From: "andrew mcgregor" <andrew.mcgregor@alliedtelesis.co.nz>
To: "Ilya Zykov" <ilya@ilyx.ru>, "Alan Cox" <alan@lxorguk.ukuu.org.uk>
Cc: "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] tty: Add driver unthrottle in ioctl(...,TCFLSH,..).
Date: Thu, 22 Nov 2012 13:47:15 +1300 [thread overview]
Message-ID: <50AE2CE30200003600026B9A@gwia.alliedtelesyn.co.nz> (raw)
In-Reply-To: <50AD4A01.7060500@ilyx.ru>
>>> On 11/22/2012 at 10:39 AM, in message <50AD4A01.7060500@ilyx.ru>, Ilya Zykov
<ilya@ilyx.ru> wrote:
> On 22.11.2012 1:30, Alan Cox wrote:
> >> Function reset_buffer_flags() also invoked during the
> >> ioctl(...,TCFLSH,..). At the time of request we can have full buffers
> >> and throttled driver too. If we don't unthrottle driver, we can get
> >> forever throttled driver, because after request, we will have
> >> empty buffers and throttled driver and there is no place to unthrottle
> driver.
> >> It simple reproduce with "pty" pair then one side sleep on tty->write_wait,
> >> and other side do ioctl(...,TCFLSH,..). Then there is no place to do
> writers wake up.
> >
> >
> > So instead of revertng it why not just fix it ? Just add an argument to
> > the reset_buffer_flags function to indicate if unthrottling is permitted.
> >
> > Alan
> >
> Because in my opinion, unthrottling permitted always, except release
> last filp (tty->count == 0)
Maybe so, but the patch was there in the first place to resolve an actual observed bug, where a driver would lock up. So the behaviour needs preserved.
Andrew
next prev parent reply other threads:[~2012-11-22 19:34 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-21 21:12 [PATCH] tty: Add driver unthrottle in ioctl(...,TCFLSH,..) Ilya Zykov
2012-11-21 21:30 ` Alan Cox
2012-11-21 21:39 ` Ilya Zykov
2012-11-22 0:47 ` andrew mcgregor [this message]
2012-11-22 4:29 ` Ilya Zykov
2012-11-22 5:25 ` andrew mcgregor
2012-11-22 6:35 ` Ilya Zykov
2012-11-22 6:03 ` Ilya Zykov
2012-11-22 6:16 ` Ilya Zykov
2012-11-21 21:55 ` Ilya Zykov
2012-11-27 6:14 [PATCH v4] " Ilya Zykov
2012-11-27 17:24 ` Greg Kroah-Hartman
2012-11-27 18:46 ` Ilya Zykov
2012-11-27 19:32 ` Alan Cox
2013-01-16 9:07 ` [PATCH] " Ilya Zykov
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