On Wed, 2 Oct 2019 18:33:01 -0700 [email protected] wrote: > From: "Joel Fernandes (Google)" <[email protected]> > > The RCU-specific resched_cpu() function sends a resched IPI to the > specified CPU, which can be used to force the tick on for a given > nohz_full CPU. This is needed when this nohz_full CPU is looping in the > kernel while blocking the current grace period. However, for the tick > to actually be forced on in all cases, that CPU's rcu_data structure's > ->rcu_urgent_qs flag must be set beforehand. This commit therefore > causes rcu_implicit_dynticks_qs() to set this flag prior to invoking > resched_cpu() on a holdout nohz_full CPU.
Should this be marked for stable? -- Steve > > Signed-off-by: Joel Fernandes (Google) <[email protected]> > Signed-off-by: Paul E. McKenney <[email protected]> > --- > kernel/rcu/tree.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index 8110514..0d83b19 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -1073,6 +1073,7 @@ static int rcu_implicit_dynticks_qs(struct rcu_data > *rdp) > if (tick_nohz_full_cpu(rdp->cpu) && > time_after(jiffies, > READ_ONCE(rdp->last_fqs_resched) + jtsq * 3)) { > + WRITE_ONCE(*ruqp, true); > resched_cpu(rdp->cpu); > WRITE_ONCE(rdp->last_fqs_resched, jiffies); > }
