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
  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_irq());
 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 #else /* CONFIG_PREEMPT_RT */
 298
 299 /*
 300  * This one is for softirq.c-internal use, where hardirqs are disabled
 301  * legitimately:
 302  */
 303 #ifdef CONFIG_TRACE_IRQFLAGS
 304 void __local_bh_disable_ip(unsigned long ip, unsigned int cnt)
 305 {
 306         unsigned long flags;
 307
 308         WARN_ON_ONCE(in_irq());
 309
 310         raw_local_irq_save(flags);
 311         /*
 312          * The preempt tracer hooks into preempt_count_add and will break
 313          * lockdep because it calls back into lockdep after SOFTIRQ_OFFSET
 314          * is set and before current->softirq_enabled is cleared.
 315          * We must manually increment preempt_count here and manually
 316          * call the trace_preempt_off later.
 317          */
 318         __preempt_count_add(cnt);
 319         /*
 320          * Were softirqs turned off above:
 321          */
 322         if (softirq_count() == (cnt & SOFTIRQ_MASK))
 323                 lockdep_softirqs_off(ip);
 324         raw_local_irq_restore(flags);
 325
 326         if (preempt_count() == cnt) {
 327 #ifdef CONFIG_DEBUG_PREEMPT
 328                 current->preempt_disable_ip = get_lock_parent_ip();
 329 #endif
 330                 trace_preempt_off(CALLER_ADDR0, get_lock_parent_ip());
 331         }
 332 }
 333 EXPORT_SYMBOL(__local_bh_disable_ip);
 334 #endif /* CONFIG_TRACE_IRQFLAGS */
 335
 336 static void __local_bh_enable(unsigned int cnt)
 337 {
 338         lockdep_assert_irqs_disabled();
 339
 340         if (preempt_count() == cnt)
 341                 trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip());
 342
 343         if (softirq_count() == (cnt & SOFTIRQ_MASK))
 344                 lockdep_softirqs_on(_RET_IP_);
 345
 346         __preempt_count_sub(cnt);
 347 }
 348
 349 /*
 350  * Special-case - softirqs can safely be enabled by __do_softirq(),
 351  * without processing still-pending softirqs:
 352  */
 353 void _local_bh_enable(void)
 354 {
 355         WARN_ON_ONCE(in_irq());
 356         __local_bh_enable(SOFTIRQ_DISABLE_OFFSET);
 357 }
 358 EXPORT_SYMBOL(_local_bh_enable);
 359
 360 void __local_bh_enable_ip(unsigned long ip, unsigned int cnt)
 361 {
 362         WARN_ON_ONCE(in_irq());
 363         lockdep_assert_irqs_enabled();
 364 #ifdef CONFIG_TRACE_IRQFLAGS
 365         local_irq_disable();
 366 #endif
 367         /*
 368          * Are softirqs going to be turned on now:
 369          */
 370         if (softirq_count() == SOFTIRQ_DISABLE_OFFSET)
 371                 lockdep_softirqs_on(ip);
 372         /*
 373          * Keep preemption disabled until we are done with
 374          * softirq processing:
 375          */
 376         __preempt_count_sub(cnt - 1);
 377
 378         if (unlikely(!in_interrupt() && local_softirq_pending())) {
 379                 /*
 380                  * Run softirq if any pending. And do it in its own stack
 381                  * as we may be calling this deep in a task call stack already.
 382                  */
 383                 do_softirq();
 384         }
 385
 386         preempt_count_dec();
 387 #ifdef CONFIG_TRACE_IRQFLAGS
 388         local_irq_enable();
 389 #endif
 390         preempt_check_resched();
 391 }
 392 EXPORT_SYMBOL(__local_bh_enable_ip);
 393
 394 static inline void softirq_handle_begin(void)
 395 {
 396         __local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET);
 397 }
 398
 399 static inline void softirq_handle_end(void)
 400 {
 401         __local_bh_enable(SOFTIRQ_OFFSET);
 402         WARN_ON_ONCE(in_interrupt());
 403 }
 404
 405 static inline void ksoftirqd_run_begin(void)
 406 {
 407         local_irq_disable();
 408 }
 409
 410 static inline void ksoftirqd_run_end(void)
 411 {
 412         local_irq_enable();
 413 }
 414
 415 static inline bool should_wake_ksoftirqd(void)
 416 {
 417         return true;
 418 }
 419
 420 static inline void invoke_softirq(void)
 421 {
 422         if (ksoftirqd_running(local_softirq_pending()))
 423                 return;
 424
 425         if (!force_irqthreads() || !__this_cpu_read(ksoftirqd)) {
 426 #ifdef CONFIG_HAVE_IRQ_EXIT_ON_IRQ_STACK
 427                 /*
 428                  * We can safely execute softirq on the current stack if
 429                  * it is the irq stack, because it should be near empty
 430                  * at this stage.
