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Message-ID: <20161122081220.GG2279@X58A-UD3R>
Date: Tue, 22 Nov 2016 17:12:20 +0900
From: Byungchul Park <byungchul.park@....com>
To: paulmck@...ux.vnet.ibm.com, josh@...htriplett.org,
rostedt@...dmis.org, mathieu.desnoyers@...icios.com,
jiangshanlai@...il.com
Cc: linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] rcu: Force resched_cpu when jiffies >=
rcu_state.jiffies_resched
On Wed, Nov 09, 2016 at 03:32:15PM +0900, Byungchul Park wrote:
> Currently rcu code forces CPU into scheduler when jiffies >=
> rcu_state.gp_start + jiffies_till_sched_qs, via resched_cpu().
>
> It would be better to force CPU into scheduler when jiffies >=
> rcu_state.jiffies_resched, too.
Hello,
I think these two patches are necessary to call resched_cpu() even in
case of jiffies >= rcu_state.jiffies_resched, too. Am I wrong?
It would be appriciated if you let me know if I was wrong.
Thank you,
Byungchul
>
> Signed-off-by: Byungchul Park <byungchul.park@....com>
> ---
> kernel/rcu/tree.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index d8e8859..287f468 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -1217,11 +1217,10 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp,
> READ_ONCE(*rcrmp) + rdp->rsp->flavor_mask);
> }
> 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 + jiffies_till_sched_qs))
> + /* And if it has been a really long time, kick the CPU as well. */
> resched_cpu(rdp->cpu); /* Force CPU into scheduler. */
> + }
>
> return 0;
> }
> --
> 1.9.1
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