current);
 588         lockdep_softirq_end(in_hardirq);
 589         softirq_handle_end();
 590         current_restore_flags(old_flags, PF_MEMALLOC);
 591 }
 592
 593 asmlinkage __visible void __softirq_entry __do_softirq(void)
 594 {
 595         handle_softirqs(false);
 596 }
 597
 598 /**
 599  * irq_enter_rcu - Enter an interrupt context with RCU watching
 600  */
 601 void irq_enter_rcu(void)
 602 {
 603         __irq_enter_raw();
 604
 605         if (tick_nohz_full_cpu(smp_processor_id()) ||
 606             (is_idle_task(current) && (irq_count() == HARDIRQ_OFFSET)))
 607                 tick_irq_enter();
 608
 609         account_hardirq_enter(current);
 610 }
 611
 612 /**
 613  * irq_enter - Enter an interrupt context including RCU update
 614  */
 615 void irq_enter(void)
 616 {
 617         ct_irq_enter();
 618         irq_enter_rcu();
 619 }
 620
 621 static inline void tick_irq_exit(void)
 622 {
 623 #ifdef CONFIG_NO_HZ_COMMON
 624         int cpu = smp_processor_id();
 625
 626         /* Make sure that timer wheel updates are propagated */
 627         if ((sched_core_idle_cpu(cpu) && !need_resched()) || tick_nohz_full_cpu(cpu)) {
 628                 if (!in_hardirq())
 629                         tick_nohz_irq_exit();
 630         }
 631 #endif
 632 }
 633
 634 #ifdef CONFIG_IRQ_FORCED_THREADING
 635 DEFINE_PER_CPU(struct task_struct *, ktimerd);
 636 DEFINE_PER_CPU(unsigned long, pending_timer_softirq);
 637
 638 static void wake_timersd(void)
 639 {
 640         struct task_struct *tsk = __this_cpu_read(ktimerd);
 641
 642         if (tsk)
 643                 wake_up_process(tsk);
 644 }
 645
 646 #else
 647
 648 static inline void wake_timersd(void) { }
 649
 650 #endif
 651
 652 static inline void __irq_exit_rcu(void)
 653 {
 654 #ifndef __ARCH_IRQ_EXIT_IRQS_DISABLED
 655         local_irq_disable();
 656 #else
 657         lockdep_assert_irqs_disabled();
 658 #endif
 659         account_hardirq_exit(current);
 660         preempt_count_sub(HARDIRQ_OFFSET);
 661         if (!in_interrupt() && local_softirq_pending())
 662                 invoke_softirq();
 663
 664         if (IS_ENABLED(CONFIG_IRQ_FORCED_THREADING) && force_irqthreads() &&
 665             local_timers_pending_force_th() && !(in_nmi() | in_hardirq()))
 666                 wake_timersd();
 667
 668         tick_irq_exit();
 669 }
 670
 671 /**
 672  * irq_exit_rcu() - Exit an interrupt context without updating RCU
 673  *
 674  * Also processes softirqs if needed and possible.
 675  */
 676 void irq_exit_rcu(void)
 677 {
 678         __irq_exit_rcu();
 679          /* must be last! */
 680         lockdep_hardirq_exit();
 681 }
 682
 683 /**
 684  * irq_exit - Exit an interrupt context, update RCU and lockdep
 685  *
 686  * Also processes softirqs if needed and possible.
 687  */
 688 void irq_exit(void)
 689 {
 690         __irq_exit_rcu();
 691         ct_irq_exit();
 692          /* must be last! */
 693         lockdep_hardirq_exit();
 694 }
 695
 696 /*
 697  * This function must run with irqs disabled!
 698  */
 699 inline void raise_softirq_irqoff(unsigned int nr)
 700 {
 701         __raise_softirq_irqoff(nr);
 702
 703         /*
 704          * If we're in an interrupt or softirq, we're done
 705          * (this also catches softirq-disabled code). We will
 706          * actually run the softirq once we return from
 707          * the irq or softirq.
 708          *
 709          * Otherwise we wake up ksoftirqd to make sure we
 710          * schedule the softirq soon.
