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From: Jiri Slaby <jslaby@suse.cz>
To: Havard Skinnemoen <hskinnemoen@google.com>
Cc: Jiri Slaby <jirislaby@gmail.com>, Dave Jones <davej@redhat.com>,
	Linux Kernel <linux-kernel@vger.kernel.org>,
	Greg Kroah-Hartman <gregkh@suse.de>,
	Alan Cox <alan@linux.intel.com>
Subject: Re: [RFC] cdc-acm: Fix potential deadlock (lockdep warning)
Date: Wed, 23 Nov 2011 20:55:57 +0100	[thread overview]
Message-ID: <4ECD4FCD.7040602@suse.cz> (raw)
In-Reply-To: <1322074412-10873-1-git-send-email-hskinnemoen@google.com>

On 11/23/2011 07:53 PM, Havard Skinnemoen wrote:
> --- a/drivers/usb/class/cdc-acm.c
> +++ b/drivers/usb/class/cdc-acm.c
...
> @@ -567,19 +574,10 @@ static void acm_tty_close(struct tty_struct *tty, struct file *filp)
>  
>  	/* Perform the closing process and see if we need to do the hardware
>  	   shutdown */
> -	if (!acm)
> -		return;
> -
> -	mutex_lock(&open_mutex);
>  	if (tty_port_close_start(&acm->port, tty, filp) == 0) {

Note that port->count is protected by port->lock usually. Till now it
used to be protected by open_mutex in your driver. As of now it is not
protected by anything. (Well, BTM is still there to save you, but...)

thanks,
-- 
js
suse labs

  parent reply	other threads:[~2011-11-23 19:56 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-11-23  3:38 tty related lockdep trace during bootup on 3.2-rc2 Dave Jones
2011-11-23  7:28 ` Havard Skinnemoen
2011-11-23  7:39   ` Cong Wang
2011-11-23 10:12   ` Jiri Slaby
2011-11-23 10:14     ` Jiri Slaby
2011-11-23 17:58     ` Havard Skinnemoen
2011-11-23 18:53       ` [RFC] cdc-acm: Fix potential deadlock (lockdep warning) Havard Skinnemoen
2011-11-23 19:22         ` Alan Cox
2011-11-23 19:22           ` Havard Skinnemoen
2011-11-23 19:44             ` Alan Cox
2011-11-23 21:03               ` Havard Skinnemoen
2011-11-23 21:59                 ` Alan Cox
2011-11-23 19:34           ` Oliver Neukum
2011-11-23 22:00             ` Alan Cox
2011-11-23 19:55         ` Jiri Slaby [this message]
2011-11-23 21:08           ` Havard Skinnemoen
2011-11-23 21:11             ` Jiri Slaby
2011-11-23 21:19               ` Jiri Slaby
2011-11-27 21:37         ` [RFC v2] " Havard Skinnemoen
2011-11-28 18:15           ` Havard Skinnemoen
2011-11-23  7:29 ` tty related lockdep trace during bootup on 3.2-rc2 Cong Wang
2011-11-23 17:29   ` Havard Skinnemoen

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