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

Josh Triplett
2017-01-21T20:44:05Z

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?

> 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
>