Opening a bug per request.  Discussed 

http://marc.info/?l=linux-wireless&m=136381302428113&w=2

and

http://marc.info/?l=linux-wireless&m=136416984531380


-------------------

I'm seeing a problem with the carl driver.  If I change channels
repeatedly on the 2.4ghz band, monitoring (e.g. tcpdump) will
eventually halt.  I've seen this on various versions of the carl
driver/firmware (both from 1.9.4 to 1.9.7)

After monitoring has hung, changing to a 5ghz channel, causes
monitoring to resume.  Bouncing the interface (ip link set mon0
down/up) also fixes it.


Here are some steps to reproduce:

    # setup interface
    iw wlan0 interface add mon0 type monitor
    ip link set mon0 up


    # start channging channels
    while true ; do for i in 1 6 11 ; do iw mon0 set channel $i ; \
    sleep .250 ; done ; done


In a second terminal:
    tcpdump -i mon0


Wait until tcpdump stops printing.  I've seen the failure rate vary
greatly, sometime minutes, sometime hours, but usually less then an
hour.

Regards,

Marco Fonseca