From: Dan Drown <dan-netdev@drown.org>
To: Oliver Neukum <oneukum@suse.com>
Cc: linux-usb@vger.kernel.org
Subject: Re: [PATCH] usb: cdc-acm: add PPS support
Date: Wed, 16 Aug 2023 09:17:04 -0500 [thread overview]
Message-ID: <ZNzaYJ7CC/G280ct@vps3.drown.org> (raw)
In-Reply-To: <cf57f9ef-90f4-7ef5-405e-78f79007f7bc@suse.com>
On Wed, Aug 16, 2023 at 11:50:15AM +0200, Oliver Neukum wrote:
> On 15.08.23 03:02, Dan Drown wrote:
> > Looks like it was put there to protect the iocount changes in the
> > surrounding code. Are your concerns around performance or deadlocks?
>
> the lock is there for that and so that wait_serial_change()
> will read consistent counts.
>
> The latter concerns me. We are calling potentially arbitrary code. That
> you intend it for PPS doesn't change that we'll call it for
> every line discipline that supports that callback.
> Line disciplines are supposed to do something with tty devices,
> aren't they? So what methods could they call in turn?
> Something that can end in wait_serial_change()?
Looking at the callers of tty_register_ldisc, the only one that passes
in a dcd_change handler is the pps-ldisc. That's not to say that
couldn't change in the future.
I could move the call to dcd_change before the read lock is acquired,
would that work for you?
next prev parent reply other threads:[~2023-08-16 14:18 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-06 2:26 [PATCH] usb: cdc-acm: add PPS support Dan Drown
2023-08-14 12:32 ` Oliver Neukum
2023-08-15 1:02 ` Dan Drown
2023-08-16 9:50 ` Oliver Neukum
2023-08-16 14:17 ` Dan Drown [this message]
2023-08-16 19:58 ` Oliver Neukum
2023-08-17 1:09 ` [PATCH] usb: cdc-acm: move ldisc dcd notification outside of acm's read lock Dan Drown
2023-08-17 8:19 ` Oliver Neukum
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=ZNzaYJ7CC/G280ct@vps3.drown.org \
--to=dan-netdev@drown.org \
--cc=linux-usb@vger.kernel.org \
--cc=oneukum@suse.com \
/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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.