On Thu, 2018-05-03 at 18:45 +0200, Peter Zijlstra wrote: > > Something like so perhaps? Mike, can you play around with that? Could > burn your granny and eat your cookies.
That worked, and nothing entertaining has happened.. yet. Hm, I could use this kernel to update my backup drive, if there's a cookie monster lurking, that might get its attention :) > diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c > index 7468de429087..07360523c3ce 100644 > --- a/arch/x86/kernel/cpu/mtrr/main.c > +++ b/arch/x86/kernel/cpu/mtrr/main.c > @@ -793,6 +793,9 @@ void mtrr_ap_init(void) > > if (!use_intel() || mtrr_aps_delayed_init) > return; > + > + rcu_cpu_starting(smp_processor_id()); > + > /* > * Ideally we should hold mtrr_mutex here to avoid mtrr entries > * changed, but this routine will be called in cpu boot time, > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index 2a734692a581..4dab46950fdb 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -3775,6 +3775,8 @@ int rcutree_dead_cpu(unsigned int cpu) > return 0; > } > > +static DEFINE_PER_CPU(int, rcu_cpu_started); > + > /* > * Mark the specified CPU as being online so that subsequent grace periods > * (both expedited and normal) will wait on it. Note that this means that > @@ -3796,6 +3798,11 @@ void rcu_cpu_starting(unsigned int cpu) > struct rcu_node *rnp; > struct rcu_state *rsp; > > + if (per_cpu(rcu_cpu_started, cpu)) > + return; > + > + per_cpu(rcu_cpu_started, cpu) = 1; > + > for_each_rcu_flavor(rsp) { > rdp = per_cpu_ptr(rsp->rda, cpu); > rnp = rdp->mynode; > @@ -3852,6 +3859,8 @@ void rcu_report_dead(unsigned int cpu) > preempt_enable(); > for_each_rcu_flavor(rsp) > rcu_cleanup_dying_idle_cpu(cpu, rsp); > + > + per_cpu(rcu_cpu_started, cpu) = 0; > } > > /* Migrate the dead CPU's callbacks to the current CPU. */