From: Frederic Weisbecker <fweisbec@gmail.com>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Josh Triplett <josh@joshtriplett.org>,
LKML <linux-kernel@vger.kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Subject: Re: [PATCH] rcu: Only pin GP kthread when full dynticks is actually used
Date: Sat, 14 Jun 2014 15:05:50 +0200 [thread overview]
Message-ID: <20140614130548.GC16504@localhost.localdomain> (raw)
In-Reply-To: <20140614050606.GD4581@linux.vnet.ibm.com>
On Fri, Jun 13, 2014 at 10:06:06PM -0700, Paul E. McKenney wrote:
> One complication... So if the grace period has gone on for a long time,
> and you are returning to kernel mode, RCU will need the scheduling-clock
> tick. However, in that very same situation, if you are returning to
> idle or to NO_HZ_FULL userspace execution, RCU does -not- need the
> scheduling-clock tick set.
Right.
> One way I could do this is to have rcu_needs_cpu() return three values:
> Zero for RCU doesn't need a scheduling-clock tick for any reason,
> one if RCU needs a scheduling-clock tick only if returning to kernel
> mode, and two if RCU unconditionally needs the scheduling-clock tick.
> Would that work, or is there a better approach?
For an interrupt, based on the context tracking state, I can check where we
return afterward if we are in an interrupt using context_tracking_in_user().
Now probably rcu_needs_cpu() should check that by itself and, depending
on where we return, only tell if we keep the tick or not.
What do you think?
next prev parent reply other threads:[~2014-06-14 13:05 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-13 0:16 [PATCH] rcu: Only pin GP kthread when full dynticks is actually used Frederic Weisbecker
2014-06-13 1:24 ` Paul E. McKenney
2014-06-13 1:35 ` Paul E. McKenney
2014-06-13 12:47 ` Frederic Weisbecker
2014-06-13 15:52 ` Paul E. McKenney
2014-06-13 16:00 ` Frederic Weisbecker
2014-06-13 16:16 ` Paul E. McKenney
2014-06-13 16:21 ` Frederic Weisbecker
2014-06-13 16:44 ` Josh Triplett
2014-06-13 20:48 ` Paul E. McKenney
2014-06-13 21:10 ` Josh Triplett
2014-06-13 22:49 ` Paul E. McKenney
2014-06-13 23:10 ` Frederic Weisbecker
2014-06-13 23:27 ` Paul E. McKenney
2014-06-13 23:39 ` Frederic Weisbecker
2014-06-14 5:06 ` Paul E. McKenney
2014-06-14 11:26 ` Paul E. McKenney
2014-06-14 13:10 ` Frederic Weisbecker
2014-06-14 14:29 ` Paul E. McKenney
2014-06-14 13:05 ` Frederic Weisbecker [this message]
2014-06-13 20:49 ` Paul E. McKenney
2014-06-13 23:13 ` Frederic Weisbecker
2014-06-13 23:22 ` Paul E. McKenney
2014-06-13 2:05 ` Paul E. McKenney
2014-06-13 12:55 ` Frederic Weisbecker
2014-06-13 15:55 ` Paul E. McKenney
2014-06-13 16:03 ` Frederic Weisbecker
2014-06-13 16:20 ` Paul E. McKenney
2014-06-13 16:10 ` Paul E. McKenney
2014-06-13 12:42 ` Frederic Weisbecker
2014-06-13 15:58 ` Paul E. McKenney
2014-06-13 16:09 ` Frederic Weisbecker
2014-06-13 16:23 ` Paul E. McKenney
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