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From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Tony Luck <tony.luck@intel.com>,
	Frederic Weisbecker <fweisbec@gmail.com>,
	linux-kernel@vger.kernel.org, Greg KH <gregkh@suse.de>,
	Thomas Gleixner <tglx@linutronix.de>,
	Andrew Morton <akpm@linux-foundation.org>,
	John Kacur <jkacur@redhat.com>, Al Viro <viro@zeniv.linux.org.uk>,
	Ingo Molnar <mingo@elte.hu>
Subject: Re: [PATCH] serial: revert "Use block_til_ready helper"
Date: Sat, 19 Jun 2010 22:57:06 +0100	[thread overview]
Message-ID: <20100619225706.340eda52@lxorguk.ukuu.org.uk> (raw)
In-Reply-To: <201006192229.21971.arnd@arndb.de>

O> 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.

So the init code isn't getting run somewhere for some reason. Almost
certainly a count bug.

> Alan, any idea where the problem may be with the broken patch?

I'll take a look. We really don't want to revert this as it fixes some
nasty things the BKL covers over so I'd be worried the races would become
exposed (and it possibly allows NULL->func() calls if it can which would
be bad)

First guess would be something in port->count going astray and the port
not getting re-initialised.

Important question - does it need a getty or will a simple cat < /dev/foo
twice get garbled (or cat > if its garbling the other way)

Which direction matters and whether a hangup is needed matters

  reply	other threads:[~2010-06-19 21:54 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-05-15 20:59 [PATCH v3 00/10] BKL conversion in tty layer Arnd Bergmann
2010-05-15 20:59 ` [PATCH 01/10] tty: replace BKL with a new tty_lock Arnd Bergmann
2010-05-15 20:59 ` [PATCH 02/10] tty: never hold BTM while getting tty_mutex Arnd Bergmann
2010-05-15 20:59 ` [PATCH 03/10] tty: fix console_sem lock order Arnd Bergmann
2010-05-15 20:59 ` [PATCH 04/10] cdc-acm: remove dead code Arnd Bergmann
2010-05-15 20:59 ` [PATCH 05/10] tty: introduce wait_event_interruptible_tty Arnd Bergmann
2010-05-15 20:59 ` [PATCH 06/10] tty: annotate tty_write_lock Arnd Bergmann
2010-05-15 20:59 ` [PATCH 07/10] tty: reorder ldisc locking Arnd Bergmann
2010-05-15 20:59 ` [PATCH 08/10] tty: untangle locking of wait_until_sent Arnd Bergmann
2010-05-16  3:12   ` Daniel K.
2010-05-15 20:59 ` [PATCH 09/10] tty: remove tty_lock_nested Arnd Bergmann
2010-05-15 20:59 ` [PATCH 10/10] tty: implement BTM as mutex instead of BKL Arnd Bergmann
2010-05-16  3:33   ` Daniel K.
2010-05-16 12:58     ` Arnd Bergmann
2010-05-17 13:41 ` [PATCH v3 00/10] BKL conversion in tty layer Alan Cox
2010-05-17 15:30   ` Greg KH
2010-05-17 18:30     ` Arnd Bergmann
2010-05-18  4:27       ` Greg KH
2010-05-18 21:52         ` Arnd Bergmann
2010-05-19  1:50           ` Greg KH
2010-05-22 13:54             ` Arnd Bergmann
2010-05-17 18:49   ` Arnd Bergmann
2010-06-17 19:13   ` Tony Luck
2010-06-17 19:40     ` Arnd Bergmann
2010-06-17 20:15       ` Tony Luck
2010-06-17 21:48         ` Arnd Bergmann
2010-06-17 22:09           ` Frederic Weisbecker
2010-06-18 12:58             ` [PATCH] tty: avoid recursive BTM in pty_close Arnd Bergmann
2010-06-18 16:21               ` Alan Cox
2010-06-18 16:52                 ` Tony Luck
2010-06-18 18:35                   ` Arnd Bergmann
2010-06-18 20:25                     ` Tony Luck
2010-06-19 12:32                       ` Arnd Bergmann
2010-06-19 20:29                         ` [PATCH] serial: revert "Use block_til_ready helper" Arnd Bergmann
2010-06-19 21:57                           ` Alan Cox [this message]
2010-06-20 20:54                             ` Arnd Bergmann
2010-06-21 14:13                               ` Alan Cox
2010-06-21 20:57                                 ` Arnd Bergmann
2010-06-21 20:58                                   ` Arnd Bergmann
2010-06-21 17:11                           ` Tony Luck
2010-06-22 23:01                           ` Greg KH
2010-06-28 17:17                     ` [PATCH] tty: avoid recursive BTM in pty_close Tony Luck
2010-06-28 19:03                       ` Arnd Bergmann

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