File-copy from v4.4.100
This is the result of 'cp' from a linux-stable tree with the 'v4.4.100'
tag checked out (commit 26d6298789e695c9f627ce49a7bbd2286405798a) on
git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
Please refer to that tree for all history prior to this point.
Change-Id: I8a9ee2aea93cd29c52c847d0ce33091a73ae6afe
diff --git a/kernel/softirq.c b/kernel/softirq.c
new file mode 100644
index 0000000..479e443
--- /dev/null
+++ b/kernel/softirq.c
@@ -0,0 +1,787 @@
+/*
+ * linux/kernel/softirq.c
+ *
+ * Copyright (C) 1992 Linus Torvalds
+ *
+ * Distribute under GPLv2.
+ *
+ * Rewritten. Old one was good in 2.2, but in 2.3 it was immoral. --ANK (990903)
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/export.h>
+#include <linux/kernel_stat.h>
+#include <linux/interrupt.h>
+#include <linux/init.h>
+#include <linux/mm.h>
+#include <linux/notifier.h>
+#include <linux/percpu.h>
+#include <linux/cpu.h>
+#include <linux/freezer.h>
+#include <linux/kthread.h>
+#include <linux/rcupdate.h>
+#include <linux/ftrace.h>
+#include <linux/smp.h>
+#include <linux/smpboot.h>
+#include <linux/tick.h>
+#include <linux/irq.h>
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/irq.h>
+
+/*
+ - No shared variables, all the data are CPU local.
+ - If a softirq needs serialization, let it serialize itself
+ by its own spinlocks.
+ - Even if softirq is serialized, only local cpu is marked for
+ execution. Hence, we get something sort of weak cpu binding.
+ Though it is still not clear, will it result in better locality
+ or will not.
+
+ Examples:
+ - NET RX softirq. It is multithreaded and does not require
+ any global serialization.
+ - NET TX softirq. It kicks software netdevice queues, hence
+ it is logically serialized per device, but this serialization
+ is invisible to common code.
+ - Tasklets: serialized wrt itself.
+ */
+
+#ifndef __ARCH_IRQ_STAT
+irq_cpustat_t irq_stat[NR_CPUS] ____cacheline_aligned;
+EXPORT_SYMBOL(irq_stat);
+#endif
+
+static struct softirq_action softirq_vec[NR_SOFTIRQS] __cacheline_aligned_in_smp;
+
+DEFINE_PER_CPU(struct task_struct *, ksoftirqd);
+
+const char * const softirq_to_name[NR_SOFTIRQS] = {
+ "HI", "TIMER", "NET_TX", "NET_RX", "BLOCK", "BLOCK_IOPOLL",
+ "TASKLET", "SCHED", "HRTIMER", "RCU"
+};
+
+/*
+ * we cannot loop indefinitely here to avoid userspace starvation,
+ * but we also don't want to introduce a worst case 1/HZ latency
+ * to the pending events, so lets the scheduler to balance
+ * the softirq load for us.
+ */
+static void wakeup_softirqd(void)
+{
+ /* Interrupts are disabled: no need to stop preemption */
+ struct task_struct *tsk = __this_cpu_read(ksoftirqd);
+
+ if (tsk && tsk->state != TASK_RUNNING)
+ wake_up_process(tsk);
+}
+
+/*
+ * preempt_count and SOFTIRQ_OFFSET usage:
+ * - preempt_count is changed by SOFTIRQ_OFFSET on entering or leaving
+ * softirq processing.
+ * - preempt_count is changed by SOFTIRQ_DISABLE_OFFSET (= 2 * SOFTIRQ_OFFSET)
+ * on local_bh_disable or local_bh_enable.
+ * This lets us distinguish between whether we are currently processing
+ * softirq and whether we just have bh disabled.