 711          */
 712         if (!in_interrupt() && should_wake_ksoftirqd())
 713                 wakeup_softirqd();
 714 }
 715
 716 void raise_softirq(unsigned int nr)
 717 {
 718         unsigned long flags;
 719
 720         local_irq_save(flags);
 721         raise_softirq_irqoff(nr);
 722         local_irq_restore(flags);
 723 }
 724
 725 void __raise_softirq_irqoff(unsigned int nr)
 726 {
 727         lockdep_assert_irqs_disabled();
 728         trace_softirq_raise(nr);
 729         or_softirq_pending(1UL << nr);
 730 }
 731
 732 void open_softirq(int nr, void (*action)(void))
 733 {
 734         softirq_vec[nr].action = action;
 735 }
 736
 737 /*
 738  * Tasklets
 739  */
 740 struct tasklet_head {
 741         struct tasklet_struct *head;
 742         struct tasklet_struct **tail;
 743 };
 744
 745 static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec);
 746 static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec);
 747
 748 static void __tasklet_schedule_common(struct tasklet_struct *t,
 749                                       struct tasklet_head __percpu *headp,
 750                                       unsigned int softirq_nr)
 751 {
 752         struct tasklet_head *head;
 753         unsigned long flags;
 754
 755         local_irq_save(flags);
 756         head = this_cpu_ptr(headp);
 757         t->next = NULL;
 758         *head->tail = t;
 759         head->tail = &(t->next);
 760         raise_softirq_irqoff(softirq_nr);
 761         local_irq_restore(flags);
 762 }
 763
 764 void __tasklet_schedule(struct tasklet_struct *t)
 765 {
 766         __tasklet_schedule_common(t, &tasklet_vec,
 767                                   TASKLET_SOFTIRQ);
 768 }
 769 EXPORT_SYMBOL(__tasklet_schedule);
 770
 771 void __tasklet_hi_schedule(struct tasklet_struct *t)
 772 {
 773         __tasklet_schedule_common(t, &tasklet_hi_vec,
 774                                   HI_SOFTIRQ);
 775 }
 776 EXPORT_SYMBOL(__tasklet_hi_schedule);
 777
 778 static bool tasklet_clear_sched(struct tasklet_struct *t)
 779 {
 780         if (test_and_clear_wake_up_bit(TASKLET_STATE_SCHED, &t->state))
 781                 return true;
 782
 783         WARN_ONCE(1, "tasklet SCHED state not set: %s %pS\n",
 784                   t->use_callback ? "callback" : "func",
 785                   t->use_callback ? (void *)t->callback : (void *)t->func);
 786
 787         return false;
 788 }
 789
 790 static void tasklet_action_common(struct tasklet_head *tl_head,
 791                                   unsigned int softirq_nr)
 792 {
 793         struct tasklet_struct *list;
 794
 795         local_irq_disable();
 796         list = tl_head->head;
 797         tl_head->head = NULL;
 798         tl_head->tail = &tl_head->head;
 799         local_irq_enable();
 800
 801         while (list) {
 802                 struct tasklet_struct *t = list;
 803
 804                 list = list->next;
 805
 806                 if (tasklet_trylock(t)) {
 807                         if (!atomic_read(&t->count)) {
 808                                 if (tasklet_clear_sched(t)) {
 809                                         if (t->use_callback) {
 810                                                 trace_tasklet_entry(t, t->callback);
 811                                                 t->callback(t);
 812                                                 trace_tasklet_exit(t, t->callback);
 813                                         } else {
 814                                                 trace_tasklet_entry(t, t->func);
 815                                                 t->func(t->data);
 816                                                 trace_tasklet_exit(t, t->func);
 817                                         }
 818                                 }
 819                                 tasklet_unlock(t);
 820                                 continue;
 821                         }
 822                         tasklet_unlock(t);
 823                 }
 824
 825                 local_irq_disable();
 826                 t->next = NULL;
 827                 *tl_head->tail = t;
 828                 tl_head->tail = &t->next;
 829                 __raise_softirq_irqoff(softirq_nr);
 830                 local_irq_enable();
 831         }
 832 }
 833
 834 static __latent_entropy void tasklet_action(void)
 835 {
 836         workqueue_softirq_action(false);
 837         tasklet_action_common(this_cpu_ptr(&tasklet_vec), TASKLET_SOFTIRQ);
 838 }
 839
 840 static __latent_entropy void tasklet_hi_action(void)
 841 {
 842         workqueue_softirq_action(true);
 843         tasklet_action_common(this_cpu_ptr(&tasklet_hi_vec), HI_SOFTIRQ);
 844 }
 845
 846 void tasklet_setup(struct tasklet_struct *t,
 847                    void (*callback)(struct tasklet_struct *))
 848 {
 849         t->next = NULL;
 850         t->state = 0;
 851         atomic_set(&t->count, 0);
 852         t->callback = callback;
 853         t->use_callback = true;
 854         t->data = 0;
 855 }
 856 EXPORT_SYMBOL(tasklet_setup);
 857
 858 void tasklet_init(struct tasklet_struct *t,
 859                   void (*func)(unsigned long), unsigned long data)
 860 {
 861         t->next = NULL;
 862         t->state = 0;
 863         atomic_set(&t->count, 0);
 864         t->func = func;
 865         t->use_callback = false;
 866         t->data = data;
 867 }
 868 EXPORT_SYMBOL(tasklet_init);
 869
 870 #if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT)
 871 /*
 872  * Do not use in new code. Waiting for tasklets from atomic contexts is
 873  * error prone and should be avoided.
