On Wed, Mar 15, 2006 at 10:24:49AM -0600, Paul Fulghum wrote:
> On Wed, 2006-03-15 at 09:34 +0100, Oliver Neukum wrote:
> > > hub 1-0:1.0: debounce: port 2: total 100ms stable 100ms status 0x100
> > > acm_tty_unregister if=cee8896c dev=cee88980 ref=2
> > > class_device_del call sysfs_remove_link class_dev=c9a6aec4 ref=2
> > > dentry=c8f7a2b4
> > > class_device_del call sysfs_remove_link class_dev->dev=cee88980 ref=1
> > > dentry=ceaaa1a4 class_name=tty:ttyACM0
> > > sysfs_hash_and_remove dir=ceaaa1a4 d_inode=6b6b6b6b
> >
> > sysfs_hash_and_remove() is called for a freed dentry. This is from the
> > second
> > call in class_device_del().
>
> This is becoming clearer:
>
> 1. usb device is disconnected (usb/core/hub.c:usb_disconnect)
> 2. usb_disconnect calls usb_disconnect recursively for child devices
> 3. usb_disconnect calls drivers/base/core.c:device_unregister() for dev
> 4. device_unregister() -> device_del() -> device_remove_file()
It only calls device_remove_file for the uevent file. Not anything
else (like the symlink).
> void device_remove_file(struct device * dev, struct device_attribute * attr)
> {
> if (get_device(dev)) {
> sysfs_remove_file(&dev->kobj, &attr->attr);
> put_device(dev);
> }
> }
>
> The sysfs entry is deleted, which appears to release dev->kobj->dentry
> even though dev->kobj is still valid with references.
What sysfs entry? Ah, with the call to sysfs_remove_dir() Yes, we
remove them all.
Ok, this is the problem right here. Now, how has this ever worked in
the past? Why don't cdc-acm devices with the other configuration not
also cause this issue?
Looks like we should try unregistering the tty device here, in the
disconnect. I wonder how bad that will cause the tty layer to oops...
thanks,
greg k-h
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