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690 lines
16 KiB
690 lines
16 KiB
/*
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* linux/kernel/softirq.c
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*
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* Copyright (C) 1992 Linus Torvalds
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*
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* Distribute under GPLv2.
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*
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* Rewritten. Old one was good in 2.2, but in 2.3 it was immoral. --ANK (990903)
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*/
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#include <linux/module.h>
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#include <linux/kernel_stat.h>
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#include <linux/interrupt.h>
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#include <linux/init.h>
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#include <linux/mm.h>
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#include <linux/notifier.h>
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#include <linux/percpu.h>
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#include <linux/cpu.h>
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#include <linux/freezer.h>
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#include <linux/kthread.h>
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#include <linux/rcupdate.h>
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#include <linux/smp.h>
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#include <linux/tick.h>
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#include <asm/irq.h>
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/*
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- No shared variables, all the data are CPU local.
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- If a softirq needs serialization, let it serialize itself
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by its own spinlocks.
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- Even if softirq is serialized, only local cpu is marked for
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execution. Hence, we get something sort of weak cpu binding.
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Though it is still not clear, will it result in better locality
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or will not.
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Examples:
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- NET RX softirq. It is multithreaded and does not require
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any global serialization.
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- NET TX softirq. It kicks software netdevice queues, hence
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it is logically serialized per device, but this serialization
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is invisible to common code.
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- Tasklets: serialized wrt itself.
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*/
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#ifndef __ARCH_IRQ_STAT
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irq_cpustat_t irq_stat[NR_CPUS] ____cacheline_aligned;
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EXPORT_SYMBOL(irq_stat);
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#endif
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static struct softirq_action softirq_vec[32] __cacheline_aligned_in_smp;
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static DEFINE_PER_CPU(struct task_struct *, ksoftirqd);
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/*
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* we cannot loop indefinitely here to avoid userspace starvation,
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* but we also don't want to introduce a worst case 1/HZ latency
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* to the pending events, so lets the scheduler to balance
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* the softirq load for us.
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*/
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static inline void wakeup_softirqd(void)
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{
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/* Interrupts are disabled: no need to stop preemption */
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struct task_struct *tsk = __get_cpu_var(ksoftirqd);
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if (tsk && tsk->state != TASK_RUNNING)
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wake_up_process(tsk);
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}
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/*
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* This one is for softirq.c-internal use,
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* where hardirqs are disabled legitimately:
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*/
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#ifdef CONFIG_TRACE_IRQFLAGS
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static void __local_bh_disable(unsigned long ip)
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{
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unsigned long flags;
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WARN_ON_ONCE(in_irq());
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raw_local_irq_save(flags);
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add_preempt_count(SOFTIRQ_OFFSET);
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/*
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* Were softirqs turned off above:
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*/
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if (softirq_count() == SOFTIRQ_OFFSET)
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trace_softirqs_off(ip);
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raw_local_irq_restore(flags);
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}
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#else /* !CONFIG_TRACE_IRQFLAGS */
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static inline void __local_bh_disable(unsigned long ip)
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{
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add_preempt_count(SOFTIRQ_OFFSET);
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barrier();
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}
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#endif /* CONFIG_TRACE_IRQFLAGS */
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void local_bh_disable(void)
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{
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__local_bh_disable((unsigned long)__builtin_return_address(0));
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}
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EXPORT_SYMBOL(local_bh_disable);
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void __local_bh_enable(void)
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{
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WARN_ON_ONCE(in_irq());
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/*
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* softirqs should never be enabled by __local_bh_enable(),
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* it always nests inside local_bh_enable() sections:
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*/
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WARN_ON_ONCE(softirq_count() == SOFTIRQ_OFFSET);
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sub_preempt_count(SOFTIRQ_OFFSET);
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}
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EXPORT_SYMBOL_GPL(__local_bh_enable);
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/*
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* Special-case - softirqs can safely be enabled in
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* cond_resched_softirq(), or by __do_softirq(),
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* without processing still-pending softirqs:
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*/
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void _local_bh_enable(void)
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{
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WARN_ON_ONCE(in_irq());
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WARN_ON_ONCE(!irqs_disabled());
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if (softirq_count() == SOFTIRQ_OFFSET)
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trace_softirqs_on((unsigned long)__builtin_return_address(0));
