From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Byungchul Park <byungchul.park@lge.com>
Cc: josh@joshtriplett.org, rostedt@goodmis.org,
mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] rcu: Force resched_cpu when jiffies >= rcu_state.jiffies_resched
Date: Fri, 25 Nov 2016 00:34:26 -0800 [thread overview]
Message-ID: <20161125083426.GC31360@linux.vnet.ibm.com> (raw)
In-Reply-To: <20161122081220.GG2279@X58A-UD3R>
On Tue, Nov 22, 2016 at 05:12:20PM +0900, Byungchul Park wrote:
> 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.
My current thought is that both the "if" statement and the call to
resched_cpu() should be removed, but I am still testing and working
through the timing.
Either way, I do very much appreciate your having called my attention
to this code!
Thanx, Paul
> Thank you,
> Byungchul
>
> >
> > Signed-off-by: Byungchul Park <byungchul.park@lge.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
>
next prev parent reply other threads:[~2016-11-25 8:37 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-09 6:32 [PATCH 1/2] rcu: Remove unnecessary condition in rcu_implicit_dynticks_qs Byungchul Park
2016-11-09 6:32 ` [PATCH 2/2] rcu: Force resched_cpu when jiffies >= rcu_state.jiffies_resched Byungchul Park
2016-11-22 8:12 ` Byungchul Park
2016-11-25 8:34 ` Paul E. McKenney [this message]
2016-11-26 12:00 ` Paul E. McKenney
2016-11-28 6:46 ` Byungchul Park
2016-11-28 10:58 ` Paul E. McKenney
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20161125083426.GC31360@linux.vnet.ibm.com \
--to=paulmck@linux.vnet.ibm.com \
--cc=byungchul.park@lge.com \
--cc=jiangshanlai@gmail.com \
--cc=josh@joshtriplett.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mathieu.desnoyers@efficios.com \
--cc=rostedt@goodmis.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).