From: Johan Hovold <johan@kernel.org>
To: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
Cc: Johan Hovold <johan@kernel.org>, Pavel Machek <pavel@ucw.cz>,
linux-serial@vger.kernel.org,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-kernel@vger.kernel.org,
Jacek Anaszewski <jacek.anaszewski@gmail.com>,
kernel@pengutronix.de, Jiri Slaby <jslaby@suse.com>,
linux-leds@vger.kernel.org, Dan Murphy <dmurphy@ti.com>
Subject: Re: [PATCH v7 3/3] leds: trigger: implement a tty trigger
Date: Wed, 22 Jul 2020 10:34:25 +0200 [thread overview]
Message-ID: <20200722083425.GF3634@localhost> (raw)
In-Reply-To: <20200721194815.mmkqccrkbgrly4xz@pengutronix.de>
[-- Attachment #1: Type: text/plain, Size: 1528 bytes --]
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
[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 228 bytes --]
prev parent reply other threads:[~2020-07-22 8:34 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-07 16:59 [PATCH v7 0/3] leds: trigger: implement a tty trigger Uwe Kleine-König
2020-07-07 16:59 ` [PATCH v7 1/3] tty: rename tty_kopen() and add new function tty_kopen_shared() Uwe Kleine-König
2020-07-07 16:59 ` [PATCH v7 2/3] tty: new helper function tty_get_icount() Uwe Kleine-König
2020-07-07 16:59 ` [PATCH v7 3/3] leds: trigger: implement a tty trigger Uwe Kleine-König
2020-07-12 8:24 ` Pavel Machek
2020-07-12 8:43 ` Greg Kroah-Hartman
2020-07-12 8:50 ` Pavel Machek
2020-07-12 9:02 ` Greg Kroah-Hartman
2020-07-12 9:07 ` Pavel Machek
2020-07-12 9:31 ` Greg Kroah-Hartman
2020-07-13 10:26 ` Uwe Kleine-König
2020-07-14 7:13 ` Johan Hovold
2020-07-21 19:48 ` Uwe Kleine-König
2020-07-22 8:34 ` Johan Hovold [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200722083425.GF3634@localhost \
--to=johan@kernel.org \
--cc=dmurphy@ti.com \
--cc=gregkh@linuxfoundation.org \
--cc=jacek.anaszewski@gmail.com \
--cc=jslaby@suse.com \
--cc=kernel@pengutronix.de \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-leds@vger.kernel.org \
--cc=linux-serial@vger.kernel.org \
--cc=pavel@ucw.cz \
--cc=u.kleine-koenig@pengutronix.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).