Re: [PATCH v2 tip/core/rcu 08/18] rcu: Remove short-term CPU kicking

Paul E. McKenney
2017-01-23T19:36:40Z

On Sat, Jan 21, 2017 at 12:43:44PM -0800, Josh Triplett wrote:
> On Tue, Jan 17, 2017 at 06:53:47PM -0800, Paul E. McKenney wrote:
> > Commit 4914950aaa12d ("rcu: Stop treating in-kernel CPU-bound workloads
>
> Does this commit ID still match what you have in your tree, post-rebase?

In light of your earlier email, good question! But this one is still
OK because it is already in mainline.

Thanx, Paul

> > as errors") added a (relatively) short-timeout call to resched_cpu().
> > This was inspired by as issue that was fixed by b7e7ade34e61 ("sched/core:
> > Fix remote wakeups"). But given that this issue was fixed, it is time
> > for the current commit to remove this call to resched_cpu().
> >
> > Reported-by: Byungchul Park <byungchul.park@lge.com>
> > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> > Reviewed-by: Josh Triplett <josh@joshtriplett.org>
> > ---
> > kernel/rcu/tree.c | 5 -----
> > 1 file changed, 5 deletions(-)
> >
> > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> > index 0e61b62e3f4a..5a4aaad75e76 100644
> > --- a/kernel/rcu/tree.c
> > +++ b/kernel/rcu/tree.c
> > @@ -1220,11 +1220,6 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp,
> > rdp->rsp->jiffies_resched += 5; /* Re-enable beating. */
> > }
> >
> > - /* And if it has been a really long time, kick the CPU as well. */
> > - if (ULONG_CMP_GE(jiffies,
> > - rdp->rsp->gp_start + 2 * jiffies_till_sched_qs) ||
> > - ULONG_CMP_GE(jiffies, rdp->rsp->gp_start + jiffies_till_sched_qs))
> > - resched_cpu(rdp->cpu); /* Force CPU into scheduler. */
> > /*
> > * If more than halfway to RCU CPU stall-warning time, do
> > * a resched_cpu() to try to loosen things up a bit.
> > --
> > 2.5.2
> >
>