From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ingo Molnar <mingo@elte.hu>
Subject: Re: [PATCH 4/6] kvm tools: Add rwlock wrapper
Date: Sun, 29 May 2011 09:19:48 +0200
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Cc: Sasha Levin <levinsasha928@gmail.com>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Pekka Enberg <penberg@kernel.org>, john@jfloren.net,
	kvm@vger.kernel.org, asias.hejun@gmail.com, gorcunov@gmail.com,
	prasadjoshi124@gmail.com,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Avi Kivity <avi@redhat.com>
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* Avi Kivity <avi@redhat.com> wrote:

> Yes, this is equivalent to the kernel's stop_machine_run().  It's a 
> heavyweight method but it should work just fine.

Yeah. It is fine for reconfiguration/configuration-only kind of write 
paths - i.e. the mmio lookup path should be ok.

There's only one thing i'd like to warn about: please still shape it 
as a br_read_lock()/unlock(), br_write_lock()/unlock() operation.

This way all the SMP read paths remain identified properly, even if 
br_write_lock() does a stop_machine_run() equivalent. This still 
leaves options open for an easy conversion to rwlock or urcu (should 
any particular write path become more than just occasional).

Thanks,

	Ingo