On Thu, Mar 09, 2017 at 02:08:23PM +0100, Thomas Gleixner wrote: > On Wed, 8 Mar 2017, Paul E. McKenney wrote: > > [ 30.694013] lockdep_rcu_suspicious+0xe7/0x120 > > [ 30.694013] get_work_pool+0x82/0x90 > > [ 30.694013] __queue_work+0x70/0x5f0 > > [ 30.694013] queue_work_on+0x33/0x70 > > [ 30.694013] clear_sched_clock_stable+0x33/0x40 > > [ 30.694013] early_init_intel+0xe7/0x2f0 > > [ 30.694013] init_intel+0x11/0x350 > > [ 30.694013] identify_cpu+0x344/0x5a0 > > [ 30.694013] identify_secondary_cpu+0x18/0x80 > > [ 30.694013] smp_store_cpu_info+0x39/0x40 > > [ 30.694013] start_secondary+0x4e/0x100 > > [ 30.694013] start_cpu+0x14/0x14 > > > > Here is the relevant code from x86's smp_callin(): > > > > /* > > * Save our processor parameters. Note: this information > > * is needed for clock calibration. > > */ > > smp_store_cpu_info(cpuid); > > > > The problem is that smp_store_cpu_info() indirectly invokes > > schedule_work(), which wants to use RCU. But RCU isn't informed > > of the incoming CPU until the call to notify_cpu_starting(), which > > causes lockdep to complain bitterly about the use of RCU by the > > premature call to schedule_work(). > > Right. And that want's to be fixed, not hacked around by silencing RCU. > > Peter????
I'm thinking this is hotplug? 30 seconds after boot is far too late for SMP bringup, or you have a stupid slow machine. Because it only calls schedule_work() after SMP-init. In which case there's then two cases, either: - TSC was stable, hotplug wrecked it, TSC is now unstable, and we're screwed. - TSC was unstable, hotplug triggers and we want to mark it unstable _again_. If this is the second, the below should fix it, if its the first, I've no idea yet on how to fix that properly :/ Bloody hotplug.. --- kernel/sched/clock.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sched/clock.c b/kernel/sched/clock.c index a08795e..eecf388 100644 --- a/kernel/sched/clock.c +++ b/kernel/sched/clock.c @@ -172,7 +172,7 @@ void clear_sched_clock_stable(void) smp_mb(); /* matches sched_clock_init_late() */ - if (sched_clock_running == 2) + if (sched_clock_running == 2 && sched_clock_stable()) schedule_work(&sched_clock_work); }