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sub_preempt_count(SOFTIRQ_OFFSET);
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}
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EXPORT_SYMBOL(_local_bh_enable);
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void local_bh_enable(void)
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{
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#ifdef CONFIG_TRACE_IRQFLAGS
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unsigned long flags;
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WARN_ON_ONCE(in_irq());
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#endif
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WARN_ON_ONCE(irqs_disabled());
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#ifdef CONFIG_TRACE_IRQFLAGS
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local_irq_save(flags);
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#endif
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/*
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* Are softirqs going to be turned on now:
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*/
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if (softirq_count() == SOFTIRQ_OFFSET)
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trace_softirqs_on((unsigned long)__builtin_return_address(0));
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/*
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* Keep preemption disabled until we are done with
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* softirq processing:
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*/
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sub_preempt_count(SOFTIRQ_OFFSET - 1);
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if (unlikely(!in_interrupt() && local_softirq_pending()))
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do_softirq();
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dec_preempt_count();
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#ifdef CONFIG_TRACE_IRQFLAGS
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local_irq_restore(flags);
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#endif
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preempt_check_resched();
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}
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EXPORT_SYMBOL(local_bh_enable);
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void local_bh_enable_ip(unsigned long ip)
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{
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#ifdef CONFIG_TRACE_IRQFLAGS
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unsigned long flags;
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WARN_ON_ONCE(in_irq());
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local_irq_save(flags);
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#endif
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/*
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* Are softirqs going to be turned on now:
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*/
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if (softirq_count() == SOFTIRQ_OFFSET)
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trace_softirqs_on(ip);
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/*
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* Keep preemption disabled until we are done with
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* softirq processing:
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*/
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sub_preempt_count(SOFTIRQ_OFFSET - 1);
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if (unlikely(!in_interrupt() && local_softirq_pending()))
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do_softirq();
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dec_preempt_count();
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#ifdef CONFIG_TRACE_IRQFLAGS
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local_irq_restore(flags);
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#endif
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preempt_check_resched();
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}
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EXPORT_SYMBOL(local_bh_enable_ip);
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/*
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* We restart softirq processing MAX_SOFTIRQ_RESTART times,
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* and we fall back to softirqd after that.
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*
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* This number has been established via experimentation.
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* The two things to balance is latency against fairness -
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* we want to handle softirqs as soon as possible, but they
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* should not be able to lock up the box.
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*/
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#define MAX_SOFTIRQ_RESTART 10
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asmlinkage void __do_softirq(void)
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{
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struct softirq_action *h;
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__u32 pending;
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int max_restart = MAX_SOFTIRQ_RESTART;
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int cpu;
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pending = local_softirq_pending();
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account_system_vtime(current);
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__local_bh_disable((unsigned long)__builtin_return_address(0));
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trace_softirq_enter();
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cpu = smp_processor_id();
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restart:
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/* Reset the pending bitmask before enabling irqs */
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set_softirq_pending(0);
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local_irq_enable();
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h = softirq_vec;
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do {
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if (pending & 1) {
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h->action(h);
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rcu_bh_qsctr_inc(cpu);
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}
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h++;
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pending >>= 1;
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} while (pending);
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local_irq_disable();
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pending = local_softirq_pending();
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if (pending && --max_restart)
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goto restart;
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if (pending)
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wakeup_softirqd();
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trace_softirq_exit();
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account_system_vtime(current);
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_local_bh_enable();
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}
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#ifndef __ARCH_HAS_DO_SOFTIRQ
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asmlinkage void do_softirq(void)
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{
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__u32 pending;
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unsigned long flags;
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if (in_interrupt())
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return;
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local_irq_save(flags);
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pending = local_softirq_pending();
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if (pending)
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__do_softirq();
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local_irq_restore(flags);
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}
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#endif
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/*
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* Enter an interrupt context.
