On Fri, 25 Mar 2005 10:22:28 +0100, Stefan Seyfried <[email protected]> wrote:
> Andy Isaacson wrote:
>
> > In the SysRq-T trace I see one interesting process: most things are
> > in D state in refrigerator(), but sh shows the following traceback:
> >
> > wait_for_completion
> > call_usermodehelper
> > kobject_hotplug
> > kobject_del
> > class_device_del
> > class_device_unregister
> > mousedev_disconnect
> > input_unregister_device
> > alps_disconnect
> > psmouse_disconnect
> > serio_driver_remove
> > device_release_driver
> > serio_release_driver
>
> i think the following happens (but i am in no case an expert for this):
> - alps driver suspends
> - alps driver unregisters the device
> - udev is called via call_usermodehelper (which fails since userspace
> is stopped)
> - now somebody wants to wait for udev which does not work right.
The thing is that kobject_uevent calls call_usermodehelper with
wait=0. That means that it conly waits for execve("/sbin/hotplug")
call to complete, it does not wait for the entire process ti complete.
If you look at Andy's second trace you will see that we are waiting
for the disk I/O to get /sbin/hotplug from the disk. Pavel, do you
know why IO does not complete? khelper is a kernel thread so it is
marked with
PF_NOFREEZE. Could it be that we managed to freeze kblockd?
--
Dmitry
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