1 files changed, 496 insertions, 0 deletions
diff --git a/kernel/softirq.c b/kernel/softirq.c
new file mode 100644
index 000000000000..b4ab6af1dea8
--- /dev/null
+++ b/kernel/softirq.c
@@ -0,0 +1,496 @@
+/*
+ *	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)
+ */
+
+#include <linux/module.h>
+#include <linux/kernel_stat.h>
+#include <linux/interrupt.h>
+#include <linux/init.h>
+#include <linux/mm.h>
+#include <linux/notifier.h>
+#include <linux/percpu.h>
+#include <linux/cpu.h>
+#include <linux/kthread.h>
+#include <linux/rcupdate.h>
+
+#include <asm/irq.h>
+/*
+   - No shared variables, all the data are CPU local.
+   - If a softirq needs serialization, let it serialize itself
+     by its own spinlocks.
+   - Even if softirq is serialized, only local cpu is marked for
+     execution. Hence, we get something sort of weak cpu binding.
+     Though it is still not clear, will it result in better locality
+     or will not.
+
+   Examples:
+   - NET RX softirq. It is multithreaded and does not require
+     any global serialization.
+   - NET TX softirq. It kicks software netdevice queues, hence
+     it is logically serialized per device, but this serialization
+     is invisible to common code.
+   - Tasklets: serialized wrt itself.
+ */
+
+#ifndef __ARCH_IRQ_STAT
+irq_cpustat_t irq_stat[NR_CPUS] ____cacheline_aligned;
+EXPORT_SYMBOL(irq_stat);
+#endif
+
+static struct softirq_action softirq_vec[32] __cacheline_aligned_in_smp;
+
+static DEFINE_PER_CPU(struct task_struct *, ksoftirqd);
+
+/*
+ * 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 inline void wakeup_softirqd(void)
+{
+	/* Interrupts are disabled: no need to stop preemption */
+	struct task_struct *tsk = __get_cpu_var(ksoftirqd);
+
+	if (tsk && tsk->state != TASK_RUNNING)
+		wake_up_process(tsk);
+}
+
+/*
+ * We restart softirq processing MAX_SOFTIRQ_RESTART times,
+ * and we fall back to softirqd after that.
+ *
+ * This number has 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_RESTART 10
+
+asmlinkage void __do_softirq(void)
+{
+	struct softirq_action *h;
+	__u32 pending;
+	int max_restart = MAX_SOFTIRQ_RESTART;
+	int cpu;
+
+	pending = local_softirq_pending();
+
+	local_bh_disable();
+	cpu = smp_processor_id();
+restart:
+	/* Reset the pending bitmask before enabling irqs */
+	local_softirq_pending() = 0;
+
+	local_irq_enable();
+
+	h = softirq_vec;
+
+	do {
+		if (pending & 1) {
+			h->action(h);
+			rcu_bh_qsctr_inc(cpu);
+		}
+		h++;
+		pending >>= 1;
+	} while (pending);
+
+	local_irq_disable();
+
+	pending = local_softirq_pending();
+	if (pending && --max_restart)
+		goto restart;
+
+	if (pending)
+		wakeup_softirqd();
+
+	__local_bh_enable();
+}
+
+#ifndef __ARCH_HAS_DO_SOFTIRQ
+
+asmlinkage 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();
+
+	local_irq_restore(flags);
+}
+
+EXPORT_SYMBOL(do_softirq);
+
+#endif
+
+void local_bh_enable(void)
+{
+	WARN_ON(irqs_disabled());
+	/*
+	 * Keep preemption disabled until we are done with
+	 * softirq processing:
+ 	 */
+ 	sub_preempt_count(SOFTIRQ_OFFSET - 1);
+
+	if (unlikely(!in_interrupt() && local_softirq_pending()))
+		do_softirq();
+
+	dec_preempt_count();
+	preempt_check_resched();
+}
+EXPORT_SYMBOL(local_bh_enable);
+
+#ifdef __ARCH_IRQ_EXIT_IRQS_DISABLED
+# define invoke_softirq()	__do_softirq()
+#else
+# define invoke_softirq()	do_softirq()
+#endif
+
+/*
+ * Exit an interrupt context. Process softirqs if needed and possible:
+ */
+void irq_exit(void)
+{
+	account_system_vtime(current);
+	sub_preempt_count(IRQ_EXIT_OFFSET);
+	if (!in_interrupt() && local_softirq_pending())
+		invoke_softirq();
+	preempt_enable_no_resched();
+}
+
+/*
+ * This function must run with irqs disabled!
+ */
+inline fastcall void raise_softirq_irqoff(unsigned int nr)
+{
+	__raise_softirq_irqoff(nr);
+
+	/*
+	 * If we're in an interrupt or softirq, we're done
+	 * (this also catches softirq-disabled code). We will
+	 * actually run the softirq once we return from
+	 * the irq or softirq.
