| // 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> |
| |
| EXPORT_TRACEPOINT_SYMBOL_GPL(irq_handler_entry); |
| |
| /* |
| - 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); |
| EXPORT_PER_CPU_SYMBOL_GPL(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); |
| } |
| |
| /* |
| * If ksoftirqd is scheduled, we do not want to process pending softirqs |
| * right now. Let ksoftirqd handle this at its own rate, to get fairness, |
| * unless we're doing some of the synchronous softirqs. |
| */ |
| #define SOFTIRQ_NOW_MASK ((1 << HI_SOFTIRQ) | (1 << TASKLET_SOFTIRQ)) |
| static bool ksoftirqd_running(unsigned long pending) |
| { |
| struct task_struct *tsk = __this_cpu_read(ksoftirqd); |
| |
| if (pending & SOFTIRQ_NOW_MASK) |
| return false; |
| return tsk && task_is_running(tsk) && !__kthread_should_park(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 || ksoftirqd_running(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 (ksoftirqd_running(local_softirq_pending())) |
| return; |
| |
| 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 && !ksoftirqd_running(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 ((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; |
| } |