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Date: Fri, 25 Aug 2017 13:37:18 +0800
From: Peter Xu <peterx@redhat.com>
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Subject: Re: [Qemu-devel] [RFC v2 4/8] QAPI: new QMP command option
 "without-bql"
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To: Fam Zheng <famz@redhat.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>, qemu-devel@nongnu.org, Paolo Bonzini <pbonzini@redhat.com>, "Daniel P . Berrange" <berrange@redhat.com>, Juan Quintela <quintela@redhat.com>, mdroth@linux.vnet.ibm.com, Eric Blake <eblake@redhat.com>, Laurent Vivier <lvivier@redhat.com>, Markus Armbruster <armbru@redhat.com>

On Thu, Aug 24, 2017 at 07:37:32AM +0800, Fam Zheng wrote:
> On Wed, 08/23 18:44, Dr. David Alan Gilbert wrote:
> > * Peter Xu (peterx@redhat.com) wrote:
> > > Introducing this new parameter for QMP commands in general to mark out
> > > when the command does not need BQL.  Normally QMP command executions are
> > > done with the protection of BQL in QEMU.  However the truth is that not
> > > all the QMP commands require the BQL.
> > > 
> > > This new parameter provides a way to allow QMP commands to run in
> > > parallel when possible, without the contention on the BQL.
> > > 
> > > Since the default value of "without-bql" is still false, so now all QMP
> > > commands are still protected by BQL still.
> > > 
> > > Signed-off-by: Peter Xu <peterx@redhat.com>
> > 
> > We should define what a 'without-bql' command is allowed to do:
> >    'Commands that have without-bql set _may_ be called without the bql
> >    being taken.  They must not take the bql or any other lock that may
> >    become dependent on the bql.'

Sure.

> >    (Do we need to say anything about RCU?)

Could I ask how is RCU related?

> > 
> > Also, 'no-bql' is shorter :-)
> 
> Or rather "need-bql" that defaults to true to avoid double negative (TM) with
> "no-bql = false"?

Ok let me use "need-bql". :)

-- 
Peter Xu