From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from coco.kroah.org (kroah.org [198.145.64.141]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (Client CN "coco.kroah.org", Issuer "Greg KH" (not verified)) by ozlabs.org (Postfix) with ESMTPS id 36A461007DA for ; Thu, 21 Apr 2011 00:34:06 +1000 (EST) Date: Wed, 20 Apr 2011 07:34:35 -0700 From: Greg KH To: Amit Shah Subject: Re: hvc_console: Don't access hvc_task if not initialised Message-ID: <20110420143435.GB22436@kroah.com> References: <20110325084714.GA28356@amit-x200.redhat.com> <20110420123330.GB3519@amit-x200.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20110420123330.GB3519@amit-x200.redhat.com> Cc: Rusty Russell , linux-kernel@vger.kernel.org, Milton Miller , linuxppc-dev@ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, Apr 20, 2011 at 06:03:30PM +0530, Amit Shah wrote: > On (Mon) 28 Mar 2011 [11:52:05], Milton Miller wrote: > > On Fri, 25 Mar 2011 about 14:17:14 +0530, Amit Shah wrote: > > > On (Thu) 24 Mar 2011 [08:58:04], Milton Miller wrote: > > > > On Thu, 24 Mar 2011 07:29:58 -0000, Amit Shah wrote: > > > > > hvc_open() can be called without having any backing device. This > > > > > results in a call to hvc_kick() which calls wake_up_process on a NULL > > > > > pointer. > > > > > > > > How is hvc_open called without a hvc_driver registered to the tty layer? > > > > > > This gets reproduced in a couple of scenarios, I'm trying to get more > > > information. > > OK - I finally could reproduce myself, albiet it's a panic in > hvc_open, not the one mentioned earlier. > > hvc_console is built into the kernel and virtio_console is a module. > This sequence triggers a panic: > > - modprobe virtio_console > - agetty /dev/hvc0 9600 vt100 > - rmmod virtio_console > - modprobe virtio_console > - agetty /dev/hvc0 9600 vt100 > > A patch that I had sent previously, to hvc_remove() a port when the > associated virtio_console port gets unplugged, fixes this panic. > > Stricter checking in hvc_open(), as you mentioned, will solve the > other one as well. Care to either create this patch, or resend your original one, if you want it applied? thanks, greg k-h