usb/113964: [patch] ucom(4): kernel panic when dropping a connection

[Kazuaki ODA]

The following reply was made to PR usb/113964; it has been noted by GNATS.

From: Kazuaki ODA <kazuaki at aliceblue.jp>
To: "M. Warner Losh" <imp at bsdimp.com>
Cc: FreeBSD-gnats-submit at FreeBSD.ORG
Subject: Re: usb/113964: [patch] ucom(4): kernel panic when dropping a connection
Date: Sun, 24 Jun 2007 04:56:22 +0900

 M. Warner Losh wrote:
 > In message: <200706231136.l5NBa61H001748 at eyes.aliceblue.jp>
 >             Kazuaki ODA <kazuaki at aliceblue.jp> writes:
 > : 	I don't know the proper fix but the following patch is workaround for
 > : 	me.
 > : 
 > : --- ucom.c.patch begins here ---
 > : --- sys/dev/usb/ucom.c.orig	2007-06-22 23:45:37.000000000 +0900
 > : +++ sys/dev/usb/ucom.c	2007-06-23 17:47:18.000000000 +0900
 > : @@ -532,6 +532,9 @@
 > :  	if (sc->sc_dying)
 > :  		return;
 > :  
 > : +	if (sc->sc_oxfer == NULL)
 > : +		return;
 > : +
 > :  	s = spltty();
 > :  
 > :  	if (tp->t_state & TS_TBLOCK) {
 > : --- ucom.c.patch ends here ---
 > 
 > This is a good workaround.  However, why does the tty->t_oproc get
 > called after the tty->t_close routine which sets sc->sc_oxfer to NULL?
 > 
 > Warner
 
 Unfortunately, I have no idea.  But it seems the changes of tty 
 subsystem and ucom.c rev. 1.56 are related to the issue.
 
 * On 5.x-RELEASE, where ucom.c rev. 1.56 has been MFCed, we get no panic.
 
 * On 6.x-RELEASE or 7.0-CURRENT, we get a panic.
 
 * After backing out ucom.c rev. 1.56, no panic on 6.x-RELEASE or 
 7.0-CURRENT.
 
 -- 
 Kazuaki ODA