 431                  */
 432                 __do_softirq();
 433 #else
 434                 /*
 435                  * Otherwise, irq_exit() is called on the task stack that can
 436                  * be potentially deep already. So call softirq in its own stack
 437                  * to prevent from any overrun.
 438                  */
 439                 do_softirq_own_stack();
 440 #endif
 441         } else {
 442                 wakeup_softirqd();
 443         }
 444 }
 445
 446 asmlinkage __visible void do_softirq(void)
 447 {
 448         __u32 pending;
 449         unsigned long flags;
 450
 451         if (in_interrupt())
 452                 return;
 453
 454         local_irq_save(flags);
 455
 456         pending = local_softirq_pending();
 457
 458         if (pending && !ksoftirqd_running(pending))
 459                 do_softirq_own_stack();
 460
 461         local_irq_restore(flags);
 462 }
 463
 464 #endif /* !CONFIG_PREEMPT_RT */
 465
 466 /*
 467  * We restart softirq processing for at most MAX_SOFTIRQ_RESTART times,
 468  * but break the loop if need_resched() is set or after 2 ms.
 469  * The MAX_SOFTIRQ_TIME provides a nice upper bound in most cases, but in
 470  * certain cases, such as stop_machine(), jiffies may cease to
 471  * increment and so we need the MAX_SOFTIRQ_RESTART limit as
 472  * well to make sure we eventually return from this method.
 473  *
 474  * These limits have been established via experimentation.
 475  * The two things to balance is latency against fairness -
 476  * we want to handle softirqs as soon as possible, but they
 477  * should not be able to lock up the box.
 478  */
 479 #define MAX_SOFTIRQ_TIME  msecs_to_jiffies(2)
 480 #define MAX_SOFTIRQ_RESTART 10
 481
 482 #ifdef CONFIG_TRACE_IRQFLAGS
 483 /*
 484  * When we run softirqs from irq_exit() and thus on the hardirq stack we need
 485  * to keep the lockdep irq context tracking as tight as possible in order to
 486  * not miss-qualify lock contexts and miss possible deadlocks.
 487  */
 488
 489 static inline bool lockdep_softirq_start(void)
 490 {
 491         bool in_hardirq = false;
 492
 493         if (lockdep_hardirq_context()) {
 494                 in_hardirq = true;
 495                 lockdep_hardirq_exit();
 496         }
 497
 498         lockdep_softirq_enter();
 499
 500         return in_hardirq;
 501 }
 502
 503 static inline void lockdep_softirq_end(bool in_hardirq)
 504 {
 505         lockdep_softirq_exit();
 506
 507         if (in_hardirq)
 508                 lockdep_hardirq_enter();
 509 }
 510 #else
 511 static inline bool lockdep_softirq_start(void) { return false; }
 512 static inline void lockdep_softirq_end(bool in_hardirq) { }
 513 #endif
 514
 515 asmlinkage __visible void __softirq_entry __do_softirq(void)
 516 {
 517         unsigned long end = jiffies + MAX_SOFTIRQ_TIME;
 518         unsigned long old_flags = current->flags;
 519         int max_restart = MAX_SOFTIRQ_RESTART;
 520         struct softirq_action *h;
 521         bool in_hardirq;
 522         __u32 pending;
 523         int softirq_bit;
 524
 525         /*
 526          * Mask out PF_MEMALLOC as the current task context is borrowed for the
 527          * softirq. A softirq handled, such as network RX, might set PF_MEMALLOC
 528          * again if the socket is related to swapping.
