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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /kernel/softirq.c
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
Diffstat (limited to 'kernel/softirq.c')
-rw-r--r--kernel/softirq.c496
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;
+}

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