+ */
+
+/*
+ * This one is for softirq.c-internal use,
+ * where hardirqs are disabled legitimately:
+ */
+#ifdef CONFIG_TRACE_IRQFLAGS
+void __local_bh_disable_ip(unsigned long ip, unsigned int cnt)
+{
+ unsigned long flags;
+
+ WARN_ON_ONCE(in_irq());
+
+ raw_local_irq_save(flags);
+ /*
+ * The preempt tracer hooks into preempt_count_add and will break
+ * lockdep because it calls back into lockdep after SOFTIRQ_OFFSET
+ * is set and before current->softirq_enabled is cleared.
+ * We must manually increment preempt_count here and manually
+ * call the trace_preempt_off later.
+ */
+ __preempt_count_add(cnt);
+ /*
+ * Were softirqs turned off above:
+ */
+ if (softirq_count() == (cnt & SOFTIRQ_MASK))
+ trace_softirqs_off(ip);
+ raw_local_irq_restore(flags);
+
+ if (preempt_count() == cnt) {
+#ifdef CONFIG_DEBUG_PREEMPT
+ current->preempt_disable_ip = get_parent_ip(CALLER_ADDR1);
+#endif
+ trace_preempt_off(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1));
+ }
+}
+EXPORT_SYMBOL(__local_bh_disable_ip);
+#endif /* CONFIG_TRACE_IRQFLAGS */
+
+static void __local_bh_enable(unsigned int cnt)
+{
+ WARN_ON_ONCE(!irqs_disabled());
+
+ if (softirq_count() == (cnt & SOFTIRQ_MASK))
+ trace_softirqs_on(_RET_IP_);
+ preempt_count_sub(cnt);
+}
+
+/*
+ * Special-case - softirqs can safely be enabled in
+ * cond_resched_softirq(), or by __do_softirq(),
+ * without processing still-pending softirqs:
+ */
+void _local_bh_enable(void)
+{
+ WARN_ON_ONCE(in_irq());
+ __local_bh_enable(SOFTIRQ_DISABLE_OFFSET);
+}
+EXPORT_SYMBOL(_local_bh_enable);
+
+void __local_bh_enable_ip(unsigned long ip, unsigned int cnt)
+{
+ WARN_ON_ONCE(in_irq() || irqs_disabled());
+#ifdef CONFIG_TRACE_IRQFLAGS
+ local_irq_disable();
+#endif
+ /*
+ * Are softirqs going to be turned on now:
+ */
+ if (softirq_count() == SOFTIRQ_DISABLE_OFFSET)
+ trace_softirqs_on(ip);
+ /*
+ * Keep preemption disabled until we are done with
+ * softirq processing:
+ */
+ preempt_count_sub(cnt - 1);
+
+ if (unlikely(!in_interrupt() && local_softirq_pending())) {
+ /*
+ * Run softirq if any pending. And do it in its own stack
+ * as we may be calling this deep in a task call stack already.
+ */
+ do_softirq();
+ }
+
+ preempt_count_dec();
+#ifdef CONFIG_TRACE_IRQFLAGS
+ local_irq_enable();
+#endif
+ preempt_check_resched();
+}
+EXPORT_SYMBOL(__local_bh_enable_ip);
+
+/*
+ * We restart softirq processing for at most MAX_SOFTIRQ_RESTART times,
+ * but break the loop if need_resched() is set or after 2 ms.
+ * The MAX_SOFTIRQ_TIME provides a nice upper bound in most cases, but in
+ * certain cases, such as stop_machine(), jiffies may cease to
+ * increment and so we need the MAX_SOFTIRQ_RESTART limit as
+ * well to make sure we eventually return from this method.
+ *
+ * These limits have been established via experimentation.
+ * The two things to balance is latency against fairness -
+ * we want to handle softirqs as soon as possible, but they
+ * should not be able to lock up the box.
