linux-kernel - Re: [PATCH 08/10] rcu: Allow to deactivate nocb on a CPU

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Message-ID: <20200604131409.GB27571@lenoir>
Date:   Thu, 4 Jun 2020 15:14:09 +0200
From:   Frederic Weisbecker <frederic@...nel.org>
To:     Joel Fernandes <joel@...lfernandes.org>
Cc:     "Paul E . McKenney" <paulmck@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Josh Triplett <josh@...htriplett.org>
Subject: Re: [PATCH 08/10] rcu: Allow to deactivate nocb on a CPU

On Tue, May 26, 2020 at 05:20:17PM -0400, Joel Fernandes wrote:
> On Wed, May 13, 2020 at 06:47:12PM +0200, Frederic Weisbecker wrote:
> > Allow a CPU's rdp to quit the callback offlined mode.
> 
> nit: s/offlined/offloaded/ ?

Oh, looks like I did that everywhere :)

> 
> > The switch happens on the target with IRQs disabled and rdp->nocb_lock
> > held to avoid races between local callbacks handling and kthread
> > offloaded callbacks handling.
> > nocb_cb kthread is first parked to avoid any future race with
> > concurrent rcu_do_batch() executions. Then the cblist is set to offloaded
> > so that the nocb_gp kthread ignores this rdp.
> 
> nit: you mean cblist is set to non-offloaded mode right?

Ah right!

> > +static void __rcu_nocb_rdp_deoffload(struct rcu_data *rdp)
> > +{
> > +	unsigned long flags;
> > +	struct rcu_node *rnp = rdp->mynode;
> > +
> > +	printk("De-offloading %d\n", rdp->cpu);
> 
> nit: s/printk/pr_debug/ ?

Ok.

Thanks!