+	 *
+	 * Otherwise we wake up ksoftirqd to make sure we
+	 * schedule the softirq soon.
+	 */
+	if (!in_interrupt())
+		wakeup_softirqd();
+}
+
+EXPORT_SYMBOL(raise_softirq_irqoff);
+
+void fastcall raise_softirq(unsigned int nr)
+{
+	unsigned long flags;
+
+	local_irq_save(flags);
+	raise_softirq_irqoff(nr);
+	local_irq_restore(flags);
+}
+
+void open_softirq(int nr, void (*action)(struct softirq_action*), void *data)
+{
+	softirq_vec[nr].data = data;
+	softirq_vec[nr].action = action;
+}
+
+EXPORT_SYMBOL(open_softirq);
+
+/* Tasklets */
+struct tasklet_head
+{
+	struct tasklet_struct *list;
+};
+
+/* Some compilers disobey section attribute on statics when not
+   initialized -- RR */
+static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec) = { NULL };
+static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec) = { NULL };
+
+void fastcall __tasklet_schedule(struct tasklet_struct *t)
+{
+	unsigned long flags;
+
+	local_irq_save(flags);
+	t->next = __get_cpu_var(tasklet_vec).list;
+	__get_cpu_var(tasklet_vec).list = t;
+	raise_softirq_irqoff(TASKLET_SOFTIRQ);
+	local_irq_restore(flags);
+}
+
+EXPORT_SYMBOL(__tasklet_schedule);
+
+void fastcall __tasklet_hi_schedule(struct tasklet_struct *t)
+{
+	unsigned long flags;
+
+	local_irq_save(flags);
+	t->next = __get_cpu_var(tasklet_hi_vec).list;
+	__get_cpu_var(tasklet_hi_vec).list = t;
+	raise_softirq_irqoff(HI_SOFTIRQ);
+	local_irq_restore(flags);
+}
+
+EXPORT_SYMBOL(__tasklet_hi_schedule);
+
+static void tasklet_action(struct softirq_action *a)
+{
+	struct tasklet_struct *list;
+
+	local_irq_disable();
+	list = __get_cpu_var(tasklet_vec).list;
+	__get_cpu_var(tasklet_vec).list = NULL;
+	local_irq_enable();
+
+	while (list) {
+		struct tasklet_struct *t = list;
+
+		list = list->next;
+
+		if (tasklet_trylock(t)) {
+			if (!atomic_read(&t->count)) {
+				if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state))
+					BUG();
+				t->func(t->data);
+				tasklet_unlock(t);
+				continue;
+			}
+			tasklet_unlock(t);
+		}
+
+		local_irq_disable();
+		t->next = __get_cpu_var(tasklet_vec).list;
+		__get_cpu_var(tasklet_vec).list = t;
+		__raise_softirq_irqoff(TASKLET_SOFTIRQ);
+		local_irq_enable();
+	}
+}
+
+static void tasklet_hi_action(struct softirq_action *a)
+{
+	struct tasklet_struct *list;
+
+	local_irq_disable();
+	list = __get_cpu_var(tasklet_hi_vec).list;
+	__get_cpu_var(tasklet_hi_vec).list = NULL;
+	local_irq_enable();
+
+	while (list) {
+		struct tasklet_struct *t = list;
+
+		list = list->next;
+
+		if (tasklet_trylock(t)) {
+			if (!atomic_read(&t->count)) {
+				if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state))
+					BUG();
+				t->func(t->data);
+				tasklet_unlock(t);
+				continue;
+			}
+			tasklet_unlock(t);
+		}
+
+		local_irq_disable();
+		t->next = __get_cpu_var(tasklet_hi_vec).list;
+		__get_cpu_var(tasklet_hi_vec).list = t;
+		__raise_softirq_irqoff(HI_SOFTIRQ);
+		local_irq_enable();
+	}
+}
+
+
+void tasklet_init(struct tasklet_struct *t,
+		  void (*func)(unsigned long), unsigned long data)
+{
+	t->next = NULL;
+	t->state = 0;
+	atomic_set(&t->count, 0);
+	t->func = func;
+	t->data = data;
+}
+
+EXPORT_SYMBOL(tasklet_init);
+
+void tasklet_kill(struct tasklet_struct *t)
+{
+	if (in_interrupt())
+		printk("Attempt to kill tasklet from interrupt\n");
+
+	while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) {
+		do
+			yield();
+		while (test_bit(TASKLET_STATE_SCHED, &t->state));
+	}
+	tasklet_unlock_wait(t);
+	clear_bit(TASKLET_STATE_SCHED, &t->state);
+}
+
+EXPORT_SYMBOL(tasklet_kill);
+
+void __init softirq_init(void)
+{
+	open_softirq(TASKLET_SOFTIRQ, tasklet_action, NULL);
+	open_softirq(HI_SOFTIRQ, tasklet_hi_action, NULL);
+}
+
+static int ksoftirqd(void * __bind_cpu)
+{
+	set_user_nice(current, 19);
+	current->flags |= PF_NOFREEZE;
+
+	set_current_state(TASK_INTERRUPTIBLE);
+
+	while (!kthread_should_stop()) {
+		preempt_disable();
+		if (!local_softirq_pending()) {
+			preempt_enable_no_resched();
+			schedule();
+			preempt_disable();
+		}
+
+		__set_current_state(TASK_RUNNING);
+
+		while (local_softirq_pending()) {
+			/* Preempt disable stops cpu going offline.
