Messages in this thread Patch in this message | | | Date | Fri, 21 Jul 2023 14:43:47 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH] rcu: remove unnecessary check cpu_no_qs.norm on rcu_report_qs_rdp |
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On Fri, Jul 21, 2023 at 01:15:33PM +0100, Levi Yun wrote: > Wherever rcu_report_qs_rdp is called, cpu_no_qs.norm value is false. > Therefore, Remove unnecessary check in rcu_report_qs_rdp. > > Signed-off-by: Levi Yun <ppbuk5246@gmail.com>
Why not start with something like this?
if (!WARN_ON_ONCE(!rdp->cpu_no_qs.b.norm) || rdp->gp_seq != rnp->gp_seq || rdp->gpwrap) {
Except that rcu_report_qs_rdp() is invoked with interrupts enabled, which means that there is some possibility of state changes up to the raw_spin_lock_irqsave_rcu_node(rnp, flags) statement.
So, did you check whether RCU's interrupt paths change this state?
Thanx, Paul
> --- > kernel/rcu/tree.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index 1449cb69a0e0..d840596e9903 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -1962,8 +1962,7 @@ rcu_report_qs_rdp(struct rcu_data *rdp) > WARN_ON_ONCE(rdp->cpu != smp_processor_id()); > rnp = rdp->mynode; > raw_spin_lock_irqsave_rcu_node(rnp, flags); > - if (rdp->cpu_no_qs.b.norm || rdp->gp_seq != rnp->gp_seq || > - rdp->gpwrap) { > + if (rdp->gp_seq != rnp->gp_seq || rdp->gpwrap) { > > /* > * The grace period in which this quiescent state was > -- > 2.37.2
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