bcmwl crashes kernel when monitor mode enabled

[Brian Candler]

Ubuntu 14.04 with linux-generic-lts-xenial kernel (4.4.0), running on Macmini6,2

Installed package bcmwl-kernel-source, which gives me this module for my wlan0:

# lsmod | grep wl
wl 6365184 0
cfg80211 557056 1 wl

Machine immediately and reliably crashes when I do the following:

# echo 1 > /proc/brcm_monitor0

At that time, console displays the following (hand-transcribed from slightly fuzzy photo):

[ 313.202989] xhci_hcd 0000:00:14.0: HC died; cleaning up
[ 313.203118] asix 3-4:1.0 eth1: Failed to enable software MII access
[ 313.203148] asix 3-4:1.0 eth1: Failed to enable software MII access
[ 313.203174] asix 3-4:1.0 eth1: Failed to enable software MII access
[ 313.203200] asix 3-4:1.0 eth1: Failed to enable software MII access
[ 313.908406] NMI watchdog: Watchdog detected hard LOCKUP on cpu 0
[ 328.127778] NMI watchdog: BUG: soft lockup - CPU#6 stuck for 22s! [charts.d.plugin:12702]
[ 356.129362] NMI watchdog: BUG: soft lockup - CPU#6 stuck for 22s! [charts.d.plugin:12702]
[ 361.369660] INFO: rcu_sched detected stalls on CPUs/tasks:
[ 361.369691] N0-..: (1 GPs behind) idle=8fd/140000000000000/0 softirq=18394/18394 fqs=14978
[ 361.369717] N(detected by 3, t=15002 jiffies, g=10311, c=10310, q=74589)
[ 384.130946] NMI watchdog: BUG: soft lockup - CPU#6 stuck for 22s! [charts.d.plugin:12702]

Note: "charts.d.plugin" I believe refers to the 'netdata' application which I also have running. However as it's just a userland process I don't think it should be able to kill the kernel like this.

Workaround: I was installing this to try to get monitor mode working. However I will revert to b43 driver (which unfortunately does not appear to do promiscuous monitor mode)

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: bcmwl-kernel-source 6.30.223.248+bdcom-0ubuntu0.2
ProcVersionSignature: Ubuntu 4.4.0-28.47~14.04.1-generic 4.4.13
Uname: Linux 4.4.0-28-generic x86_64
NonfreeKernelModules: wl
ApportVersion: 2.14.1-0ubuntu3.21
Architecture: amd64
Date: Mon Jul 25 18:14:03 2016
InstallationDate: Installed on 2014-07-16 (740 days ago)
InstallationMedia: Ubuntu-Server 14.04 LTS "Trusty Tahr" - Release amd64 (20140416.2)
ProcEnviron:
 SHELL=/bin/bash
 TERM=xterm-256color
 PATH=(custom, no user)
 LANG=en_GB.UTF-8
 LANGUAGE=en_GB:en
SourcePackage: bcmwl
UpgradeStatus: No upgrade log present (probably fresh install)