diff options
Diffstat (limited to 'kernel/softirq.c')
| -rw-r--r-- | kernel/softirq.c | 999 |
1 files changed, 999 insertions, 0 deletions
diff --git a/kernel/softirq.c b/kernel/softirq.c new file mode 100644 index 0000000000..210cf5f8d9 --- /dev/null +++ b/kernel/softirq.c @@ -0,0 +1,999 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * linux/kernel/softirq.c + * + * Copyright (C) 1992 Linus Torvalds + * + * 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/local_lock.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> +#include <linux/wait_bit.h> + +#include <asm/softirq_stack.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 +DEFINE_PER_CPU_ALIGNED(irq_cpustat_t, irq_stat); +EXPORT_PER_CPU_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", "IRQ_POLL", + "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) + wake_up_process(tsk); +} + +#ifdef CONFIG_TRACE_IRQFLAGS +DEFINE_PER_CPU(int, hardirqs_enabled); +DEFINE_PER_CPU(int, hardirq_context); +EXPORT_PER_CPU_SYMBOL_GPL(hardirqs_enabled); +EXPORT_PER_CPU_SYMBOL_GPL(hardirq_context); +#endif + +/* + * SOFTIRQ_OFFSET usage: + * + * On !RT kernels 'count' is the preempt counter, on RT kernels this applies + * to a per CPU counter and to task::softirqs_disabled_cnt. + * + * - count is changed by SOFTIRQ_OFFSET on entering or leaving softirq + * processing. + * + * - 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. + */ +#ifdef CONFIG_PREEMPT_RT + +/* + * RT accounts for BH disabled sections in task::softirqs_disabled_cnt and + * also in per CPU softirq_ctrl::cnt. This is necessary to allow tasks in a + * softirq disabled section to be preempted. + * + * The per task counter is used for softirq_count(), in_softirq() and + * in_serving_softirqs() because these counts are only valid when the task + * holding softirq_ctrl::lock is running. + * + * The per CPU counter prevents pointless wakeups of ksoftirqd in case that + * the task which is in a softirq disabled section is preempted or blocks. + */ +struct softirq_ctrl { + local_lock_t lock; + int cnt; +}; + +static DEFINE_PER_CPU(struct softirq_ctrl, softirq_ctrl) = { + .lock = INIT_LOCAL_LOCK(softirq_ctrl.lock), +}; + +/** + * local_bh_blocked() - Check for idle whether BH processing is blocked + * + * Returns false if the per CPU softirq::cnt is 0 otherwise true. + * + * This is invoked from the idle task to guard against false positive + * softirq pending warnings, which would happen when the task which holds + * softirq_ctrl::lock was the only running task on the CPU and blocks on + * some other lock. + */ +bool local_bh_blocked(void) +{ + return __this_cpu_read(softirq_ctrl.cnt) != 0; +} + +void __local_bh_disable_ip(unsigned long ip, unsigned int cnt) +{ + unsigned long flags; + int newcnt; + + WARN_ON_ONCE(in_hardirq()); + + /* First entry of a task into a BH disabled section? */ + if (!current->softirq_disable_cnt) { + if (preemptible()) { + local_lock(&softirq_ctrl.lock); + /* Required to meet the RCU bottomhalf requirements. */ + rcu_read_lock(); + } else { + DEBUG_LOCKS_WARN_ON(this_cpu_read(softirq_ctrl.cnt)); + } + } + + /* + * Track the per CPU softirq disabled state. On RT this is per CPU + * state to allow preemption of bottom half disabled sections. + */ + newcnt = __this_cpu_add_return(softirq_ctrl.cnt, cnt); + /* + * Reflect the result in the task state to prevent recursion on the + * local lock and to make softirq_count() & al work. + */ + current->softirq_disable_cnt = newcnt; + + if (IS_ENABLED(CONFIG_TRACE_IRQFLAGS) && newcnt == cnt) { + raw_local_irq_save(flags); + lockdep_softirqs_off(ip); + raw_local_irq_restore(flags); + } +} +EXPORT_SYMBOL(__local_bh_disable_ip); + +static void __local_bh_enable(unsigned int cnt, bool unlock) +{ + unsigned long flags; + int newcnt; + + DEBUG_LOCKS_WARN_ON(current->softirq_disable_cnt != + this_cpu_read(softirq_ctrl.cnt)); + + if (IS_ENABLED(CONFIG_TRACE_IRQFLAGS) && softirq_count() == cnt) { + raw_local_irq_save(flags); + lockdep_softirqs_on(_RET_IP_); + raw_local_irq_restore(flags); + } + + newcnt = __this_cpu_sub_return(softirq_ctrl.cnt, cnt); + current->softirq_disable_cnt = newcnt; + + if (!newcnt && unlock) { + rcu_read_unlock(); + local_unlock(&softirq_ctrl.lock); + } +} + +void __local_bh_enable_ip(unsigned long ip, unsigned int cnt) +{ + bool preempt_on = preemptible(); + unsigned long flags; + u32 pending; + int curcnt; + + WARN_ON_ONCE(in_hardirq()); + lockdep_assert_irqs_enabled(); + + local_irq_save(flags); + curcnt = __this_cpu_read(softirq_ctrl.cnt); + + /* + * If this is not reenabling soft interrupts, no point in trying to + * run pending ones. + */ + if (curcnt != cnt) + goto out; + + pending = local_softirq_pending(); + if (!pending) + goto out; + + /* + * If this was called from non preemptible context, wake up the + * softirq daemon. + */ + if (!preempt_on) { + wakeup_softirqd(); + goto out; + } + + /* + * Adjust softirq count to SOFTIRQ_OFFSET which makes + * in_serving_softirq() become true. + */ + cnt = SOFTIRQ_OFFSET; + __local_bh_enable(cnt, false); + __do_softirq(); + +out: + __local_bh_enable(cnt, preempt_on); + local_irq_restore(flags); +} +EXPORT_SYMBOL(__local_bh_enable_ip); + +/* + * Invoked from ksoftirqd_run() outside of the interrupt disabled section + * to acquire the per CPU local lock for reentrancy protection. + */ +static inline void ksoftirqd_run_begin(void) +{ + __local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET); + local_irq_disable(); +} + +/* Counterpart to ksoftirqd_run_begin() */ +static inline void ksoftirqd_run_end(void) +{ + __local_bh_enable(SOFTIRQ_OFFSET, true); + WARN_ON_ONCE(in_interrupt()); + local_irq_enable(); +} + +static inline void softirq_handle_begin(void) { } +static inline void softirq_handle_end(void) { } + +static inline bool should_wake_ksoftirqd(void) +{ + return !this_cpu_read(softirq_ctrl.cnt); +} + +static inline void invoke_softirq(void) +{ + if (should_wake_ksoftirqd()) + wakeup_softirqd(); +} + +/* + * flush_smp_call_function_queue() can raise a soft interrupt in a function + * call. On RT kernels this is undesired and the only known functionality + * in the block layer which does this is disabled on RT. If soft interrupts + * get raised which haven't been raised before the flush, warn so it can be + * investigated. + */ +void do_softirq_post_smp_call_flush(unsigned int was_pending) +{ + if (WARN_ON_ONCE(was_pending != local_softirq_pending())) + invoke_softirq(); +} + +#else /* CONFIG_PREEMPT_RT */ + +/* + * 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_hardirq()); + + 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)) + lockdep_softirqs_off(ip); + raw_local_irq_restore(flags); + + if (preempt_count() == cnt) { +#ifdef CONFIG_DEBUG_PREEMPT + current->preempt_disable_ip = get_lock_parent_ip(); +#endif + trace_preempt_off(CALLER_ADDR0, get_lock_parent_ip()); + } +} +EXPORT_SYMBOL(__local_bh_disable_ip); +#endif /* CONFIG_TRACE_IRQFLAGS */ + +static void __local_bh_enable(unsigned int cnt) +{ + lockdep_assert_irqs_disabled(); + + if (preempt_count() == cnt) + trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip()); + + if (softirq_count() == (cnt & SOFTIRQ_MASK)) + lockdep_softirqs_on(_RET_IP_); + + __preempt_count_sub(cnt); +} + +/* + * Special-case - softirqs can safely be enabled by __do_softirq(), + * without processing still-pending softirqs: + */ +void _local_bh_enable(void) +{ + WARN_ON_ONCE(in_hardirq()); + __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_hardirq()); + lockdep_assert_irqs_enabled(); +#ifdef CONFIG_TRACE_IRQFLAGS + local_irq_disable(); +#endif + /* + * Are softirqs going to be turned on now: + */ + if (softirq_count() == SOFTIRQ_DISABLE_OFFSET) + lockdep_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); + +static inline void softirq_handle_begin(void) +{ + __local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET); +} + +static inline void softirq_handle_end(void) +{ + __local_bh_enable(SOFTIRQ_OFFSET); + WARN_ON_ONCE(in_interrupt()); +} + +static inline void ksoftirqd_run_begin(void) +{ + local_irq_disable(); +} + +static inline void ksoftirqd_run_end(void) +{ + local_irq_enable(); +} + +static inline bool should_wake_ksoftirqd(void) +{ + return true; +} + +static inline void invoke_softirq(void) +{ + if (!force_irqthreads() || !