Network manager automatically changes my wireless monitor interfaces to managed interfaces. This makes it possible to use monitor interfaces together with network-manager. Also the created monitor interfaces have the same mac addresses as the wlan0 devices and thus the automatically started wpa_supplicant goes crazy and takes all the CPU time of one core and prints following things to the syslog:

NetworkManager[2875]: <error> [1413475379.075720] [supplicant-manager/nm-supplicant-interface.c:856] interface_add_cb(): (moni0): error adding interface: wpa_supplicant couldn't grab this interface.


The monitor interface is created on a T420 with following command:

$ iw phy phy0 interface add moni0 type monitor flags control

It results in following state (it should be monitor and not managed):

$ sudo iw dev
phy#0
        Interface moni0
                ifindex 7
                wdev 0x5
                addr 02:23:45:67:89:01
                type managed
        Interface wlan0
                ifindex 3
                wdev 0x1
                addr 02:23:45:67:89:01
                type managed
                channel 48 (5240 MHz), width: 20 MHz, center1: 5240 MHz

This problem can only be fixed by disabling the network-manager (!!!!!), deleting the moni0 device and creating it again.
Debian Release: jessie/sid
  500 unstable        http.debian.net
--- Package information. ---
Depends                         (Version) | Installed
=========================================-+-================
libc6                           (>= 2.17) |
libdbus-1-3                    (>= 1.0.2) |
libdbus-glib-1-2               (>= 0.102) |
libgcrypt11                    (>= 1.4.5) |
libglib2.0-0                  (>= 2.37.3) |
libgnutls-deb0-28           (>= 3.2.10-0) |
libgudev-1.0-0                   (>= 165) |
libmm-glib0                    (>= 1.0.0) |
libndp0                          (>= 1.2) |
libnewt0.52                               |
libnl-3-200                   (>= 3.2.21) |
libnl-genl-3-200              (>= 3.2.21) |
libnl-route-3-200              (>= 3.2.7) |
libnm-glib4                 (>= 0.9.10.0) |
libnm-util2                 (>= 0.9.10.0) |
libpolkit-gobject-1-0          (>= 0.101) |
libreadline6                     (>= 6.0) |
libsoup2.4-1                  (>= 2.39.3) |
libsystemd-daemon0                (>= 31) |
libsystemd-login0                 (>= 31) |
libuuid1                        (>= 2.16) |
init-system-helpers            (>= 1.18~) |
lsb-base                      (>= 3.2-14) |
wpasupplicant                (>= 0.7.3-1) |
dbus                           (>= 1.1.2) |
udev                                      |
adduser                                   |
isc-dhcp-client           (>= 4.1.1-P1-4) |
libpam-systemd                            |
policykit-1                               |


Recommends        (Version) | Installed
===========================-+-===========
ppp              (>= 2.4.6) | 2.4.6-2
dnsmasq-base                | 2.72-2
iptables                    | 1.4.21-2
modemmanager                | 1.4.0-1
crda                        | 3.13-1


Suggests           (Version) | Installed
============================-+-===========
avahi-autoipd                | 0.6.31-4