Subject: suspicious RCU usage clockevents_lock, tick_broadcast_lock, hrtimer_bases.lock

From: Sam Bobroff <[email-masked]>
Date: Fri, 13 Feb 2015 11:57:26 +1100

Hello,

I'm receiving this while booting a vanilla 3.19 kernel on a Power 8 machine:

[    2.522179] device-mapper: uevent: version 1.0.3
[    2.522741] device-mapper: ioctl: 4.29.0-ioctl (2014-10-28)
initialised: [email-masked]
[    2.543590]
[    2.543630] ===============================
[    2.543709] [ INFO: suspicious RCU usage. ]
[    2.543758] 3.19.0samb #2 Not tainted
[    2.543802] -------------------------------
[    2.543847] include/trace/events/timer.h:186 suspicious
rcu_dereference_check() usage!
[    2.543940]
[    2.543940] other info that might help us debug this:
[    2.543940]
[    2.544035]
[    2.544035] RCU used illegally from idle CPU!
[    2.544035] rcu_scheduler_active = 1, debug_locks = 0
[    2.544154] RCU used illegally from extended quiescent state!
[    2.544234] 3 locks held by swapper/1/0:
[    2.544284]  #0:  (clockevents_lock){-.....}, at:
[<c0000000001a45cc>] .clockevents_notify+0x5c/0x320
[    2.544464]  #1:  (tick_broadcast_lock){-.-...}, at:
[<c0000000001a7ac4>] .tick_broadcast_oneshot_control+0xe4/0x530
[    2.544654]  #2:  (hrtimer_bases.lock#2){-.-...}, at:
[<c000000000192694>] .__hrtimer_start_range_ns+0x124/0x6e0
[    2.544843]
[    2.544843] stack backtrace:
[    2.544904] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 3.19.0samb #2
[    2.544986] Call Trace:
[    2.545023] [c000000fdf6f7770] [c000000000faf118]
.dump_stack+0x98/0xd4 (unreliable)
[    2.545124] [c000000fdf6f77f0] [c000000000152b78]
.lockdep_rcu_suspicious+0x138/0x180
[    2.545225] [c000000fdf6f7880] [c000000000191374]
.enqueue_hrtimer+0x1c4/0x300
[    2.545325] [c000000fdf6f7910] [c00000000019276c]
.__hrtimer_start_range_ns+0x1fc/0x6e0
[    2.545425] [c000000fdf6f7a10] [c0000000001a8e90] .bc_set_next+0xc0/0xf0
[    2.545510] [c000000fdf6f7aa0] [c0000000001a51f0]
.clockevents_program_event+0x100/0x1f0
[    2.545607] [c000000fdf6f7b40] [c0000000001a6bac]
.tick_broadcast_set_event+0x6c/0x120
[    2.545705] [c000000fdf6f7bd0] [c0000000001a7c94]
.tick_broadcast_oneshot_control+0x2b4/0x530
[    2.545802] [c000000fdf6f7ca0] [c0000000001a4818]
.clockevents_notify+0x2a8/0x320
[    2.545898] [c000000fdf6f7d70] [c0000000001484f4]
.cpu_startup_entry+0x404/0x730
[    2.545995] [c000000fdf6f7ec0] [c000000000044314]
.start_secondary+0x3a4/0x460
[    2.546092] [c000000fdf6f7f90] [c000000000008bfc]
start_secondary_prolog+0x10/0x14
[    2.546555] Registering IBM Power 842 compression driver

Cheers,
Sam.