* Steven Rostedt | 2016-05-26 19:56:41 [-0400]:
>For example:
>
> <interrupt thread (as all interrupts on RT are threaded>
>
> napi_schedule_prep()
> test_and_set_bit(NAPI_STATE_SCHED, &n->state)
>
> <preempted by higher prio task that runs softirqs in its context>
>
> sk_busy_loop()
>
> do {
> rc = busy_poll()
> ret = napi_schedule_prep()
> return !test_and_set_bit(NAPI_STATE_SCHED, &n->state)
> <returns zero because NAPI_STATE_SCHED is set>
> if (!ret) return 0
> <rc is zero>
> } while (...) /* for ever */
>
No, I don't see the busyloop. while() is here:
| while (!nonblock && skb_queue_empty(&sk->sk_receive_queue) &&
| !need_resched() && !busy_loop_timeout(end_time));
and this seems to be the case since v3.11 where it was introduced (but
now it moved to dev.c). So even if there is no busy_poll() and
napi_schedule_prep() returns 0 our cycles here are limited by
busy_loop_timeout().
Sebastian
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