idle threads

[Attilio Rao]

2010/4/24 Matthew Fleming <matthew.fleming at isilon.com>:
> I'm looking at kern_idle.c in stable/7 and I don't quite follow how idle
> threads work.  The kthread_create(9) call does not pass in a function
> pointer, so what code does a processor run when there is no other
> runnable thread?

In STABLE_7:

...
#ifdef SMP
        SLIST_FOREACH(pc, &cpuhead, pc_allcpu) {
                error = kthread_create(sched_idletd, NULL, &p,
                    RFSTOPPED | RFHIGHPID, 0, "idle: cpu%d", pc->pc_cpuid);
                pc->pc_idlethread = FIRST_THREAD_IN_PROC(p);
#else
                error = kthread_create(sched_idletd, NULL, &p,
                    RFSTOPPED | RFHIGHPID, 0, "idle");
                PCPU_SET(idlethread, FIRST_THREAD_IN_PROC(p));
#endif
...

then they rightly passes sched_idletd(). Any scheduler may define its
own version of sched_idletd().
NULL is just the argument passed that is not meaningful.
Or maybe I'm not understanding your question?

Attilio


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