linux-kernel - Re: [PATCH v2 1/2] workqueue: add quiescent state between work items

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Message-ID: <20141007134528.1a59f31b@jlaw-desktop.mno.stratus.com>
Date:	Tue, 7 Oct 2014 13:45:28 -0400
From:	Joe Lawrence <joe.lawrence@...atus.com>
To:	<paulmck@...ux.vnet.ibm.com>
CC:	Jiri Pirko <jiri@...nulli.us>, Tejun Heo <tj@...nel.org>,
	<linux-kernel@...r.kernel.org>, <stable@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] workqueue: add quiescent state between work
 items

On Tue, 7 Oct 2014 06:43:29 -0700
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> wrote:

> On Tue, Oct 07, 2014 at 09:29:42AM +0200, Jiri Pirko wrote:
[ ... snip ... ]
> > 
> > Paul, Tehun, how do you propose to fix this on older kernels which do
> > not have rcu_note_voluntary_context_switch? I'm particullary interested
> > in 3.10.
> 
> Hello, Jiri,
> 
> Older kernels can instead use rcu_note_context_switch().

Hi Paul,

Does 4a81e8328d37 ("rcu: Reduce overhead of cond_resched() checks for
RCU") affect a backport to 3.10?

I noticed that rcu_note_context_switch added a call to
rcu_momentary_dyntick_idle in that change, which is only present in
v3.16+.

Would rcu_note_context_switch be effective by itself on a 3.10 kernel?

Thanks,

-- Joe
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