linux-kernel - Re: [PATCH 1/4] rcu: Speed up calling of RCU tasks callbacks

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Date:   Thu, 24 May 2018 18:42:08 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:     Joel Fernandes <joelaf@...gle.com>, linux-kernel@...r.kernel.org,
        "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        Peter Zilstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Boqun Feng <boqun.feng@...il.com>, byungchul.park@....com,
        kernel-team@...roid.com, Josh Triplett <josh@...htriplett.org>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: [PATCH 1/4] rcu: Speed up calling of RCU tasks callbacks

On Thu, 24 May 2018 15:38:39 -0700
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> wrote:

> On Thu, May 24, 2018 at 05:47:52PM -0400, Steven Rostedt wrote:
> > On Wed, 23 May 2018 13:04:58 -0700
> > "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> wrote:
> >   
> > > Looks plausible to me!
> > >   
> > 
> > BTW looking at the code:
> >   
> > > 		/* Invoke the callbacks. */
> > > 		while (list) {
> > > 			next = list->next;
> > > 			local_bh_disable();
> > > 			list->func(list);
> > > 			local_bh_enable();
> > > 			list = next;
> > > 			cond_resched();
> > > 		}
> > > 		schedule_timeout_uninterruptible(HZ/10);  
> > 
> > What's the purpose of this final sleep?  
> 
> To avoid any possibility of rcu_tasks_kthread() getting into a tight loop.
> 

OK, so I'll send out a v4 of what I just sent out ;-)

-- Steve