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*/
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void irq_enter(void)
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{
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#ifdef CONFIG_NO_HZ
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int cpu = smp_processor_id();
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if (idle_cpu(cpu) && !in_interrupt())
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tick_nohz_stop_idle(cpu);
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#endif
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__irq_enter();
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#ifdef CONFIG_NO_HZ
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if (idle_cpu(cpu))
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tick_nohz_update_jiffies();
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#endif
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}
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#ifdef __ARCH_IRQ_EXIT_IRQS_DISABLED
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# define invoke_softirq() __do_softirq()
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#else
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# define invoke_softirq() do_softirq()
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#endif
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/*
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* Exit an interrupt context. Process softirqs if needed and possible:
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*/
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void irq_exit(void)
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{
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account_system_vtime(current);
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trace_hardirq_exit();
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sub_preempt_count(IRQ_EXIT_OFFSET);
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if (!in_interrupt() && local_softirq_pending())
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invoke_softirq();
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#ifdef CONFIG_NO_HZ
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/* Make sure that timer wheel updates are propagated */
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if (!in_interrupt() && idle_cpu(smp_processor_id()) && !need_resched())
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tick_nohz_stop_sched_tick();
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rcu_irq_exit();
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#endif
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preempt_enable_no_resched();
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}
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/*
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* This function must run with irqs disabled!
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*/
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inline void raise_softirq_irqoff(unsigned int nr)
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{
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__raise_softirq_irqoff(nr);
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/*
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* If we're in an interrupt or softirq, we're done
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* (this also catches softirq-disabled code). We will
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* actually run the softirq once we return from
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* the irq or softirq.
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*
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* Otherwise we wake up ksoftirqd to make sure we
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* schedule the softirq soon.
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*/
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if (!in_interrupt())
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wakeup_softirqd();
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}
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void raise_softirq(unsigned int nr)
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{
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unsigned long flags;
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local_irq_save(flags);
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raise_softirq_irqoff(nr);
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local_irq_restore(flags);
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}
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void open_softirq(int nr, void (*action)(struct softirq_action*), void *data)
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{
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softirq_vec[nr].data = data;
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softirq_vec[nr].action = action;
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}
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/* Tasklets */
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struct tasklet_head
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{
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struct tasklet_struct *head;
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struct tasklet_struct **tail;
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};
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/* Some compilers disobey section attribute on statics when not
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initialized -- RR */
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static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec) = { NULL };
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static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec) = { NULL };
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void __tasklet_schedule(struct tasklet_struct *t)
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{
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unsigned long flags;
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local_irq_save(flags);
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t->next = NULL;
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*__get_cpu_var(tasklet_vec).tail = t;
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__get_cpu_var(tasklet_vec).tail = &(t->next);
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raise_softirq_irqoff(TASKLET_SOFTIRQ);
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local_irq_restore(flags);
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}
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EXPORT_SYMBOL(__tasklet_schedule);
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void __tasklet_hi_schedule(struct tasklet_struct *t)
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{
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unsigned long flags;
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local_irq_save(flags);
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t->next = NULL;
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*__get_cpu_var(tasklet_hi_vec).tail = t;
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__get_cpu_var(tasklet_hi_vec).tail = &(t->next);
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raise_softirq_irqoff(HI_SOFTIRQ);
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local_irq_restore(flags);
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}
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EXPORT_SYMBOL(__tasklet_hi_schedule);
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static void tasklet_action(struct softirq_action *a)
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{
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struct tasklet_struct *list;
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local_irq_disable();
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list = __get_cpu_var(tasklet_vec).head;
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__get_cpu_var(tasklet_vec).head = NULL;
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__get_cpu_var(tasklet_vec).tail = &__get_cpu_var(tasklet_vec).head;
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local_irq_enable();
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while (list) {
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struct tasklet_struct *t = list;
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list = list->next;
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if (tasklet_trylock(t)) {
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if (!atomic_read(&t->count)) {
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if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state))
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BUG();
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t->func(t->data);
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tasklet_unlock(t);
