linux-kernel - Re: [PATCH RFC] v2 expedited "big hammer" RCU grace periods

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Message-ID: <20090427205601.GA5716@ioremap.net>
Date:	Tue, 28 Apr 2009 00:56:02 +0400
From:	Evgeniy Polyakov <zbr@...emap.net>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Cc:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, netfilter-devel@...r.kernel.org,
	akpm@...ux-foundation.org, torvalds@...ux-foundation.org,
	davem@...emloft.net, dada1@...mosbay.com,
	jeff.chua.linux@...il.com, paulus@...ba.org, laijs@...fujitsu.com,
	jengelh@...ozas.de, r000n@...0n.net, benh@...nel.crashing.org
Subject: Re: [PATCH RFC] v2 expedited "big hammer" RCU grace periods

Hi.

On Mon, Apr 27, 2009 at 11:54:24AM -0400, Mathieu Desnoyers (mathieu.desnoyers@...ymtl.ca) wrote:
> It might sound a bit simplistic, but... scheduling a high-priority
> workqueue on every CPUs would give you the guarantees you seem to need
> here. Or is the delay of letting the scheduler schedule a high-priority
> task a delay you are trying to avoid ?

I believe not the abstract (empty) task should be invoked, but a real
task which does the work. Presumably if we want to schedule a way
networking part to copy its counters, system should wake up the
appropriate userspace thread blocked in a grace-period waking path, so
effectively either RCU callback processing code or some registered
thread should be awakened.

Just a detail though.

-- 
	Evgeniy Polyakov
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