From: Arnd Bergmann <arnd@arndb.de>
To: Jiri Slaby <jslaby@suse.cz>
Cc: gregkh@suse.de, alan@linux.intel.com,
Linux kernel mailing list <linux-kernel@vger.kernel.org>
Subject: Re: patch "TTY: remove tty_locked" added to tty tree
Date: Wed, 24 Aug 2011 10:46:30 +0200 [thread overview]
Message-ID: <73013289.R6WJLciOm2@wuerfel> (raw)
In-Reply-To: <4E53F750.2050408@suse.cz>
On Tuesday 23 August 2011 20:54:08 Jiri Slaby wrote:
> On 08/23/2011 08:46 PM, Arnd Bergmann wrote:
> > According to http://kernelnewbies.org/BigKernelLock, I concluded back then
> > that tty_wait_until_sent would always be called without BTM held. Has that
> > changed recently, or did I miss a caller that holds the BTM?
>
> Every tty_operations->close and ->hangup :).
Ah, right, I remember. The chart I did was only to prove that locking was
consistent (i.e. no deadlocks), it ignored that the function needs to be
called without BTM because I had incorrectly convinced myself that the
wait_event_interruptible_timeout() didn't need to release it.
I think I just saw another problem: uart_close takes port->mutex while
holding the BTM, then calls tty_wait_until_sent(). If this releases
and reaquires the BTM, you get an AB-BA deadlock with port->mutex.
Arnd
next prev parent reply other threads:[~2011-08-24 8:47 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <13141210141189@kroah.org>
2011-08-23 18:33 ` Jiri Slaby
2011-08-23 18:46 ` Arnd Bergmann
2011-08-23 18:54 ` Jiri Slaby
2011-08-24 8:46 ` Arnd Bergmann [this message]
2011-08-24 9:31 ` Jiri Slaby
2011-08-24 11:20 ` Arnd Bergmann
2011-08-24 11:47 ` Jiri Slaby
2011-08-24 14:35 ` Arnd Bergmann
2011-08-24 21:27 ` Jiri Slaby
2011-08-24 21:42 ` Greg KH
2011-08-24 21:48 ` Jiri Slaby
2011-08-24 21:54 ` Greg KH
2011-08-25 13:12 ` [PATCH 1/5] TTY: serial, use ASYNCB_CLOSING in uart_close Jiri Slaby
2011-08-25 13:12 ` [PATCH 2/5] TTY: serial, move locking " Jiri Slaby
2011-08-25 13:12 ` [PATCH 3/5] TTY: define tty_wait_until_sent_from_close Jiri Slaby
2011-08-25 13:12 ` [PATCH 4/5] TTY: use tty_wait_until_sent_from_close in tty_port_close_start Jiri Slaby
2011-08-25 13:12 ` [PATCH 5/5] TTY: use tty_wait_until_sent_from_close in other drivers Jiri Slaby
2011-08-25 15:15 ` [PATCH 1/5] TTY: serial, use ASYNCB_CLOSING in uart_close Arnd Bergmann
2011-08-24 15:53 ` patch "TTY: remove tty_locked" added to tty tree Alan Cox
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