From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg KH Date: Mon, 14 Mar 2016 17:49:01 +0000 Subject: Re: How to determine which device crashes udev in boot? Message-Id: <20160314174901.GA27275@kroah.com> List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-hotplug@vger.kernel.org On Mon, Mar 14, 2016 at 01:48:39PM +0900, iwillallways forget1 wrote: > I'm trying to narrow which device in an NEC VF-6 causes Linux boots to > hang, permanently, in udevadm trigger and udevadm settle. Many Google > searches found many pages but no tutorials on how to debug udev this > way. > > I downloaded fresh copies of Porteus 3.1 32-bit and 64-bit. What kernel versions are these? > Porteus 3.1 64-bit boots fine, udev finds everything, x Windows works > (I told you Windows rulez), etc. Even on this NEC VF-6. > > Porteus 3.1 32-bit boots fine on everything except this NEC VF-6, x > Windows works, etc. > > Porteus 3.1 32-bit hangs when starting udev on this NEC VF-6. It's > not a 120-second timeout in udevadm settle. It never wakes up. The > Caps Lock key stops toggling the Caps Lock light. The Num Lock key > stops toggling the Num Lock light. Ctrl+Alt+Delete is ignored. It > does not appear to be a kernel panic because two of the keyboard > lights don't flash. It is hanged, frozen, dead. > > Booting with "3 nohotplug" works (3 tells Porteus what run level to > use, and nohotplug is observed by both the kernel and Porteus). In > text mode I can do some amount of experiments. I don't know how to do > meaningful experiments, to try to track down which device causes the > hang. Try looking at the documentation of udevadm, you can manually enable the 'coldplug' options there to narrow down what hardware is causing the problem. Odds are, you have a kernel driver that doesn't like the hardware and it is getting loaded automatically by udev. good luck! greg k-h