linux-kernel - Re: [PATCH] serial: revert "Use block_til

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Date:	Tue, 22 Jun 2010 16:01:13 -0700
From:	Greg KH <gregkh@...e.de>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Tony Luck <tony.luck@...el.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Frederic Weisbecker <fweisbec@...il.com>,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	John Kacur <jkacur@...hat.com>,
	Al Viro <viro@...iv.linux.org.uk>, Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH] serial: revert "Use block_til_ready helper"

On Sat, Jun 19, 2010 at 10:29:21PM +0200, Arnd Bergmann wrote:
> On Saturday 19 June 2010 14:32:04 Arnd Bergmann wrote:
> > > I boot with a "console=uart,io,0x3f8" argument, so I start out using
> > > 8250_early.c. Looks like it switched to 8250.c based on seeing
> > > this:
> > > 
> > > Serial: 8250/16550 driver, 4 ports, IRQ sharing enabled
> > > 
> > > on the console log.
> > 
> > Good, so it's something I should be able to reproduce on a PC.
> 
> I could reproduce the problem now and bisected it down to a cleanup
> patch that can fortunately get reverted. The symptom that I saw
> is that when I open a serial port for the second time (e.g. starting
> getty and logging in), the output gets garbled, while the first one
> worked fine. This does not rely on the console code at all.
> 
> Original commit message:
>     Our code now rather closely resembles the helper, so switch to it.
> 
> Apparently, the two functions are not really doing the same,
> so revert the commit for now. This includes the addition of
> a tty_unlock()/tty_lock() pair when blocking on the wait queue.
> 
> Greg, do you want to apply this patch on top of the series, or
> do you prefer to get a replacement for the original patch, once
> we know what's wrong with it?

A replacement for the original one might be best if we can figure it
out.

Just let me know what you need me to do.

thanks,

greg k-h
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