linux-kernel - Re: [RFC PATCH] introduce sys_membarrier(): process-wide memory barrier (v3a)

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Date:	Mon, 11 Jan 2010 22:19:17 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Cc:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Oleg Nesterov <oleg@...hat.com>, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...e.hu>, akpm@...ux-foundation.org,
	josh@...htriplett.org, tglx@...utronix.de, Valdis.Kletnieks@...edu,
	dhowells@...hat.com, laijs@...fujitsu.com, dipankar@...ibm.com,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [RFC PATCH] introduce sys_membarrier(): process-wide memory
 barrier (v3a)

On Mon, 2010-01-11 at 15:52 -0500, Mathieu Desnoyers wrote:
> 
> So the clear bit can occur far, far away in the future, we don't care.
> We'll just send extra IPIs when unneeded in this time-frame.

I think we should try harder not to disturb CPUs, particularly in the
face of RT tasks and DoS scenarios. Therefore I don't think we should
just wildly send to mm_cpumask(), but verify (although speculatively)
that the remote tasks' mm matches ours.



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