Messages in this thread | | | Date | Thu, 29 Oct 2020 09:06:33 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [RFC][PATCH v3 6/6] rcu/tree: Use irq_work_queue_remote() |
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On Thu, Oct 29, 2020 at 10:15:34AM +0100, Peter Zijlstra wrote: > On Wed, Oct 28, 2020 at 01:15:54PM -0700, Paul E. McKenney wrote: > > On Wed, Oct 28, 2020 at 09:02:43PM +0100, Peter Zijlstra wrote: > > > -#ifdef CONFIG_IRQ_WORK > > > + raw_spin_lock_rcu_node(rnp); > > > > The caller of rcu_implicit_dynticks_qs() already holds this lock. > > Please see the force_qs_rnp() function and its second call site, > > to which rcu_implicit_dynticks_qs() is passed as an argument. > > Like this then.
This does look plausible! But I am sure that rcutorture will also have an opinion. ;-)
Thanx, Paul
> --- > Subject: rcu/tree: Use irq_work_queue_remote() > From: Peter Zijlstra <peterz@infradead.org> > Date: Wed Oct 28 11:53:40 CET 2020 > > The effect of an self-IPI here would be setting rcu_iw_gp_seq to the > value we just set it to (pointless) and clearing rcu_iw_pending, which > we just set, so don't set it. > > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > --- > kernel/rcu/tree.c | 10 ++++++---- > 1 file changed, 6 insertions(+), 4 deletions(-) > > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -1204,6 +1204,8 @@ static int rcu_implicit_dynticks_qs(stru > bool *ruqp; > struct rcu_node *rnp = rdp->mynode; > > + raw_lockdep_assert_held_rcu_node(rnp); > + > /* > * If the CPU passed through or entered a dynticks idle phase with > * no active irq/NMI handlers, then we can safely pretend that the CPU > @@ -1308,14 +1310,14 @@ static int rcu_implicit_dynticks_qs(stru > resched_cpu(rdp->cpu); > WRITE_ONCE(rdp->last_fqs_resched, jiffies); > } > -#ifdef CONFIG_IRQ_WORK > if (!rdp->rcu_iw_pending && rdp->rcu_iw_gp_seq != rnp->gp_seq && > (rnp->ffmask & rdp->grpmask)) { > - rdp->rcu_iw_pending = true; > rdp->rcu_iw_gp_seq = rnp->gp_seq; > - irq_work_queue_on(&rdp->rcu_iw, rdp->cpu); > + if (likely(rdp->cpu != smp_processor_id())) { > + rdp->rcu_iw_pending = true; > + irq_work_queue_remote(rdp->cpu, &rdp->rcu_iw); > + } > } > -#endif > } > > return 0;
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