linux-kernel - RE: [PATCH] serial: 8250: Add cpufreq support

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Date:	Tue, 17 Apr 2012 09:43:30 +0000
From:	"Shankarmurthy, Akshay" <akshay.s@...com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
CC:	"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
	"alan@...ux.intel.com" <alan@...ux.intel.com>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"paul.gortmaker@...driver.com" <paul.gortmaker@...driver.com>,
	"jamie@...ieiles.com" <jamie@...ieiles.com>,
	"swarren@...dia.com" <swarren@...dia.com>,
	"dianders@...omium.org" <dianders@...omium.org>,
	"davinci-linux-open-source@...ux.davincidsp.com" 
	<davinci-linux-open-source@...ux.davincidsp.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] serial: 8250: Add cpufreq support

On Thu, Apr 12, 2012 at 15:17:58, Alan Cox wrote:
> > > > I will have a look at this and add the lock if necessary.
> > > 
> > > At the very least you need reference counts held on the tty struct and to allow for the tty having vanished under you.
> > > 
> > 
> > I am planning to add "tty->termios_mutex" lock. Any comments ?
> 
> Explain how this will help. You need a reference count to the tty itself.
> 


I have gone through the serial driver, still I am not able to figure out the requirement
of tty reference count here. Correct me if I am wrong. 
As per my understanding, tty count keeps the count of tty_open and tty_release, that is
how many open and close happened on the tty device file(/dev/ttyS*).
The requirement here is a tty count check, if it is greater than zero then only it should
proceed for further execution. 
Kindly elaborate more on the same if it's not correct.

> 
> Alan
> 

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