 874  */
 875 void tasklet_unlock_spin_wait(struct tasklet_struct *t)
 876 {
 877         while (test_bit(TASKLET_STATE_RUN, &(t)->state)) {
 878                 if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
 879                         /*
 880                          * Prevent a live lock when current preempted soft
 881                          * interrupt processing or prevents ksoftirqd from
 882                          * running. If the tasklet runs on a different CPU
 883                          * then this has no effect other than doing the BH
 884                          * disable/enable dance for nothing.
 885                          */
 886                         local_bh_disable();
 887                         local_bh_enable();
 888                 } else {
 889                         cpu_relax();
 890                 }
 891         }
 892 }
 893 EXPORT_SYMBOL(tasklet_unlock_spin_wait);
 894 #endif
 895
 896 void tasklet_kill(struct tasklet_struct *t)
 897 {
 898         if (in_interrupt())
 899                 pr_notice("Attempt to kill tasklet from interrupt\n");
 900
 901         wait_on_bit_lock(&t->state, TASKLET_STATE_SCHED, TASK_UNINTERRUPTIBLE);
 902
 903         tasklet_unlock_wait(t);
 904         tasklet_clear_sched(t);
 905 }
 906 EXPORT_SYMBOL(tasklet_kill);
 907
 908 #if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT)
 909 void tasklet_unlock(struct tasklet_struct *t)
 910 {
 911         clear_and_wake_up_bit(TASKLET_STATE_RUN, &t->state);
 912 }
 913 EXPORT_SYMBOL_GPL(tasklet_unlock);
 914
 915 void tasklet_unlock_wait(struct tasklet_struct *t)
 916 {
 917         wait_on_bit(&t->state, TASKLET_STATE_RUN, TASK_UNINTERRUPTIBLE);
 918 }
 919 EXPORT_SYMBOL_GPL(tasklet_unlock_wait);
 920 #endif
 921
 922 void __init softirq_init(void)
 923 {
 924         int cpu;
 925
 926         for_each_possible_cpu(cpu) {
 927                 per_cpu(tasklet_vec, cpu).tail =
 928                         &per_cpu(tasklet_vec, cpu).head;
 929                 per_cpu(tasklet_hi_vec, cpu).tail =
 930                         &per_cpu(tasklet_hi_vec, cpu).head;
 931         }
 932
 933         open_softirq(TASKLET_SOFTIRQ, tasklet_action);
 934         open_softirq(HI_SOFTIRQ, tasklet_hi_action);
 935 }
 936
 937 static int ksoftirqd_should_run(unsigned int cpu)
 938 {
 939         return local_softirq_pending();
 940 }
 941
 942 static void run_ksoftirqd(unsigned int cpu)
 943 {
 944         ksoftirqd_run_begin();
 945         if (local_softirq_pending()) {
 946                 /*
 947                  * We can safely run softirq on inline stack, as we are not deep
 948                  * in the task stack here.
