v4.15-rc7 regression/warning: suspicious RCU usage in net/wireless/util.c:778

[Dominik Brodowski <linux@dominikbrodowski.net>]

On Sat, Dec 30, 2017 at 02:11:33PM +0100, Dominik Brodowski wrote:
> On Fri, Dec 22, 2017 at 08:20:12AM +0100, Dominik Brodowski wrote:
> > Dear all,
> > 
> > once the (wifi) link becomes ready, the following warning is emitted on
> > mainline (v4.15-rc4-202-gead68f216110) on my notebook:
> 
> ... and it is still present as of v4.15-rc5-149-g5aa90a845892

... and still present in v4.15-rc7:

[    0.000000] Linux version 4.15.0-rc7+ (brodo@light) (gcc version 7.2.1 20171224 (GCC)) #2 SMP PREEMPT Mon Jan 8 08:58:57 CET 2018
...
[   19.182497] wlan0: associated
[   19.323473] IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready

[   19.324512] =============================
[   19.324525] WARNING: suspicious RCU usage
[   19.324531] 4.15.0-rc7+ #2 Not tainted
[   19.324535] -----------------------------
[   19.324541] /home/brodo/local/kernel/git/linux/net/wireless/util.c:778 suspicious rcu_dereference_check() usage!
[   19.324545] 
               other info that might help us debug this:

[   19.324551] 
               rcu_scheduler_active = 2, debug_locks = 1
[   19.324556] 4 locks held by wpa_supplicant/777:
[   19.324561]  #0:  (cb_lock){++++}, at: [<00000000a93b95ca>] genl_rcv+0x15/0x40
[   19.324590]  #1:  (genl_mutex){+.+.}, at: [<0000000088de9868>] genl_rcv_msg+0x7a/0x90
[   19.324614]  #2:  (rtnl_mutex){+.+.}, at: [<00000000d05b811d>] nl80211_pre_doit+0xe9/0x190
[   19.324639]  #3:  (&wdev->mtx){+.+.}, at: [<0000000015e6766b>] nl80211_send_iface+0x319/0x8d0
[   19.324663] 
               stack backtrace:
[   19.324670] CPU: 3 PID: 777 Comm: wpa_supplicant Not tainted 4.15.0-rc7+ #2
[   19.324674] Hardware name: Dell Inc. XPS 13 9343/0TM99H, BIOS A11 12/08/2016
[   19.324679] Call Trace:
[   19.324690]  dump_stack+0x67/0x95
[   19.324698]  ieee80211_bss_get_ie+0x66/0x70
[   19.324707]  nl80211_send_iface+0x346/0x8d0
[   19.324726]  nl80211_get_interface+0x4b/0xa0
[   19.324738]  genl_family_rcv_msg+0x32e/0x3f0
[   19.324747]  ? preempt_count_sub+0x92/0xd0
[   19.324780]  genl_rcv_msg+0x47/0x90
[   19.324787]  ? genl_family_rcv_msg+0x3f0/0x3f0
[   19.324796]  netlink_rcv_skb+0x8a/0x120
[   19.324811]  genl_rcv+0x24/0x40
[   19.324818]  netlink_unicast+0x174/0x1f0
[   19.324831]  netlink_sendmsg+0x383/0x3d0
[   19.324851]  sock_sendmsg+0x2d/0x40
[   19.324859]  ___sys_sendmsg+0x2a8/0x300
[   19.324877]  ? netlink_sendmsg+0x13a/0x3d0
[   19.324919]  ? __sys_sendmsg+0x67/0xb0
[   19.324925]  __sys_sendmsg+0x67/0xb0
[   19.324949]  entry_SYSCALL_64_fastpath+0x18/0x85
[   19.324955] RIP: 0033:0x779ea30ac037
[   19.324960] RSP: 002b:00007ffd9ea8aa28 EFLAGS: 00000246

Anyone?

Thanks,
	Dominik