linux-kernel - Re: [PATCH] tty: avoid recursive BTM in pty

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Message-ID: <AANLkTim4dHj_3ftAVD35DD-Cc7ZntHRi1YTRPup2wfJc@mail.gmail.com>
Date:	Fri, 18 Jun 2010 13:25:22 -0700
From:	Tony Luck <tony.luck@...el.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Frederic Weisbecker <fweisbec@...il.com>,
	linux-kernel@...r.kernel.org, Greg KH <gregkh@...e.de>,
	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] tty: avoid recursive BTM in pty_close

On Fri, Jun 18, 2010 at 11:35 AM, Arnd Bergmann <arnd@...db.de> wrote:
> Ok, this is the same one you reported at first. I forgot to
> mention that the other patch I sent as a reply to your report
> is still needed and not yet in -next since I'm trying to
> sort through the other BKL removal patches now.
> This instance of the WARN_ON is completely harmless though,
> you could consider this one a false positive.

Ok. Adding your first patch into todays mix cleaned away
these messages,

> Do you know if this was a problem with the original series or
> something that got introduced by my last patch?

Problem was there before. Looks like it was not in next-20100616
but began with next-20100617.

> Also, if you don't mind, could you try if the problem also exists
> with CONFIG_TTY_MUTEX enabled?
With CONFIG_TTY_MUTEX=y kernel with both your patches builds
and boots with no unusual messages.  Application output still gets
garbled.

> Which serial driver do you use?
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.

-Tony
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