 529          */
 530         current->flags &= ~PF_MEMALLOC;
 531
 532         pending = local_softirq_pending();
 533
 534         softirq_handle_begin();
 535         in_hardirq = lockdep_softirq_start();
 536         account_softirq_enter(current);
 537
 538 restart:
 539         /* Reset the pending bitmask before enabling irqs */
 540         set_softirq_pending(0);
 541
 542         local_irq_enable();
 543
 544         h = softirq_vec;
 545
 546         while ((softirq_bit = ffs(pending))) {
 547                 unsigned int vec_nr;
 548                 int prev_count;
 549
 550                 h += softirq_bit - 1;
 551
 552                 vec_nr = h - softirq_vec;
 553                 prev_count = preempt_count();
 554
 555                 kstat_incr_softirqs_this_cpu(vec_nr);
 556
 557                 trace_softirq_entry(vec_nr);
 558                 h->action(h);
 559                 trace_softirq_exit(vec_nr);
 560                 if (unlikely(prev_count != preempt_count())) {
 561                         pr_err("huh, entered softirq %u %s %p with preempt_count %08x, exited with %08x?\n",
 562                                vec_nr, softirq_to_name[vec_nr], h->action,
 563                                prev_count, preempt_count());
 564                         preempt_count_set(prev_count);
 565                 }
 566                 h++;
 567                 pending >>= softirq_bit;
 568         }
 569
 570         if (!IS_ENABLED(CONFIG_PREEMPT_RT) &&
 571             __this_cpu_read(ksoftirqd) == current)
 572                 rcu_softirq_qs();
 573
 574         local_irq_disable();
 575
 576         pending = local_softirq_pending();
 577         if (pending) {
 578                 if (time_before(jiffies, end) && !need_resched() &&
 579                     --max_restart)
 580                         goto restart;
 581
 582                 wakeup_softirqd();
 583         }
 584
 585         account_softirq_exit(current);
 586         lockdep_softirq_end(in_hardirq);
 587         softirq_handle_end();
 588         current_restore_flags(old_flags, PF_MEMALLOC);
 589 }
 590
 591 /**
 592  * irq_enter_rcu - Enter an interrupt context with RCU watching
 593  */
 594 void irq_enter_rcu(void)
 595 {
 596         __irq_enter_raw();
 597
 598         if (tick_nohz_full_cpu(smp_processor_id()) ||
 599             (is_idle_task(current) && (irq_count() == HARDIRQ_OFFSET)))
 600                 tick_irq_enter();
 601
 602         account_hardirq_enter(current);
 603 }
 604
 605 /**
 606  * irq_enter - Enter an interrupt context including RCU update
 607  */
 608 void irq_enter(void)
 609 {
 610         rcu_irq_enter();
 611         irq_enter_rcu();
 612 }
 613
 614 static inline void tick_irq_exit(void)
 615 {
 616 #ifdef CONFIG_NO_HZ_COMMON
 617         int cpu = smp_processor_id();
 618
 619         /* Make sure that timer wheel updates are propagated */
 620         if ((idle_cpu(cpu) && !need_resched()) || tick_nohz_full_cpu(cpu)) {
 621                 if (!in_irq())
 622                         tick_nohz_irq_exit();
 623         }
 624 #endif
 625 }
 626
 627 static inline void __irq_exit_rcu(void)
 628 {
 629 #ifndef __ARCH_IRQ_EXIT_IRQS_DISABLED
 630         local_irq_disable();
 631 #else
 632         lockdep_assert_irqs_disabled();
 633 #endif
 634         account_hardirq_exit(current);
 635         preempt_count_sub(HARDIRQ_OFFSET);
 636         if (!in_interrupt() && local_softirq_pending())
 637                 invoke_softirq();
 638
 639         tick_irq_exit();
 640 }
 641
 642 /**
 643  * irq_exit_rcu() - Exit an interrupt context without updating RCU
 644  *
 645  * Also processes softirqs if needed and possible.
 646  */
 647 void irq_exit_rcu(void)
 648 {
 649         __irq_exit_rcu();
 650          /* must be last! */
 651         lockdep_hardirq_exit();
 652 }
 653
 654 /**
 655  * irq_exit - Exit an interrupt context, update RCU and lockdep
 656  *
 657  * Also processes softirqs if needed and possible.
