Re: [RFC][PATCH v8 1/2] printk: Make printk() completely async

Sergey Senozhatsky
2016-04-04T16:03:20Z

Hello,

On (04/04/16 11:41), Petr Mladek wrote:
[..]
> > So what about having printk_kthread_func() like:
> >
> > while (1) {
> > set_current_state(TASK_INTERRUPTIBLE);
> > if (!need_flush_console)
> > schedule();
> > __set_current_state(TASK_RUNNING);
> > need_flush_console = false;
> > console_lock();
> > console_unlock();
> > }
> >
> > In vprintk_emit() we do:
> >
> > if (!in_panic && printk_kthread) {
> > /* Offload printing to a schedulable context. */
> > need_flush_console = true;
> > wake_up_process(printk_kthread);
> > } else {
> > ...
> >
> > This guarantees that after message was appended to the buffer in
> > vprintk_emit(), the message got either printed by console_unlock() or
> > printk_kthread is in TASK_RUNNING state and will call console_unlock() once
> > scheduled. It also guarantees that printk_kthread_func() won't loop forever
> > when there's nothing to print. And that is all we need...
> >
> > I think the simplicity of this is worth the possible extra loops in
> > printk_kthread_func().
>
> I do not have strong opinion about this. I agree that the simplicity
> of your proposal is nice. You are much more experienced kernel
> developer. If you say that the potential extra loop is fine, I am
> fine with it as well :-)
>

works for me, re-sent.
the patch is even smaller now, and we almost have nothing else to
cut off from it :)

-ss