From: Arnd Bergmann <arnd@arndb.de>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: LKML <linux-kernel@vger.kernel.org>, Greg KH <gregkh@suse.de>,
Frederic Weisbecker <fweisbec@gmail.com>,
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: [RFC 0/9] BKL conversion in TTY drivers
Date: Wed, 31 Mar 2010 09:57:02 +0200 [thread overview]
Message-ID: <201003310957.03025.arnd@arndb.de> (raw)
In-Reply-To: <20100330233759.00877e80@lxorguk.ukuu.org.uk>
On Wednesday 31 March 2010 00:37:59 Alan Cox wrote:
>
> > This means we are still safe, because there is no code
> > left that the new BTM fails to serialize with.
>
> We hope. I'm currently poking at sorting out the locking properly and
> quite frankly the locking rules for the current tty reference have me
> baffled. It clearly works as we've not got a pile of dumps in the
> bugzilla tree but its also quite a mystery *how*.
Yes, that's why I didn't even attempt to find out why the BKL is
in some places or what it protects, but only changed the way it gets
taken and released.
We also have empirical evidence that turning the BKL into a semaphore
doesn't make the code fall apart, so I'm assuming that the mutex based
implementation with the explicit release-when-blocking instead of
implicit release-when-sleeping is still equivalent.
Are you more worried that the interface conversion (patches 1-8)
can introduce bugs and make your life harder, or that the mutex
based implementation from patch 9 causes problems that were previously
hidden by other bugs?
Arnd
next prev parent reply other threads:[~2010-03-31 7:57 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-30 20:56 [RFC 0/9] BKL conversion in TTY drivers Arnd Bergmann
2010-03-30 20:56 ` [RFC 1/9] tty: replace BKL with a new tty_lock Arnd Bergmann
2010-03-30 22:23 ` Frederic Weisbecker
2010-03-30 20:56 ` [RFC 2/9] tty: make atomic_write_lock release tty_lock Arnd Bergmann
2010-03-30 20:56 ` [RFC 3/9] tty: make tty_port->mutex nest under tty_lock Arnd Bergmann
2010-03-30 20:56 ` [RFC 4/9] tty: make termios mutex " Arnd Bergmann
2010-03-30 20:56 ` [RFC 5/9] tty: make ldisc_mutex " Arnd Bergmann
2010-03-30 20:56 ` [RFC 6/9] tty: never hold tty_lock() while getting tty_mutex Arnd Bergmann
2010-03-30 20:56 ` [RFC 7/9] ppp: use big tty mutex Arnd Bergmann
2010-03-31 4:37 ` Américo Wang
2010-03-31 7:39 ` Arnd Bergmann
2010-03-30 20:56 ` [RFC 8/9] tty: release tty lock when blocking Arnd Bergmann
2010-03-30 20:56 ` [RFC 9/9] tty: implement BTM as mutex instead of BKL Arnd Bergmann
2010-03-30 22:50 ` Frederic Weisbecker
2010-03-30 22:37 ` [RFC 0/9] BKL conversion in TTY drivers Alan Cox
2010-03-31 7:57 ` Arnd Bergmann [this message]
2010-03-31 10:02 ` Alan Cox
2010-04-01 12:51 ` Arnd Bergmann
2010-04-01 14:17 ` Alan Cox
2010-04-01 15:24 ` Greg KH
2010-04-01 19:10 ` Arnd Bergmann
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