 658  */
 659 void irq_exit(void)
 660 {
 661         __irq_exit_rcu();
 662         rcu_irq_exit();
 663          /* must be last! */
 664         lockdep_hardirq_exit();
 665 }
 666
 667 /*
 668  * This function must run with irqs disabled!
 669  */
 670 inline void raise_softirq_irqoff(unsigned int nr)
 671 {
 672         __raise_softirq_irqoff(nr);
 673
 674         /*
 675          * If we're in an interrupt or softirq, we're done
 676          * (this also catches softirq-disabled code). We will
 677          * actually run the softirq once we return from
 678          * the irq or softirq.
 679          *
 680          * Otherwise we wake up ksoftirqd to make sure we
 681          * schedule the softirq soon.
 682          */
 683         if (!in_interrupt() && should_wake_ksoftirqd())
 684                 wakeup_softirqd();
 685 }
 686
 687 void raise_softirq(unsigned int nr)
 688 {
 689         unsigned long flags;
 690
 691         local_irq_save(flags);
 692         raise_softirq_irqoff(nr);
 693         local_irq_restore(flags);
 694 }
 695
 696 void __raise_softirq_irqoff(unsigned int nr)
 697 {
 698         lockdep_assert_irqs_disabled();
 699         trace_softirq_raise(nr);
 700         or_softirq_pending(1UL << nr);
 701 }
 702
 703 void open_softirq(int nr, void (*action)(struct softirq_action *))
 704 {
 705         softirq_vec[nr].action = action;
 706 }
 707
 708 /*
 709  * Tasklets
 710  */
 711 struct tasklet_head {
 712         struct tasklet_struct *head;
 713         struct tasklet_struct **tail;
 714 };
 715
 716 static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec);
 717 static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec);
 718
 719 static void __tasklet_schedule_common(struct tasklet_struct *t,
 720                                       struct tasklet_head __percpu *headp,
 721                                       unsigned int softirq_nr)
 722 {
 723         struct tasklet_head *head;
 724         unsigned long flags;
 725
 726         local_irq_save(flags);
 727         head = this_cpu_ptr(headp);
 728         t->next = NULL;
 729         *head->tail = t;
 730         head->tail = &(t->next);
 731         raise_softirq_irqoff(softirq_nr);
 732         local_irq_restore(flags);
 733 }
 734
 735 void __tasklet_schedule(struct tasklet_struct *t)
 736 {
 737         __tasklet_schedule_common(t, &tasklet_vec,
 738                                   TASKLET_SOFTIRQ);
 739 }
 740 EXPORT_SYMBOL(__tasklet_schedule);
 741
 742 void __tasklet_hi_schedule(struct tasklet_struct *t)
 743 {
 744         __tasklet_schedule_common(t, &tasklet_hi_vec,
 745                                   HI_SOFTIRQ);
 746 }
 747 EXPORT_SYMBOL(__tasklet_hi_schedule);
 748
 749 static bool tasklet_clear_sched(struct tasklet_struct *t)
 750 {
 751         if (test_and_clear_bit(TASKLET_STATE_SCHED, &t->state)) {
 752                 wake_up_var(&t->state);
 753                 return true;
 754         }
 755
 756         WARN_ONCE(1, "tasklet SCHED state not set: %s %pS\n",
 757                   t->use_callback ? "callback" : "func",
 758                   t->use_callback ? (void *)t->callback : (void *)t->func);
 759
 760         return false;
 761 }
 762
 763 static void tasklet_action_common(struct softirq_action *a,
 764                                   struct tasklet_head *tl_head,
 765                                   unsigned int softirq_nr)
 766 {
 767         struct tasklet_struct *list;
 768
 769         local_irq_disable();
 770         list = tl_head->head;
 771         tl_head->head = NULL;
 772         tl_head->tail = &tl_head->head;
 773         local_irq_enable();
 774
 775         while (list) {
 776                 struct tasklet_struct *t = list;
 777
 778                 list = list->next;
 779
 780                 if (tasklet_trylock(t)) {
 781                         if (!atomic_read(&t->count)) {
 782                                 if (tasklet_clear_sched(t)) {
 783                                         if (t->use_callback)
 784                                                 t->callback(t);
 785                                         else
 786                                                 t->func(t->data);
 787                                 }
 788                                 tasklet_unlock(t);
 789                                 continue;
 790                         }
 791                         tasklet_unlock(t);
 792                 }
