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Date:   Thu, 24 May 2018 15:38:39 -0700
From:   "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To:     Steven Rostedt <rostedt@goodmis.org>
Cc:     Joel Fernandes <joelaf@google.com>, linux-kernel@vger.kernel.org,
        "Joel Fernandes (Google)" <joel@joelfernandes.org>,
        Peter Zilstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Boqun Feng <boqun.feng@gmail.com>, byungchul.park@lge.com,
        kernel-team@android.com, Josh Triplett <josh@joshtriplett.org>,
        Lai Jiangshan <jiangshanlai@gmail.com>,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Subject: Re: [PATCH 1/4] rcu: Speed up calling of RCU tasks callbacks
Reply-To: paulmck@linux.vnet.ibm.com
References: <20180523063815.198302-1-joel@joelfernandes.org>
 <20180523063815.198302-2-joel@joelfernandes.org>
 <20180523155734.GK3803@linux.vnet.ibm.com>
 <20180523124531.7b0e972a@gandalf.local.home>
 <20180523170303.GR3803@linux.vnet.ibm.com>
 <20180523151337.469bba34@gandalf.local.home>
 <20180523200458.GD3803@linux.vnet.ibm.com>
 <20180524174752.0928d562@gandalf.local.home>
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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@linux.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