+			   If already offline, we'll be on wrong CPU:
+			   don't process */
+			if (cpu_is_offline((long)__bind_cpu))
+				goto wait_to_die;
+			do_softirq();
+			preempt_enable_no_resched();
+			cond_resched();
+			preempt_disable();
+		}
+		preempt_enable();
+		set_current_state(TASK_INTERRUPTIBLE);
+	}
+	__set_current_state(TASK_RUNNING);
+	return 0;
+
+wait_to_die:
+	preempt_enable();
+	/* Wait for kthread_stop */
+	set_current_state(TASK_INTERRUPTIBLE);
+	while (!kthread_should_stop()) {
+		schedule();
+		set_current_state(TASK_INTERRUPTIBLE);
+	}
+	__set_current_state(TASK_RUNNING);
+	return 0;
+}
+
+#ifdef CONFIG_HOTPLUG_CPU
+/*
+ * tasklet_kill_immediate is called to remove a tasklet which can already be
+ * scheduled for execution on @cpu.
+ *
+ * Unlike tasklet_kill, this function removes the tasklet
+ * _immediately_, even if the tasklet is in TASKLET_STATE_SCHED state.
+ *
+ * When this function is called, @cpu must be in the CPU_DEAD state.
+ */
+void tasklet_kill_immediate(struct tasklet_struct *t, unsigned int cpu)
+{
+	struct tasklet_struct **i;
+
+	BUG_ON(cpu_online(cpu));
+	BUG_ON(test_bit(TASKLET_STATE_RUN, &t->state));
+
+	if (!test_bit(TASKLET_STATE_SCHED, &t->state))
+		return;
+
+	/* CPU is dead, so no lock needed. */
+	for (i = &per_cpu(tasklet_vec, cpu).list; *i; i = &(*i)->next) {
+		if (*i == t) {
+			*i = t->next;
+			return;
+		}
+	}
+	BUG();
+}
+
+static void takeover_tasklets(unsigned int cpu)
+{
+	struct tasklet_struct **i;
+
+	/* CPU is dead, so no lock needed. */
+	local_irq_disable();
+
+	/* Find end, append list for that CPU. */
+	for (i = &__get_cpu_var(tasklet_vec).list; *i; i = &(*i)->next);
+	*i = per_cpu(tasklet_vec, cpu).list;
+	per_cpu(tasklet_vec, cpu).list = NULL;
+	raise_softirq_irqoff(TASKLET_SOFTIRQ);
+
+	for (i = &__get_cpu_var(tasklet_hi_vec).list; *i; i = &(*i)->next);
+	*i = per_cpu(tasklet_hi_vec, cpu).list;
+	per_cpu(tasklet_hi_vec, cpu).list = NULL;
+	raise_softirq_irqoff(HI_SOFTIRQ);
+
+	local_irq_enable();
+}
+#endif /* CONFIG_HOTPLUG_CPU */
+
+static int __devinit 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:
+		BUG_ON(per_cpu(tasklet_vec, hotcpu).list);
+		BUG_ON(per_cpu(tasklet_hi_vec, hotcpu).list);
+		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:
+		wake_up_process(per_cpu(ksoftirqd, hotcpu));
+		break;
+#ifdef CONFIG_HOTPLUG_CPU
+	case CPU_UP_CANCELED:
+		/* Unbind so it can run.  Fall thru. */
+		kthread_bind(per_cpu(ksoftirqd, hotcpu), smp_processor_id());
+	case CPU_DEAD:
+		p = per_cpu(ksoftirqd, hotcpu);
+		per_cpu(ksoftirqd, hotcpu) = NULL;
+		kthread_stop(p);
+		takeover_tasklets(hotcpu);
+		break;
+#endif /* CONFIG_HOTPLUG_CPU */
+ 	}
+	return NOTIFY_OK;
+}
+
+static struct notifier_block __devinitdata cpu_nfb = {
+	.notifier_call = cpu_callback
+};
+
+__init int spawn_ksoftirqd(void)
+{
+	void *cpu = (void *)(long)smp_processor_id();
+	cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
+	cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
+	register_cpu_notifier(&cpu_nfb);
+	return 0;
+}