 793
 794                 local_irq_disable();
 795                 t->next = NULL;
 796                 *tl_head->tail = t;
 797                 tl_head->tail = &t->next;
 798                 __raise_softirq_irqoff(softirq_nr);
 799                 local_irq_enable();
 800         }
 801 }
 802
 803 static __latent_entropy void tasklet_action(struct softirq_action *a)
 804 {
 805         tasklet_action_common(a, this_cpu_ptr(&tasklet_vec), TASKLET_SOFTIRQ);
 806 }
 807
 808 static __latent_entropy void tasklet_hi_action(struct softirq_action *a)
 809 {
 810         tasklet_action_common(a, this_cpu_ptr(&tasklet_hi_vec), HI_SOFTIRQ);
 811 }
 812
 813 void tasklet_setup(struct tasklet_struct *t,
 814                    void (*callback)(struct tasklet_struct *))
 815 {
 816         t->next = NULL;
 817         t->state = 0;
 818         atomic_set(&t->count, 0);
 819         t->callback = callback;
 820         t->use_callback = true;
 821         t->data = 0;
 822 }
 823 EXPORT_SYMBOL(tasklet_setup);
 824
 825 void tasklet_init(struct tasklet_struct *t,
 826                   void (*func)(unsigned long), unsigned long data)
 827 {
 828         t->next = NULL;
 829         t->state = 0;
 830         atomic_set(&t->count, 0);
 831         t->func = func;
 832         t->use_callback = false;
 833         t->data = data;
 834 }
 835 EXPORT_SYMBOL(tasklet_init);
 836
 837 #if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT)
 838 /*
 839  * Do not use in new code. Waiting for tasklets from atomic contexts is
 840  * error prone and should be avoided.
 841  */
 842 void tasklet_unlock_spin_wait(struct tasklet_struct *t)
 843 {
 844         while (test_bit(TASKLET_STATE_RUN, &(t)->state)) {
 845                 if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
 846                         /*
 847                          * Prevent a live lock when current preempted soft
 848                          * interrupt processing or prevents ksoftirqd from
 849                          * running. If the tasklet runs on a different CPU
 850                          * then this has no effect other than doing the BH
 851                          * disable/enable dance for nothing.
 852                          */
 853                         local_bh_disable();
 854                         local_bh_enable();
 855                 } else {
 856                         cpu_relax();
 857                 }
 858         }
 859 }
 860 EXPORT_SYMBOL(tasklet_unlock_spin_wait);
 861 #endif
 862
 863 void tasklet_kill(struct tasklet_struct *t)
 864 {
 865         if (in_interrupt())
 866                 pr_notice("Attempt to kill tasklet from interrupt\n");
 867
 868         while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state))
 869                 wait_var_event(&t->state, !test_bit(TASKLET_STATE_SCHED, &t->state));
 870
 871         tasklet_unlock_wait(t);
 872         tasklet_clear_sched(t);
 873 }
 874 EXPORT_SYMBOL(tasklet_kill);
 875
 876 #if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT)
 877 void tasklet_unlock(struct tasklet_struct *t)
 878 {
 879         smp_mb__before_atomic();
 880         clear_bit(TASKLET_STATE_RUN, &t->state);
 881         smp_mb__after_atomic();
 882         wake_up_var(&t->state);
 883 }
 884 EXPORT_SYMBOL_GPL(tasklet_unlock);
 885
 886 void tasklet_unlock_wait(struct tasklet_struct *t)
 887 {
 888         wait_var_event(&t->state, !test_bit(TASKLET_STATE_RUN, &t->state));
 889 }
 890 EXPORT_SYMBOL_GPL(tasklet_unlock_wait);
 891 #endif
 892
 893 void __init softirq_init(void)
 894 {
 895         int cpu;
 896
 897         for_each_possible_cpu(cpu) {
 898                 per_cpu(tasklet_vec, cpu).tail =
 899                         &per_cpu(tasklet_vec, cpu).head;
 900                 per_cpu(tasklet_hi_vec, cpu).tail =
 901                         &per_cpu(tasklet_hi_vec, cpu).head;
 902         }
 903
 904         open_softirq(TASKLET_SOFTIRQ, tasklet_action);
 905         open_softirq(HI_SOFTIRQ, tasklet_hi_action);
 906 }
 907
 908 static int ksoftirqd_should_run(unsigned int cpu)
 909 {
 910         return local_softirq_pending();
 911 }
 912
 913 static void run_ksoftirqd(unsigned int cpu)
 914 {
 915         ksoftirqd_run_begin();
 916         if (local_softirq_pending()) {
 917                 /*
 918                  * We can safely run softirq on inline stack, as we are not deep
 919                  * in the task stack here.