 949                  */
 950                 handle_softirqs(true);
 951                 ksoftirqd_run_end();
 952                 cond_resched();
 953                 return;
 954         }
 955         ksoftirqd_run_end();
 956 }
 957
 958 #ifdef CONFIG_HOTPLUG_CPU
 959 static int takeover_tasklets(unsigned int cpu)
 960 {
 961         workqueue_softirq_dead(cpu);
 962
 963         /* CPU is dead, so no lock needed. */
 964         local_irq_disable();
 965
 966         /* Find end, append list for that CPU. */
 967         if (&per_cpu(tasklet_vec, cpu).head != per_cpu(tasklet_vec, cpu).tail) {
 968                 *__this_cpu_read(tasklet_vec.tail) = per_cpu(tasklet_vec, cpu).head;
 969                 __this_cpu_write(tasklet_vec.tail, per_cpu(tasklet_vec, cpu).tail);
 970                 per_cpu(tasklet_vec, cpu).head = NULL;
 971                 per_cpu(tasklet_vec, cpu).tail = &per_cpu(tasklet_vec, cpu).head;
 972         }
 973         raise_softirq_irqoff(TASKLET_SOFTIRQ);
 974
 975         if (&per_cpu(tasklet_hi_vec, cpu).head != per_cpu(tasklet_hi_vec, cpu).tail) {
 976                 *__this_cpu_read(tasklet_hi_vec.tail) = per_cpu(tasklet_hi_vec, cpu).head;
 977                 __this_cpu_write(tasklet_hi_vec.tail, per_cpu(tasklet_hi_vec, cpu).tail);
 978                 per_cpu(tasklet_hi_vec, cpu).head = NULL;
 979                 per_cpu(tasklet_hi_vec, cpu).tail = &per_cpu(tasklet_hi_vec, cpu).head;
 980         }
 981         raise_softirq_irqoff(HI_SOFTIRQ);
 982
 983         local_irq_enable();
 984         return 0;
 985 }
 986 #else
 987 #define takeover_tasklets       NULL
 988 #endif /* CONFIG_HOTPLUG_CPU */
 989
 990 static struct smp_hotplug_thread softirq_threads = {
 991         .store                  = &ksoftirqd,
 992         .thread_should_run      = ksoftirqd_should_run,
 993         .thread_fn              = run_ksoftirqd,
 994         .thread_comm            = "ksoftirqd/%u",
 995 };
 996
 997 #ifdef CONFIG_IRQ_FORCED_THREADING
 998 static void ktimerd_setup(unsigned int cpu)
 999 {
1000         /* Above SCHED_NORMAL to handle timers before regular tasks. */
1001         sched_set_fifo_low(current);
1002 }
1003
1004 static int ktimerd_should_run(unsigned int cpu)
1005 {
1006         return local_timers_pending_force_th();
1007 }
1008
1009 void raise_ktimers_thread(unsigned int nr)
1010 {
1011         trace_softirq_raise(nr);
1012         __this_cpu_or(pending_timer_softirq, BIT(nr));
1013 }
1014
1015 static void run_ktimerd(unsigned int cpu)
1016 {
1017         unsigned int timer_si;
1018
1019         ksoftirqd_run_begin();
1020
1021         timer_si = local_timers_pending_force_th();
1022         __this_cpu_write(pending_timer_softirq, 0);
1023         or_softirq_pending(timer_si);
1024
1025         __do_softirq();
1026
1027         ksoftirqd_run_end();
1028 }
1029
1030 static struct smp_hotplug_thread timer_thread = {
1031         .store                  = &ktimerd,
1032         .setup                  = ktimerd_setup,
1033         .thread_should_run      = ktimerd_should_run,
1034         .thread_fn              = run_ktimerd,
1035         .thread_comm            = "ktimers/%u",
1036 };
1037 #endif
1038
1039 static __init int spawn_ksoftirqd(void)
1040 {
1041         cpuhp_setup_state_nocalls(CPUHP_SOFTIRQ_DEAD, "softirq:dead", NULL,
1042                                   takeover_tasklets);
1043         BUG_ON(smpboot_register_percpu_thread(&softirq_threads));
1044 #ifdef CONFIG_IRQ_FORCED_THREADING
1045         if (force_irqthreads())
1046                 BUG_ON(smpboot_register_percpu_thread(&timer_thread));
1047 #endif
1048         return 0;
1049 }
1050 early_initcall(spawn_ksoftirqd);
1051
1052 /*
1053  * [ These __weak aliases are kept in a separate compilation unit, so that
1054  *   GCC does not inline them incorrectly. ]
1055  */
1056
1057 int __init __weak early_irq_init(void)
1058 {
1059         return 0;
1060 }
1061
1062 int __init __weak arch_probe_nr_irqs(void)
1063 {
1064         return NR_IRQS_LEGACY;
1065 }
1066
1067 int __init __weak arch_early_irq_init(void)
1068 {
1069         return 0;
1070 }
1071
1072 unsigned int __weak arch_dynirq_lower_bound(unsigned int from)
1073 {
1074         return from;
1075 }