sirq/hoghogeってなに?

2012/07/05 Linux::task

"sirq-XXX"とは?

コレ参考になる。筑波大学の講義か。
http://www.coins.tsukuba.ac.jp/~yas/coins/os2-2011/2012-02-14/

要約すると??

優先度の高いtaskで、driverのbottom halfやprotocol stackの処理を行う。
kernel threadで、SMPならcoreごとに名前が異なる。("ksoftirqd/0","ksoftirqd/1"とか)

ソースコードを追う

FILE: kernel/softirq.c

static const char *softirq_names [] =
{
  [HI_SOFTIRQ]		= "high",
  [SCHED_SOFTIRQ]	= "sched",
  [TIMER_SOFTIRQ]	= "timer",
  [NET_TX_SOFTIRQ]	= "net-tx",
  [NET_RX_SOFTIRQ]	= "net-rx",
  [BLOCK_SOFTIRQ]	= "block",
  [BLOCK_IOPOLL_SOFTIRQ]= "block-iopoll",
  [TASKLET_SOFTIRQ]	= "tasklet",
  [HRTIMER_SOFTIRQ]	= "hrtimer",
  [RCU_SOFTIRQ]		= "rcu",
};


static struct notifier_block __cpuinitdata cpu_nfb = {
	.notifier_call = cpu_callback
};

static __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;
}
early_initcall(spawn_ksoftirqd);
展開すると以下イメージで処理される。
cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
		for (i = 0; i < NR_SOFTIRQS; i++) {
			per_cpu(ksoftirqd, hotcpu)[i].nr = i;
			per_cpu(ksoftirqd, hotcpu)[i].cpu = hotcpu;
			per_cpu(ksoftirqd, hotcpu)[i].tsk = NULL;
		}
		for (i = 0; i < NR_SOFTIRQS; i++) {
			p = kthread_create(run_ksoftirqd,
					   &per_cpu(ksoftirqd, hotcpu)[i],
					   "sirq-%s/%d", softirq_names[i],
					   hotcpu);
			if (IS_ERR(p)) {
				printk("ksoftirqd %d for %i failed\n", i,
				       hotcpu);
				return NOTIFY_BAD;
			}
			kthread_bind(p, hotcpu);
			per_cpu(ksoftirqd, hotcpu)[i].tsk = p;
		}
cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
		for (i = 0; i < NR_SOFTIRQS; i++) {
			param.sched_priority = MAX_RT_PRIO-1;
			p = per_cpu(ksoftirqd, hotcpu)[i].tsk;
			sched_setscheduler(p, SCHED_FIFO, &param);
			per_cpu(ksoftirqd, hotcpu)[i].tsk = NULL;
			kthread_stop(p);
		}
		takeover_tasklets(hotcpu);
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