linux-kernel - Re: [PATCH] tty: Add driver unthrottle in ioctl(...,TCFLSH,..).

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Date:	Thu, 22 Nov 2012 01:39:13 +0400
From:	Ilya Zykov <ilya@...x.ru>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
CC:	linux-kernel@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Andrew McGregor <andrew.mcgregor@...iedtelesis.co.nz>
Subject: Re: [PATCH] tty: Add driver unthrottle in ioctl(...,TCFLSH,..).

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)

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