Re: [PATCH] rcu: Fix up pending cbs check in rcu_prepare_for_idle

[Neeraj Upadhyay]

On 08/07/2017 06:10 PM, Paul E. McKenney wrote:
> On Mon, Aug 07, 2017 at 11:20:10AM +0530, Neeraj Upadhyay wrote:
> > Pending cbs check in rcu_prepare_for_idle is inversed
> > in the sense that, it should accelerate if there are
> > pending cbs; but, the check does the opposite. So,
> > fix it.
> >
> > Fixes: 15fecf89e46a ("srcu: Abstract multi-tail callback list handling")
> > Signed-off-by: Neeraj Upadhyay <neeraju@xxxxxxxxxxxxxx>
> Good catch!  Queued for review and testing.
>
> Just out of curiosity, how did you find this one?
>
> 							Thanx, Paul

Hi Paul, found the issue while reading the code.

> > ---
> >   kernel/rcu/tree_plugin.h | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
> > index 908b309..b8f51df 100644
> > --- a/kernel/rcu/tree_plugin.h
> > +++ b/kernel/rcu/tree_plugin.h
> > @@ -1493,7 +1493,7 @@ static void rcu_prepare_for_idle(void)
> >   	rdtp->last_accelerate = jiffies;
> >   	for_each_rcu_flavor(rsp) {
> >   		rdp = this_cpu_ptr(rsp->rda);
> > -		if (rcu_segcblist_pend_cbs(&rdp->cblist))
> > +		if (!rcu_segcblist_pend_cbs(&rdp->cblist))
> >   			continue;
> >   		rnp = rdp->mynode;
> >   		raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */
> > --
> > QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
> > member of the Code Aurora Forum, hosted by The Linux Foundation

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QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
member of the Code Aurora Forum, hosted by The Linux Foundation