+ */
+#define MAX_SOFTIRQ_TIME msecs_to_jiffies(2)
+#define MAX_SOFTIRQ_RESTART 10
+
+#ifdef CONFIG_TRACE_IRQFLAGS
+/*
+ * When we run softirqs from irq_exit() and thus on the hardirq stack we need
+ * to keep the lockdep irq context tracking as tight as possible in order to
+ * not miss-qualify lock contexts and miss possible deadlocks.
+ */
+
+static inline bool lockdep_softirq_start(void)
+{
+ bool in_hardirq = false;
+
+ if (trace_hardirq_context(current)) {
+ in_hardirq = true;
+ trace_hardirq_exit();
+ }
+
+ lockdep_softirq_enter();
+
+ return in_hardirq;
+}
+
+static inline void lockdep_softirq_end(bool in_hardirq)
+{
+ lockdep_softirq_exit();
+
+ if (in_hardirq)
+ trace_hardirq_enter();
+}
+#else
+static inline bool lockdep_softirq_start(void) { return false; }
+static inline void lockdep_softirq_end(bool in_hardirq) { }
+#endif
+
+asmlinkage __visible void __do_softirq(void)
+{
+ unsigned long end = jiffies + MAX_SOFTIRQ_TIME;
+ unsigned long old_flags = current->flags;
+ int max_restart = MAX_SOFTIRQ_RESTART;
+ struct softirq_action *h;
+ bool in_hardirq;
+ __u32 pending;
+ int softirq_bit;
+
+ /*
+ * Mask out PF_MEMALLOC s current task context is borrowed for the
+ * softirq. A softirq handled such as network RX might set PF_MEMALLOC
+ * again if the socket is related to swap
+ */
+ current->flags &= ~PF_MEMALLOC;
+
+ pending = local_softirq_pending();
+ account_irq_enter_time(current);
+
+ __local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET);
+ in_hardirq = lockdep_softirq_start();
+
+restart:
+ /* Reset the pending bitmask before enabling irqs */
+ set_softirq_pending(0);
+
+ local_irq_enable();
+
+ h = softirq_vec;
+
+ while ((softirq_bit = ffs(pending))) {
+ unsigned int vec_nr;
+ int prev_count;
+
+ h += softirq_bit - 1;
+
+ vec_nr = h - softirq_vec;
+ prev_count = preempt_count();
+
+ kstat_incr_softirqs_this_cpu(vec_nr);
+
+ trace_softirq_entry(vec_nr);
+ h->action(h);
+ trace_softirq_exit(vec_nr);
+ if (unlikely(prev_count != preempt_count())) {
+ pr_err("huh, entered softirq %u %s %p with preempt_count %08x, exited with %08x?\n",
+ vec_nr, softirq_to_name[vec_nr], h->action,
+ prev_count, preempt_count());
+ preempt_count_set(prev_count);
+ }
+ h++;
+ pending >>= softirq_bit;
+ }
+
+ rcu_bh_qs();
+ local_irq_disable();
+
+ pending = local_softirq_pending();
+ if (pending) {
+ if (time_before(jiffies, end) && !need_resched() &&
+ --max_restart)
+ goto restart;
+
+ wakeup_softirqd();
+ }
+
+ lockdep_softirq_end(in_hardirq);
+ account_irq_exit_time(current);
+ __local_bh_enable(SOFTIRQ_OFFSET);
+ WARN_ON_ONCE(in_interrupt());
+ tsk_restore_flags(current, old_flags, PF_MEMALLOC);
+}
+
+asmlinkage __visible void do_softirq(void)
+{
+ __u32 pending;
+ unsigned long flags;
+
+ if (in_interrupt())
+ return;
+
+ local_irq_save(flags);
+
+ pending = local_softirq_pending();
+
+ if (pending)
+ do_softirq_own_stack();
+
+ local_irq_restore(flags);
+}
+
+/*
+ * Enter an interrupt context.
+ */
+void irq_enter(void)
+{
+ rcu_irq_enter();
+ if (is_idle_task(current) && !in_interrupt()) {
+ /*
+ * Prevent raise_softirq from needlessly waking up ksoftirqd
+ * here, as softirq will be serviced on return from interrupt.
