On Tue, Jul 21, 2020 at 09:48:15PM +0200, Uwe Kleine-König wrote:
> Hello Johan,
>
> On Tue, Jul 14, 2020 at 09:13:55AM +0200, Johan Hovold wrote:
> > On Tue, Jul 07, 2020 at 06:59:58PM +0200, Uwe Kleine-König wrote:
> > > + while (firstrun ||
> > > + icount.rx != trigger_data->rx ||
> > > + icount.tx != trigger_data->tx) {
> > > +
> > > + led_set_brightness(trigger_data->led_cdev, LED_ON);
> > > +
> > > + msleep(100);
> > > +
> > > + led_set_brightness(trigger_data->led_cdev, LED_OFF);
> > > +
> > > + trigger_data->rx = icount.rx;
> > > + trigger_data->tx = icount.tx;
> > > + firstrun = false;
> > > +
> > > + ret = tty_get_icount(trigger_data->tty, &icount);
> > > + if (ret)
> > > + return;
> > > + }
> >
> > Haven't looked at the latest proposal in detail, but this looks broken
> > as you can potentially loop indefinitely in a worker thread, and with no
> > way to stop the trigger (delayed work).
>
> I don't think that potentially looping indefinitely is a problem, but
> indeed it should drop the lock during each iteration. Will think about
> how to adapt.
You musn't queue work that can run for long on the global shared
workqueue as it affects flushing:
* system_wq is the one used by schedule[_delayed]_work[_on]().
* Multi-CPU multi-threaded. There are users which expect relatively
* short queue flush time. Don't queue works which can run for too
* long.
Work that potentially run indefinitely is an absolute no-no. :)
Johan
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