__this_cpu_read(ksoftirqd)) { +#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(); + } +} + +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); +} + +#endif /* !CONFIG_PREEMPT_RT */ + +/* + * 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 (lockdep_hardirq_context()) { + in_hardirq = true; + lockdep_hardirq_exit(); + } + + lockdep_softirq_enter(); + + return in_hardirq; +} + +static inline void lockdep_softirq_end(bool in_hardirq) +{ + lockdep_softirq_exit(); + + if (in_hardirq) + lockdep_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 __softirq_entry __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 as the 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 swapping. + */ + current->flags &= ~PF_MEMALLOC; + + pending = local_softirq_pending(); + + softirq_handle_begin(); + in_hardirq = lockdep_softirq_start(); + account_softirq_enter(current); + +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; + } + + if (!IS_ENABLED(CONFIG_PREEMPT_RT) && + __this_cpu_read(ksoftirqd) == current) + rcu_softirq_qs(); + + local_irq_disable(); + + pending = local_softirq_pending(); + if (pending) { + if (time_before(jiffies, end) && !need_resched() && + --max_restart) + goto restart; + + wakeup_softirqd(); + } + + account_softirq_exit(current); + lockdep_softirq_end(in_hardirq); + softirq_handle_end(); + current_restore_flags(old_flags, PF_MEMALLOC); +} + +/** + * irq_enter_rcu - Enter an interrupt context with RCU watching + */ +void irq_enter_rcu(void) +{ + __irq_enter_raw(); + + if (tick_nohz_full_cpu(smp_processor_id()) || + (is_idle_task(current) && (irq_count() == HARDIRQ_OFFSET))) + tick_irq_enter(); + + account_hardirq_enter(current); +} + +/** + * irq_enter - Enter an interrupt context including RCU update + */ +void irq_enter(void) +{ + ct_irq_enter(); + irq_enter_rcu(); +} + +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 ((sched_core_idle_cpu(cpu) && !need_resched()) || tick_nohz_full_cpu(cpu)) { + if (!in_hardirq()) + tick_nohz_irq_exit(); + } +#endif +} + +static inline void __irq_exit_rcu(void) +{ +#ifndef __ARCH_IRQ_EXIT_IRQS_DISABLED + local_irq_disable(); +#else + lockdep_assert_irqs_disabled(); +#endif + account_hardirq_exit(current); + preempt_count_sub(HARDIRQ_OFFSET); + if (!in_interrupt() && local_softirq_pending()) + invoke_softirq(); + + tick_irq_exit(); +} + +/** + * irq_exit_rcu() - Exit an interrupt context without updating RCU + * + * Also processes softirqs if needed and possible. + */ +void irq_exit_rcu(void) +{ + __irq_exit_rcu(); + /* must be last! */ + lockdep_hardirq_exit(); +} + +/** + * irq_exit - Exit an interrupt context, update RCU and lockdep + * + * Also processes softirqs if needed and possible. + */ +void irq_exit(void) +{ + __irq_exit_rcu(); + ct_irq_exit(); + /* must be last! */ + lockdep_hardirq_exit(); +} + +/* + * 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() && should_wake_ksoftirqd()) + 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) +{ + lockdep_assert_irqs_disabled(); + 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); + +static void __tasklet_schedule_common(struct tasklet_struct *t, + struct tasklet_head __percpu *headp, + unsigned int softirq_nr) +{ + struct tasklet_head *head; + unsigned long flags; + + local_irq_save(flags); + head = this_cpu_ptr(headp); + t->next = NULL; + *head->tail = t; + head->tail = &(t->next); + raise_softirq_irqoff(softirq_nr); + local_irq_restore(flags); +} + +void __tasklet_schedule(struct tasklet_struct *t) +{ + __tasklet_schedule_common(t, &tasklet_vec, + TASKLET_SOFTIRQ); +} +EXPORT_SYMBOL(__tasklet_schedule); + +void __tasklet_hi_schedule(struct tasklet_struct *t) +{ + __tasklet_schedule_common(t, &tasklet_hi_vec, + HI_SOFTIRQ); +} +EXPORT_SYMBOL(__tasklet_hi_schedule); + +static bool