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

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Message-Id: <20180524223839.GU3803@linux.vnet.ibm.com>
Date:   Thu, 24 May 2018 15:38:39 -0700
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     Steven Rostedt <rostedt@...dmis.org>
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, 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.

							Thanx, Paul