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continue;
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}
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tasklet_unlock(t);
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}
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local_irq_disable();
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t->next = NULL;
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*__get_cpu_var(tasklet_vec).tail = t;
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__get_cpu_var(tasklet_vec).tail = &(t->next);
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__raise_softirq_irqoff(TASKLET_SOFTIRQ);
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local_irq_enable();
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}
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}
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static void tasklet_hi_action(struct softirq_action *a)
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{
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struct tasklet_struct *list;
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local_irq_disable();
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list = __get_cpu_var(tasklet_hi_vec).head;
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__get_cpu_var(tasklet_hi_vec).head = NULL;
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__get_cpu_var(tasklet_hi_vec).tail = &__get_cpu_var(tasklet_hi_vec).head;
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local_irq_enable();
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while (list) {
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struct tasklet_struct *t = list;
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list = list->next;
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if (tasklet_trylock(t)) {
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if (!atomic_read(&t->count)) {
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if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state))
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BUG();
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t->func(t->data);
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tasklet_unlock(t);
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continue;
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}
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tasklet_unlock(t);
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}
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local_irq_disable();
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t->next = NULL;
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*__get_cpu_var(tasklet_hi_vec).tail = t;
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__get_cpu_var(tasklet_hi_vec).tail = &(t->next);
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__raise_softirq_irqoff(HI_SOFTIRQ);
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local_irq_enable();
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}
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}
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void tasklet_init(struct tasklet_struct *t,
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void (*func)(unsigned long), unsigned long data)
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{
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t->next = NULL;
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t->state = 0;
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atomic_set(&t->count, 0);
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t->func = func;
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t->data = data;
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}
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EXPORT_SYMBOL(tasklet_init);
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void tasklet_kill(struct tasklet_struct *t)
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{
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if (in_interrupt())
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printk("Attempt to kill tasklet from interrupt\n");
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while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) {
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do
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yield();
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while (test_bit(TASKLET_STATE_SCHED, &t->state));
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}
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tasklet_unlock_wait(t);
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clear_bit(TASKLET_STATE_SCHED, &t->state);
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}
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EXPORT_SYMBOL(tasklet_kill);
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void __init softirq_init(void)
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{
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int cpu;
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for_each_possible_cpu(cpu) {
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per_cpu(tasklet_vec, cpu).tail =
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&per_cpu(tasklet_vec, cpu).head;
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per_cpu(tasklet_hi_vec, cpu).tail =
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&per_cpu(tasklet_hi_vec, cpu).head;
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}
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open_softirq(TASKLET_SOFTIRQ, tasklet_action, NULL);
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open_softirq(HI_SOFTIRQ, tasklet_hi_action, NULL);
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}
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static int ksoftirqd(void * __bind_cpu)
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{
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set_current_state(TASK_INTERRUPTIBLE);
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while (!kthread_should_stop()) {
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preempt_disable();
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if (!local_softirq_pending()) {
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preempt_enable_no_resched();
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schedule();
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preempt_disable();
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}
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__set_current_state(TASK_RUNNING);
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while (local_softirq_pending()) {
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/* Preempt disable stops cpu going offline.
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If already offline, we'll be on wrong CPU:
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don't process */
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if (cpu_is_offline((long)__bind_cpu))
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goto wait_to_die;
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do_softirq();
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preempt_enable_no_resched();
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cond_resched();
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preempt_disable();
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}
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preempt_enable();
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set_current_state(TASK_INTERRUPTIBLE);
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}
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__set_current_state(TASK_RUNNING);
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return 0;
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wait_to_die:
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preempt_enable();
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/* Wait for kthread_stop */
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set_current_state(TASK_INTERRUPTIBLE);
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while (!kthread_should_stop()) {
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schedule();
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set_current_state(TASK_INTERRUPTIBLE);
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}
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__set_current_state(TASK_RUNNING);
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return 0;
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}
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#ifdef CONFIG_HOTPLUG_CPU
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/*
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* tasklet_kill_immediate is called to remove a tasklet which can already be
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* scheduled for execution on @cpu.
