linux-kernel - Re: [PATCH tip/core/rcu 08/26] x86: Syscall hooks for userspace RCU extended QS

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Date:	Mon, 10 Sep 2012 23:30:37 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Josh Triplett <josh@...htriplett.org>
Cc:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org, mingo@...e.hu, laijs@...fujitsu.com,
	dipankar@...ibm.com, akpm@...ux-foundation.org,
	mathieu.desnoyers@...ymtl.ca, niv@...ibm.com, tglx@...utronix.de,
	peterz@...radead.org, rostedt@...dmis.org, Valdis.Kletnieks@...edu,
	dhowells@...hat.com, eric.dumazet@...il.com, darren@...art.com,
	sbw@....edu, patches@...aro.org,
	Alessio Igor Bogani <abogani@...nel.org>,
	Avi Kivity <avi@...hat.com>,
	Chris Metcalf <cmetcalf@...era.com>,
	Christoph Lameter <cl@...ux.com>,
	Geoff Levand <geoff@...radead.org>,
	Gilad Ben Yossef <gilad@...yossef.com>,
	Hakan Akkan <hakanakkan@...il.com>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...nel.org>,
	Kevin Hilman <khilman@...com>,
	Max Krasnyansky <maxk@...lcomm.com>,
	Stephen Hemminger <shemminger@...tta.com>,
	Sven-Thorsten Dietrich <thebigcorporation@...il.com>
Subject: Re: [PATCH tip/core/rcu 08/26] x86: Syscall hooks for userspace RCU
 extended QS

On Fri, Aug 31, 2012 at 04:59:10PM -0700, Josh Triplett wrote:
> On Thu, Aug 30, 2012 at 02:05:25PM -0700, Paul E. McKenney wrote:
> > From: Frederic Weisbecker <fweisbec@...il.com>
> > 
> > Add syscall slow path hooks to notify syscall entry
> > and exit on CPUs that want to support userspace RCU
> > extended quiescent state.
> > 
> > Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
> > Cc: Alessio Igor Bogani <abogani@...nel.org>
> > Cc: Andrew Morton <akpm@...ux-foundation.org>
> > Cc: Avi Kivity <avi@...hat.com>
> > Cc: Chris Metcalf <cmetcalf@...era.com>
> > Cc: Christoph Lameter <cl@...ux.com>
> > Cc: Geoff Levand <geoff@...radead.org>
> > Cc: Gilad Ben Yossef <gilad@...yossef.com>
> > Cc: Hakan Akkan <hakanakkan@...il.com>
> > Cc: H. Peter Anvin <hpa@...or.com>
> > Cc: Ingo Molnar <mingo@...nel.org>
> > Cc: Josh Triplett <josh@...htriplett.org>
> > Cc: Kevin Hilman <khilman@...com>
> > Cc: Max Krasnyansky <maxk@...lcomm.com>
> > Cc: Peter Zijlstra <peterz@...radead.org>
> > Cc: Stephen Hemminger <shemminger@...tta.com>
> > Cc: Steven Rostedt <rostedt@...dmis.org>
> > Cc: Sven-Thorsten Dietrich <thebigcorporation@...il.com>
> > Cc: Thomas Gleixner <tglx@...utronix.de>
> > Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> 
> This seems reasonable; presumably you plan to add something actually
> setting TIF_NOHZ in a subsequent patch series?

Yes, currently this is set by the selftests, see the combination of:

	[PATCH tip/core/rcu 07/26] rcu: Switch task's syscall hooks on context switch
	[PATCH tip/core/rcu 14/26] rcu: Userspace RCU extended QS selftest

Later this will be driven by the nohz subsystem.
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