+ */
+ local_bh_disable();
+ tick_irq_enter();
+ _local_bh_enable();
+ }
+
+ __irq_enter();
+}
+
+static inline void invoke_softirq(void)
+{
+ if (!force_irqthreads) {
+#ifdef CONFIG_HAVE_IRQ_EXIT_ON_IRQ_STACK
+ /*
+ * We can safely execute softirq on the current stack if
+ * it is the irq stack, because it should be near empty
+ * at this stage.
+ */
+ __do_softirq();
+#else
+ /*
+ * Otherwise, irq_exit() is called on the task stack that can
+ * be potentially deep already. So call softirq in its own stack
+ * to prevent from any overrun.
+ */
+ do_softirq_own_stack();
+#endif
+ } else {
+ wakeup_softirqd();
+ }
+}
+
+static inline void tick_irq_exit(void)
+{
+#ifdef CONFIG_NO_HZ_COMMON
+ int cpu = smp_processor_id();
+
+ /* Make sure that timer wheel updates are propagated */
+ if ((idle_cpu(cpu) && !need_resched()) || tick_nohz_full_cpu(cpu)) {
+ if (!in_interrupt())
+ tick_nohz_irq_exit();
+ }
+#endif
+}
+
+/*
+ * Exit an interrupt context. Process softirqs if needed and possible:
+ */
+void irq_exit(void)
+{
+#ifndef __ARCH_IRQ_EXIT_IRQS_DISABLED
+ local_irq_disable();
+#else
+ WARN_ON_ONCE(!irqs_disabled());
+#endif
+
+ account_irq_exit_time(current);
+ preempt_count_sub(HARDIRQ_OFFSET);
+ if (!in_interrupt() && local_softirq_pending())
+ invoke_softirq();
+
+ tick_irq_exit();
+ rcu_irq_exit();
+ trace_hardirq_exit(); /* must be last! */
+}
+
+/*
+ * This function must run with irqs disabled!
+ */
+inline void raise_softirq_irqoff(unsigned int nr)
+{
+ __raise_softirq_irqoff(nr);
+
+ /*
+ * If we're in an interrupt or softirq, we're done
+ * (this also catches softirq-disabled code). We will
+ * actually run the softirq once we return from
+ * the irq or softirq.
+ *
+ * Otherwise we wake up ksoftirqd to make sure we
+ * schedule the softirq soon.
+ */
+ if (!in_interrupt())
+ wakeup_softirqd();
+}
+
+void raise_softirq(unsigned int nr)
+{
+ unsigned long flags;
+
+ local_irq_save(flags);
+ raise_softirq_irqoff(nr);
+ local_irq_restore(flags);
+}
+
+void __raise_softirq_irqoff(unsigned int nr)
+{
+ trace_softirq_raise(nr);
+ or_softirq_pending(1UL << nr);
+}
+
+void open_softirq(int nr, void (*action)(struct softirq_action *))
+{
+ softirq_vec[nr].action = action;
+}
+
+/*
+ * Tasklets
+ */
+struct tasklet_head {
+ struct tasklet_struct *head;
+ struct tasklet_struct **tail;
+};
+
+static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec);
+static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec);
+
+void __tasklet_schedule(struct tasklet_struct *t)
+{
+ unsigned long flags;
+
+ local_irq_save(flags);
+ t->next = NULL;
+ *__this_cpu_read(tasklet_vec.tail) = t;
+ __this_cpu_write(tasklet_vec.tail, &(t->next));
+ raise_softirq_irqoff(TASKLET_SOFTIRQ);
+ local_irq_restore(flags);
+}
+EXPORT_SYMBOL(__tasklet_schedule);
+
+void __tasklet_hi_schedule(struct tasklet_struct *t)
+{
+ unsigned long flags;
+
+ local_irq_save(flags);
+ t->next = NULL;
