linux-kernel - Re: [PATCH rcu/urgent] Banishing kthreads

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Date:	Fri, 17 Jun 2011 16:35:23 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
CC:	linux-kernel@...r.kernel.org, mingo@...e.hu, laijs@...fujitsu.com,
	dipankar@...ibm.com, akpm@...ux-foundation.org,
	josh@...htriplett.org, 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,
	patches@...aro.org
Subject: Re: [PATCH rcu/urgent] Banishing kthreads

* Paul E. McKenney (paulmck@...ux.vnet.ibm.com) wrote:
> This patchset banishes RCU kthreads from non-RCU_BOOST kernel threads.
> The two patches are as follows:
> 
> 1.	Minimal patch that #ifdefs out the kthread code.
> 
> 2.	Code-movement patch that puts the code #ifdefed out above
> 	under existing #ifdefs in kernel/rcutree_plugin.h.

Hi Paul,

I'm wondering about the impact of this change: so I guess that before
the change, it was OK to go on a waitqueue (might_sleep()) within a
call_rcu callback, but since the execution now moves to a softirq
handler in non-RCU_BOOST kernels, it's not allowed anymore. I might be
missing something though: was sleeping within call_rcu handlers already
prohibited ? (never had to sleep in those, so I never had to check if it
was allowed)

Thanks,

Mathieu

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
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