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*
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* Unlike tasklet_kill, this function removes the tasklet
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* _immediately_, even if the tasklet is in TASKLET_STATE_SCHED state.
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*
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|
* 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) {
|
|
*(__get_cpu_var(tasklet_vec).tail) = per_cpu(tasklet_vec, cpu).head;
|
|
__get_cpu_var(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) {
|
|
*__get_cpu_var(tasklet_hi_vec).tail = per_cpu(tasklet_hi_vec, cpu).head;
|
|
__get_cpu_var(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 __cpuinit cpu_callback(struct notifier_block *nfb,
|
|
unsigned long action,
|
|
void *hcpu)
|
|
{
|
|
int hotcpu = (unsigned long)hcpu;
|
|
struct task_struct *p;
|
|
|
|
switch (action) {
|
|
case CPU_UP_PREPARE:
|
|
case CPU_UP_PREPARE_FROZEN:
|
|
p = kthread_create(ksoftirqd, hcpu, "ksoftirqd/%d", hotcpu);
|
|
if (IS_ERR(p)) {
|
|
printk("ksoftirqd for %i failed\n", hotcpu);
|
|
return NOTIFY_BAD;
|
|
}
|
|
kthread_bind(p, hotcpu);
|
|
per_cpu(ksoftirqd, hotcpu) = p;
|
|
break;
|
|
case CPU_ONLINE:
|
|
case CPU_ONLINE_FROZEN:
|
|
wake_up_process(per_cpu(ksoftirqd, hotcpu));
|
|
break;
|
|
#ifdef CONFIG_HOTPLUG_CPU
|
|
case CPU_UP_CANCELED:
|
|
case CPU_UP_CANCELED_FROZEN:
|
|
if (!per_cpu(ksoftirqd, hotcpu))
|
|
break;
|
|
/* Unbind so it can run. Fall thru. */
|
|
kthread_bind(per_cpu(ksoftirqd, hotcpu),
|
|
any_online_cpu(cpu_online_map));
|
|
case CPU_DEAD:
|
|
case CPU_DEAD_FROZEN: {
|
|
struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
|
|
|
|
p = per_cpu(ksoftirqd, hotcpu);
|
|
per_cpu(ksoftirqd, hotcpu) = NULL;
|
|
sched_setscheduler(p, SCHED_FIFO, ¶m);
|
|
kthread_stop(p);
|
|
takeover_tasklets(hotcpu);
|
|
break;
|
|
}
|
|
#endif /* CONFIG_HOTPLUG_CPU */
|
|
}
|
|
return NOTIFY_OK;
|
|
}
|
|
|
|
static struct notifier_block __cpuinitdata cpu_nfb = {
|
|
.notifier_call = cpu_callback
|
|
};
|
|
|
|
__init int spawn_ksoftirqd(void)
|
|
{
|
|
void *cpu = (void *)(long)smp_processor_id();
|
|
int err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
|
|
|
|
BUG_ON(err == NOTIFY_BAD);
|
|
cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
|
|
register_cpu_notifier(&cpu_nfb);
|
|
return 0;
|
|
}
|
|
|
|
#ifdef CONFIG_SMP
|
|
/*
|
|
* Call a function on all processors
|
|
*/
|
|
int on_each_cpu(void (*func) (void *info), void *info, int retry, int wait)
|
|
{
|
|
int ret = 0;
|
|
|
|
preempt_disable();
|
|
ret = smp_call_function(func, info, retry, wait);
|
|
local_irq_disable();
|
|
func(info);
|
|
local_irq_enable();
|
|
preempt_enable();
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(on_each_cpu);
|
|
#endif
|
|
|