This patch (as1229) fixes a few lifetime and locking problems in the
usb-serial driver. The main symptom is that an invalid kevent is
created when the serial device is unplugged while a connection is
active.
Ports should be unregistered when device is disconnected,
not when the parent usb_serial structure is deallocated.
Each open file should hold a reference to the corresponding
port structure, and the reference should be released when
the file is closed.
serial->disc_mutex should be acquired in serial_open(), to
resolve the classic race between open and disconnect.
serial_close() doesn't need to hold both serial->disc_mutex
and port->mutex at the same time.
Release the subdriver's module reference only after releasing
all the other references, in case one of the release routines
needs to invoke some code in the subdriver module.
Replace a call to flush_scheduled_work() (which is prone to
deadlocks) with cancel_work_sync(). Also, add a call to
cancel_work_sync() in the disconnect routine.
Reduce the scope of serial->disc_mutex in serial_disconnect().
The only place it really needs to protect is where the
"disconnected" flag is set.
This fixes the bug reported in
http://bugs.freedesktop.org/show_bug.cgi?id=20703
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Tested-by: Dan Williams <dcbw@redhat.com>
Tested-by: Ming Lei <tom.leiming@gmail.com>
Reviewed-by: Oliver Neukum <oliver@neukum.org>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2d93148ab6