tasklet_clear_sched(struct tasklet_struct *t) +{ + if (test_and_clear_bit(TASKLET_STATE_SCHED, &t->state)) { + wake_up_var(&t->state); + return true; + } + + WARN_ONCE(1, "tasklet SCHED state not set: %s %pS\n", + t->use_callback ? "callback" : "func", + t->use_callback ? (void *)t->callback : (void *)t->func); + + return false; +} + +static void tasklet_action_common(struct softirq_action *a, + struct tasklet_head *tl_head, + unsigned int softirq_nr) +{ + struct tasklet_struct *list; + + local_irq_disable(); + list = tl_head->head; + tl_head->head = NULL; + tl_head->tail = &tl_head->head; + local_irq_enable(); + + while (list) { + struct tasklet_struct *t = list; + + list = list->next; + + if (tasklet_trylock(t)) { + if (!atomic_read(&t->count)) { + if (tasklet_clear_sched(t)) { + if (t->use_callback) { + trace_tasklet_entry(t, t->callback); + t->callback(t); + trace_tasklet_exit(t, t->callback); + } else { + trace_tasklet_entry(t, t->func); + t->func(t->data); + trace_tasklet_exit(t, t->func); + } + } + tasklet_unlock(t); + continue; + } + tasklet_unlock(t); + } + + local_irq_disable(); + t->next = NULL; + *tl_head->tail = t; + tl_head->tail = &t->next; + __raise_softirq_irqoff(softirq_nr); + local_irq_enable(); + } +} + +static __latent_entropy void tasklet_action(struct softirq_action *a) +{ + tasklet_action_common(a, this_cpu_ptr(&tasklet_vec), TASKLET_SOFTIRQ); +} + +static __latent_entropy void tasklet_hi_action(struct softirq_action *a) +{ + tasklet_action_common(a, this_cpu_ptr(&tasklet_hi_vec), HI_SOFTIRQ); +} + +void tasklet_setup(struct tasklet_struct *t, + void (*callback)(struct tasklet_struct *)) +{ + t->next = NULL; + t->state = 0; + atomic_set(&t->count, 0); + t->callback = callback; + t->use_callback = true; + t->data = 0; +} +EXPORT_SYMBOL(tasklet_setup); + +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->use_callback = false; + t->data = data; +} +EXPORT_SYMBOL(tasklet_init); + +#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT) +/* + * Do not use in new code. Waiting for tasklets from atomic contexts is + * error prone and should be avoided. + */ +void tasklet_unlock_spin_wait(struct tasklet_struct *t) +{ + while (test_bit(TASKLET_STATE_RUN, &(t)->state)) { + if (IS_ENABLED(CONFIG_PREEMPT_RT)) { + /* + * Prevent a live lock when current preempted soft + * interrupt processing or prevents ksoftirqd from + * running. If the tasklet runs on a different CPU + * then this has no effect other than doing the BH + * disable/enable dance for nothing. + */ + local_bh_disable(); + local_bh_enable(); + } else { + cpu_relax(); + } + } +} +EXPORT_SYMBOL(tasklet_unlock_spin_wait); +#endif + +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)) + wait_var_event(&t->state, !test_bit(TASKLET_STATE_SCHED, &t->state)); + + tasklet_unlock_wait(t); + tasklet_clear_sched(t); +} +EXPORT_SYMBOL(tasklet_kill); + +#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT) +void tasklet_unlock(struct tasklet_struct *t) +{ + smp_mb__before_atomic(); + clear_bit(TASKLET_STATE_RUN, &t->state); + smp_mb__after_atomic(); + wake_up_var(&t->state); +} +EXPORT_SYMBOL_GPL(tasklet_unlock); + +void tasklet_unlock_wait(struct tasklet_struct *t) +{ + wait_var_event(&t->state, !test_bit(TASKLET_STATE_RUN, &t->state)); +} +EXPORT_SYMBOL_GPL(tasklet_unlock_wait); +#endif + +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) +{ + ksoftirqd_run_begin(); + if (local_softirq_pending()) { + /* + * We can safely run softirq on inline stack, as we are not deep + * in the task stack here. + */ + __do_softirq(); + ksoftirqd_run_end(); + cond_resched(); + return; + } + ksoftirqd_run_end(); +} + +#ifdef CONFIG_HOTPLUG_CPU +static int 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(); + return 0; +} +#else +#define takeover_tasklets NULL +#endif /* CONFIG_HOTPLUG_CPU */ + +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) +{ + cpuhp_setup_state_nocalls(CPUHP_SOFTIRQ_DEAD, "softirq:dead", NULL, + takeover_tasklets); + 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; +} |