g_dbgp + u_serial: WARNING when unloading g_dbgp module

[Randy Dunlap <rdunlap@xxxxxxxxxxxxx>]

Linux v5.0-11053-gebc551f2b8f9 of March 12, on x86_64:

with
CONFIG_USB_G_DBGP=m
# CONFIG_USB_G_DBGP_PRINTK is not set
CONFIG_USB_G_DBGP_SERIAL=y
CONFIG_USB_U_SERIAL=m

Loading g_dbgp module and then unloading it causes:

WARNING: CPU: 0 PID: 24523 at ../drivers/usb/gadget/function/u_serial.c:1195 gserial_free_line+0x161/0x2b0 [u_serial]


Is that expected?

thanks.
-- 
~Randy