+ *__this_cpu_read(tasklet_hi_vec.tail) = t;
+ __this_cpu_write(tasklet_hi_vec.tail, &(t->next));
+ raise_softirq_irqoff(HI_SOFTIRQ);
+ local_irq_restore(flags);
+}
+EXPORT_SYMBOL(__tasklet_hi_schedule);
+
+void __tasklet_hi_schedule_first(struct tasklet_struct *t)
+{
+ BUG_ON(!irqs_disabled());
+
+ t->next = __this_cpu_read(tasklet_hi_vec.head);
+ __this_cpu_write(tasklet_hi_vec.head, t);
+ __raise_softirq_irqoff(HI_SOFTIRQ);
+}
+EXPORT_SYMBOL(__tasklet_hi_schedule_first);
+
+static void tasklet_action(struct softirq_action *a)
+{
+ struct tasklet_struct *list;
+
+ local_irq_disable();
+ list = __this_cpu_read(tasklet_vec.head);
+ __this_cpu_write(tasklet_vec.head, NULL);
+ __this_cpu_write(tasklet_vec.tail, this_cpu_ptr(&tasklet_vec.head));
+ local_irq_enable();
+
+ while (list) {
+ struct tasklet_struct *t = list;
+
+ list = list->next;
+
+ if (tasklet_trylock(t)) {
+ if (!atomic_read(&t->count)) {
+ if (!test_and_clear_bit(TASKLET_STATE_SCHED,
+ &t->state))
+ BUG();
+ t->func(t->data);
+ tasklet_unlock(t);
+ continue;
+ }
+ tasklet_unlock(t);
+ }
+
+ local_irq_disable();
+ t->next = NULL;
+ *__this_cpu_read(tasklet_vec.tail) = t;
+ __this_cpu_write(tasklet_vec.tail, &(t->next));
+ __raise_softirq_irqoff(TASKLET_SOFTIRQ);
+ local_irq_enable();
+ }
+}
+
+static void tasklet_hi_action(struct softirq_action *a)
+{
+ struct tasklet_struct *list;
+
+ local_irq_disable();
+ list = __this_cpu_read(tasklet_hi_vec.head);
+ __this_cpu_write(tasklet_hi_vec.head, NULL);
+ __this_cpu_write(tasklet_hi_vec.tail, this_cpu_ptr(&tasklet_hi_vec.head));
+ local_irq_enable();
+
+ while (list) {
+ struct tasklet_struct *t = list;
+
+ list = list->next;
+
+ if (tasklet_trylock(t)) {
+ if (!atomic_read(&t->count)) {
+ if (!test_and_clear_bit(TASKLET_STATE_SCHED,
+ &t->state))
+ BUG();
+ t->func(t->data);
+ tasklet_unlock(t);
+ continue;
+ }
+ tasklet_unlock(t);
+ }
+
+ local_irq_disable();
+ t->next = NULL;
+ *__this_cpu_read(tasklet_hi_vec.tail) = t;
+ __this_cpu_write(tasklet_hi_vec.tail, &(t->next));
+ __raise_softirq_irqoff(HI_SOFTIRQ);
+ local_irq_enable();
+ }
+}
+
+void tasklet_init(struct tasklet_struct *t,
+ void (*func)(unsigned long), unsigned long data)
+{
+ t->next = NULL;
+ t->state = 0;
+ atomic_set(&t->count, 0);
+ t->func = func;
+ t->data = data;
+}
+EXPORT_SYMBOL(tasklet_init);
+
+void tasklet_kill(struct tasklet_struct *t)
+{
+ if (in_interrupt())
+ pr_notice("Attempt to kill tasklet from interrupt\n");
+
+ while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) {
+ do {
+ yield();
+ } while (test_bit(TASKLET_STATE_SCHED, &t->state));
+ }
+ tasklet_unlock_wait(t);
+ clear_bit(TASKLET_STATE_SCHED, &t->state);
+}
+EXPORT_SYMBOL(tasklet_kill);
+
+/*
+ * tasklet_hrtimer
+ */
+
+/*
+ * The trampoline is called when the hrtimer expires. It schedules a tasklet
+ * to run __tasklet_hrtimer_trampoline() which in turn will call the intended
+ * hrtimer callback, but from softirq context.
