On Thu, May 03, 2018 at 03:32:39PM +0200, Mike Galbraith wrote: > Dang. With $subject fix applied as well..
That's a NO then... :-( > [ 151.103732] smpboot: Booting Node 0 Processor 2 APIC 0x4 > [ 151.104908] ============================= > [ 151.104909] WARNING: suspicious RCU usage > [ 151.104910] 4.17.0.g66d489e-tip-default #84 Tainted: G E > [ 151.104911] ----------------------------- > [ 151.104912] kernel/sched/core.c:1625 suspicious rcu_dereference_check() > usage! > [ 151.104913] > other info that might help us debug this: > > [ 151.104914] > RCU used illegally from offline CPU! > rcu_scheduler_active = 2, debug_locks = 0 > [ 151.104916] 3 locks held by swapper/2/0: > [ 151.104916] #0: 00000000560adb60 (stop_cpus_mutex){+.+.}, at: > stop_machine_from_inactive_cpu+0x86/0x140 > [ 151.104923] #1: 00000000e4fb0238 (&p->pi_lock){-.-.}, at: > try_to_wake_up+0x2d/0x5f0 > [ 151.104929] #2: 000000003341403b (rcu_read_lock){....}, at: > rcu_read_lock+0x0/0x80 > [ 151.104934] > stack backtrace: > [ 151.104937] CPU: 2 PID: 0 Comm: swapper/2 Kdump: loaded Tainted: G > E 4.17.0.g66d489e-tip-default #84 > [ 151.104938] Hardware name: MEDION MS-7848/MS-7848, BIOS M7848W08.20C > 09/23/2013 > [ 151.104938] Call Trace: > [ 151.104942] dump_stack+0x78/0xb3 > [ 151.104945] ttwu_stat+0x121/0x130 > [ 151.104949] try_to_wake_up+0x2c2/0x5f0 > [ 151.104953] ? cpu_stop_park+0x30/0x30 > [ 151.104956] wake_up_q+0x4a/0x70 > [ 151.104959] cpu_stop_queue_work+0x6b/0xa0 > [ 151.104963] queue_stop_cpus_work+0x61/0xb0 > [ 151.104968] stop_machine_from_inactive_cpu+0xd8/0x140 > > diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c > > index f89014a2c238..a32518c2ba4a 100644 > > --- a/kernel/stop_machine.c > > +++ b/kernel/stop_machine.c > > @@ -650,8 +650,10 @@ int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, > > void *data, > > /* Schedule work on other CPUs and execute directly for local CPU */ > > set_state(&msdata, MULTI_STOP_PREPARE); > > cpu_stop_init_done(&done, num_active_cpus()); > > - queue_stop_cpus_work(cpu_active_mask, multi_cpu_stop, &msdata, > > - &done); > > + > > + RCU_NONIDLE(queue_stop_cpus_work(cpu_active_mask, multi_cpu_stop, > > + &msdata, &done)); > > + > > ret = multi_cpu_stop(&msdata); Paul, any clue on what else to try here? The whole MTRR setup is radically crazy but it's something we're stuck with (yay hardware) :/ So the issue is that we're doing wakeups from an offline CPU (very early during bringup) and RCU (rightfully) complains about that. I thought RCU_NONIDLE() was the magic incantation that makes RCU 'watch', but clearly it's not enough here.