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Re: [Xen-devel] gfn_lock() seems useless.



On Tue, Feb 02, 2016 at 08:55:50PM -0800, Andres Lagar Cavilla wrote:
> At the time, I had a patch queue for splitting the p2m locking into a tree
> of per-2M locks. Very similar to Linux's split locks. I scaffolded the
> macros to allow for that expansion. Then, I got pulled onto other things.

Could you post/point folks to your patch queue?

Thanks.
> 
> Andres
> 
> On Tue, Feb 2, 2016 at 8:26 AM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
> 
> > >>> On 02.02.16 at 07:54, <oscar.zhangbo@xxxxxxxxxx> wrote:
> > > Hi all:
> > > In patch e1e40bccee7490a01ac7d1f759ec2bbafd3c7185, it says that"many
> > > routines can logically assert holding the p2m *FOR A SPECIFIC GFN.*" ,
> > > But I find out that it did nothing for locking a single gfn, in fact  it
> > > still locked the entire p2m list.
> > >
> > > -#define p2m_lock_recursive(p) mm_lock_recursive(p2m, &(p)->lock)
> > > +#define gfn_lock(p,g,o)       mm_lock_recursive(p2m, &(p)->lock)  //'g'
> > is not
> > > used. The entire p2m list is locked.
> > >
> > >
> > > Do we have any plan to lock a specific gfn?
> >
> > This indeed is a long term plan, but afaik no-one is currently
> > doing any work in that direction.
> >
> > Jan
> >
> >

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