+ */
+static enum hrtimer_restart __hrtimer_tasklet_trampoline(struct hrtimer *timer)
+{
+ struct tasklet_hrtimer *ttimer =
+ container_of(timer, struct tasklet_hrtimer, timer);
+
+ tasklet_hi_schedule(&ttimer->tasklet);
+ return HRTIMER_NORESTART;
+}
+
+/*
+ * Helper function which calls the hrtimer callback from
+ * tasklet/softirq context
+ */
+static void __tasklet_hrtimer_trampoline(unsigned long data)
+{
+ struct tasklet_hrtimer *ttimer = (void *)data;
+ enum hrtimer_restart restart;
+
+ restart = ttimer->function(&ttimer->timer);
+ if (restart != HRTIMER_NORESTART)
+ hrtimer_restart(&ttimer->timer);
+}
+
+/**
+ * tasklet_hrtimer_init - Init a tasklet/hrtimer combo for softirq callbacks
+ * @ttimer: tasklet_hrtimer which is initialized
+ * @function: hrtimer callback function which gets called from softirq context
+ * @which_clock: clock id (CLOCK_MONOTONIC/CLOCK_REALTIME)
+ * @mode: hrtimer mode (HRTIMER_MODE_ABS/HRTIMER_MODE_REL)
+ */
+void tasklet_hrtimer_init(struct tasklet_hrtimer *ttimer,
+ enum hrtimer_restart (*function)(struct hrtimer *),
+ clockid_t which_clock, enum hrtimer_mode mode)
+{
+ hrtimer_init(&ttimer->timer, which_clock, mode);
+ ttimer->timer.function = __hrtimer_tasklet_trampoline;
+ tasklet_init(&ttimer->tasklet, __tasklet_hrtimer_trampoline,
+ (unsigned long)ttimer);
+ ttimer->function = function;
+}
+EXPORT_SYMBOL_GPL(tasklet_hrtimer_init);
+
+void __init softirq_init(void)
+{
+ int cpu;
+
+ for_each_possible_cpu(cpu) {
+ per_cpu(tasklet_vec, cpu).tail =
+ &per_cpu(tasklet_vec, cpu).head;
+ per_cpu(tasklet_hi_vec, cpu).tail =
+ &per_cpu(tasklet_hi_vec, cpu).head;
+ }
+
+ open_softirq(TASKLET_SOFTIRQ, tasklet_action);
+ open_softirq(HI_SOFTIRQ, tasklet_hi_action);
+}
+
+static int ksoftirqd_should_run(unsigned int cpu)
+{
+ return local_softirq_pending();
+}
+
+static void run_ksoftirqd(unsigned int cpu)
+{
+ local_irq_disable();
+ if (local_softirq_pending()) {
+ /*
+ * We can safely run softirq on inline stack, as we are not deep
+ * in the task stack here.
+ */
+ __do_softirq();
+ local_irq_enable();
+ cond_resched_rcu_qs();
+ return;
+ }
+ local_irq_enable();
+}
+
+#ifdef CONFIG_HOTPLUG_CPU
+/*
+ * tasklet_kill_immediate is called to remove a tasklet which can already be
+ * scheduled for execution on @cpu.
+ *
+ * Unlike tasklet_kill, this function removes the tasklet
+ * _immediately_, even if the tasklet is in TASKLET_STATE_SCHED state.
+ *
+ * When this function is called, @cpu must be in the CPU_DEAD state.