 920                  */
 921                 __do_softirq();
 922                 ksoftirqd_run_end();
 923                 cond_resched();
 924                 return;
 925         }
 926         ksoftirqd_run_end();
 927 }
 928
 929 #ifdef CONFIG_HOTPLUG_CPU
 930 static int takeover_tasklets(unsigned int cpu)
 931 {
 932         /* CPU is dead, so no lock needed. */
 933         local_irq_disable();
 934
 935         /* Find end, append list for that CPU. */
 936         if (&per_cpu(tasklet_vec, cpu).head != per_cpu(tasklet_vec, cpu).tail) {
 937                 *__this_cpu_read(tasklet_vec.tail) = per_cpu(tasklet_vec, cpu).head;
 938                 __this_cpu_write(tasklet_vec.tail, per_cpu(tasklet_vec, cpu).tail);
 939                 per_cpu(tasklet_vec, cpu).head = NULL;
 940                 per_cpu(tasklet_vec, cpu).tail = &per_cpu(tasklet_vec, cpu).head;
 941         }
 942         raise_softirq_irqoff(TASKLET_SOFTIRQ);
 943
 944         if (&per_cpu(tasklet_hi_vec, cpu).head != per_cpu(tasklet_hi_vec, cpu).tail) {
 945                 *__this_cpu_read(tasklet_hi_vec.tail) = per_cpu(tasklet_hi_vec, cpu).head;
 946                 __this_cpu_write(tasklet_hi_vec.tail, per_cpu(tasklet_hi_vec, cpu).tail);
 947                 per_cpu(tasklet_hi_vec, cpu).head = NULL;
 948                 per_cpu(tasklet_hi_vec, cpu).tail = &per_cpu(tasklet_hi_vec, cpu).head;
 949         }
 950         raise_softirq_irqoff(HI_SOFTIRQ);
 951
 952         local_irq_enable();
 953         return 0;
 954 }
 955 #else
 956 #define takeover_tasklets       NULL
 957 #endif /* CONFIG_HOTPLUG_CPU */
 958
 959 static struct smp_hotplug_thread softirq_threads = {
 960         .store                  = &ksoftirqd,
 961         .thread_should_run      = ksoftirqd_should_run,
 962         .thread_fn              = run_ksoftirqd,
 963         .thread_comm            = "ksoftirqd/%u",
 964 };
 965
 966 static __init int spawn_ksoftirqd(void)
 967 {
 968         cpuhp_setup_state_nocalls(CPUHP_SOFTIRQ_DEAD, "softirq:dead", NULL,
 969                                   takeover_tasklets);
 970         BUG_ON(smpboot_register_percpu_thread(&softirq_threads));
 971
 972         return 0;
 973 }
 974 early_initcall(spawn_ksoftirqd);
 975
 976 /*
 977  * [ These __weak aliases are kept in a separate compilation unit, so that
 978  *   GCC does not inline them incorrectly. ]
 979  */
 980
 981 int __init __weak early_irq_init(void)
 982 {
 983         return 0;
 984 }
 985
 986 int __init __weak arch_probe_nr_irqs(void)
 987 {
 988         return NR_IRQS_LEGACY;
 989 }
 990
 991 int __init __weak arch_early_irq_init(void)
 992 {
 993         return 0;
 994 }
 995
 996 unsigned int __weak arch_dynirq_lower_bound(unsigned int from)
 997 {
 998         return from;
 999 }