On Fri, Mar 15, 2024 at 01:06:33PM -0400, Alan Stern wrote: > The show and store callback routines for the "disable" sysfs attribute > file in port.c acquire the device lock for the port's parent hub > device. This can cause problems if another process has locked the hub > to remove it or change its configuration: > > Removing the hub or changing its configuration requires the > hub interface to be removed, which requires the port device > to be removed, and device_del() waits until all outstanding > sysfs attribute callbacks for the ports have returned. The > lock can't be released until then. > > But the disable_show() or disable_store() routine can't return > until after it has acquired the lock. > > The resulting deadlock can be avoided by calling > sysfs_break_active_protection(). This will cause the sysfs core not > to wait for the attribute's callback routine to return, allowing the > removal to proceed. The disadvantage is that after making this call, > there is no guarantee that the hub structure won't be deallocated at > any moment. To prevent this, we have to acquire a reference to it > first by calling hub_get(). > > Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> > Cc: <stable@xxxxxxxxxxxxxxx> # Needs the previous patch in this series What "previous patch"? I don't see this as a series even on lore.kernel.org. confused, greg k-h