+ */
+void tasklet_kill_immediate(struct tasklet_struct *t, unsigned int cpu)
+{
+ struct tasklet_struct **i;
+
+ BUG_ON(cpu_online(cpu));
+ BUG_ON(test_bit(TASKLET_STATE_RUN, &t->state));
+
+ if (!test_bit(TASKLET_STATE_SCHED, &t->state))
+ return;
+
+ /* CPU is dead, so no lock needed. */
+ for (i = &per_cpu(tasklet_vec, cpu).head; *i; i = &(*i)->next) {
+ if (*i == t) {
+ *i = t->next;
+ /* If this was the tail element, move the tail ptr */
+ if (*i == NULL)
+ per_cpu(tasklet_vec, cpu).tail = i;
+ return;
+ }
+ }
+ BUG();
+}
+
+static void takeover_tasklets(unsigned int cpu)
+{
+ /* CPU is dead, so no lock needed. */
+ local_irq_disable();
+
+ /* Find end, append list for that CPU. */
+ if (&per_cpu(tasklet_vec, cpu).head != per_cpu(tasklet_vec, cpu).tail) {
+ *__this_cpu_read(tasklet_vec.tail) = per_cpu(tasklet_vec, cpu).head;
+ this_cpu_write(tasklet_vec.tail, per_cpu(tasklet_vec, cpu).tail);
+ per_cpu(tasklet_vec, cpu).head = NULL;
+ per_cpu(tasklet_vec, cpu).tail = &per_cpu(tasklet_vec, cpu).head;
+ }
+ raise_softirq_irqoff(TASKLET_SOFTIRQ);
+
+ if (&per_cpu(tasklet_hi_vec, cpu).head != per_cpu(tasklet_hi_vec, cpu).tail) {
+ *__this_cpu_read(tasklet_hi_vec.tail) = per_cpu(tasklet_hi_vec, cpu).head;
+ __this_cpu_write(tasklet_hi_vec.tail, per_cpu(tasklet_hi_vec, cpu).tail);
+ per_cpu(tasklet_hi_vec, cpu).head = NULL;
+ per_cpu(tasklet_hi_vec, cpu).tail = &per_cpu(tasklet_hi_vec, cpu).head;
+ }
+ raise_softirq_irqoff(HI_SOFTIRQ);
+
+ local_irq_enable();
+}
+#endif /* CONFIG_HOTPLUG_CPU */
+
+static int cpu_callback(struct notifier_block *nfb, unsigned long action,
+ void *hcpu)
+{
+ switch (action) {
+#ifdef CONFIG_HOTPLUG_CPU
+ case CPU_DEAD:
+ case CPU_DEAD_FROZEN:
+ takeover_tasklets((unsigned long)hcpu);
+ break;
+#endif /* CONFIG_HOTPLUG_CPU */
+ }
+ return NOTIFY_OK;
+}
+
+static struct notifier_block cpu_nfb = {
+ .notifier_call = cpu_callback
+};
+
+static struct smp_hotplug_thread softirq_threads = {
+ .store = &ksoftirqd,
+ .thread_should_run = ksoftirqd_should_run,
+ .thread_fn = run_ksoftirqd,
+ .thread_comm = "ksoftirqd/%u",
+};
+
+static __init int spawn_ksoftirqd(void)
+{
+ register_cpu_notifier(&cpu_nfb);
+
+ BUG_ON(smpboot_register_percpu_thread(&softirq_threads));
+
+ return 0;
+}
+early_initcall(spawn_ksoftirqd);
+
+/*
+ * [ These __weak aliases are kept in a separate compilation unit, so that
+ * GCC does not inline them incorrectly. ]
+ */
+
+int __init __weak early_irq_init(void)
+{
+ return 0;
+}
+
+int __init __weak arch_probe_nr_irqs(void)
+{
+ return NR_IRQS_LEGACY;
+}
+
+int __init __weak arch_early_irq_init(void)
+{
+ return 0;
+}
+
+unsigned int __weak arch_dynirq_lower_bound(unsigned int from)
+{
+ return from;
+}