linux-kernel - Re: [PATCH] USB: ftdi_sio: Remove tty->low

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Message-ID: <m1ske1wgdi.fsf@fess.ebiederm.org>
Date:	Fri, 02 Oct 2009 16:00:41 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Johan Hovold <jhovold@...il.com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Michael Trimarchi <trimarchi@...dalf.sssup.it>,
	Oliver Neukum <oliver@...kum.org>, linux-usb@...r.kernel.org,
	Alan Cox <alan@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] USB: ftdi_sio: Remove tty->low_latency.



I have seen a hang in:
  /bin/stty (changing the baud rate)
    set_termios
      tty_wait_until_sent
        tty_chars_in_buffer
          ftdi_chars_in_buffer

Where the driver wedged for a serial port and no progress
was made.

This happened to me several times with 2.6.31.  My initial
hypothesis was this was a hardware error (as it only happened
on single piece of hardware).  With all of the driver problems
I suspect it could be a driver bug.

Any ideas from the people who understand this code?

Eric
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