From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>,
hpa@zytor.com, linux-kernel@vger.kernel.org,
rakib.mullick@gmail.com, tglx@linutronix.de,
linux-tip-commits@vger.kernel.org
Subject: Re: [tip:sched/core] sched: Fix load avg vs cpu-hotplug
Date: Wed, 5 Sep 2012 16:39:51 -0700 [thread overview]
Message-ID: <20120905233951.GX3308@linux.vnet.ibm.com> (raw)
In-Reply-To: <1346882630.2600.59.camel@twins>
On Thu, Sep 06, 2012 at 12:03:50AM +0200, Peter Zijlstra wrote:
> On Wed, 2012-09-05 at 19:01 +0200, Peter Zijlstra wrote:
> > > Please do a delta.
>
> OK, so I suppose something like the below ought to do. Paul its slightly
> different than the one in your tree, given the changelog below, do you
> see anything wrong with it?
>
> Rakib, again, sorry for getting your name wrong, and this time for
> getting it merged :/
>
> ---
> Subject: sched: Fix load avg vs cpu-hotplug mk-II
>
> Commit f319da0c68 ("sched: Fix load avg vs cpu-hotplug") was a known
> broken version that got in by accident.
>
> In particular, the problem is that at the point it calls
> calc_load_migrate() nr_running := 1 (the stopper thread), so move the
> call to CPU_DEAD where we're sure that nr_running := 0.
>
> Also note that we can call calc_load_migrate() without serialization, we
> know the state of rq is stable since its cpu is dead, and we modify the
> global state using appropriate atomic ops.
>
> Suggested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Given your point about atomic ops, my version was indeed overkill.
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> ---
> kernel/sched/core.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index c46a011..8c089cb 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -5086,7 +5086,9 @@ migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu)
> migrate_tasks(cpu);
> BUG_ON(rq->nr_running != 1); /* the migration thread */
> raw_spin_unlock_irqrestore(&rq->lock, flags);
> + break;
>
> + case CPU_DEAD:
> calc_load_migrate(rq);
> break;
> #endif
>
next prev parent reply other threads:[~2012-09-05 23:39 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-16 13:45 Add rq->nr_uninterruptible count to dest cpu's rq while CPU goes down Rakib Mullick
2012-08-16 13:56 ` Peter Zijlstra
2012-08-16 14:28 ` Rakib Mullick
2012-08-16 14:42 ` Peter Zijlstra
2012-08-16 15:32 ` Rakib Mullick
2012-08-16 17:46 ` Peter Zijlstra
2012-08-17 13:39 ` Rakib Mullick
2012-08-20 9:26 ` Peter Zijlstra
2012-08-20 16:10 ` Rakib Mullick
2012-08-20 16:16 ` Peter Zijlstra
2012-08-20 16:26 ` Paul E. McKenney
2012-08-27 18:44 ` Paul E. McKenney
2012-08-28 6:57 ` Rakib Mullick
2012-08-28 13:42 ` Paul E. McKenney
2012-08-28 16:52 ` Rakib Mullick
2012-08-28 17:07 ` Paul E. McKenney
2012-08-29 1:05 ` Rakib Mullick
2012-09-04 18:43 ` [tip:sched/core] sched: Fix load avg vs cpu-hotplug tip-bot for Peter Zijlstra
2012-09-05 12:36 ` Peter Zijlstra
2012-09-05 13:29 ` Ingo Molnar
2012-09-05 17:01 ` Peter Zijlstra
2012-09-05 17:34 ` Ingo Molnar
2012-09-05 22:03 ` Peter Zijlstra
2012-09-05 23:39 ` Paul E. McKenney [this message]
2012-09-06 3:30 ` Rakib Mullick
2012-09-14 6:14 ` [tip:sched/core] sched: Fix load avg vs. cpu-hotplug tip-bot for Peter Zijlstra
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=20120905233951.GX3308@linux.vnet.ibm.com \
--to=paulmck@linux.vnet.ibm.com \
--cc=hpa@zytor.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-tip-commits@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=peterz@infradead.org \
--cc=rakib.mullick@gmail.com \
--cc=tglx@linutronix.de \
/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).