Re: [Xen-devel] [v3,11/41] mips: reuse asm-generic/barrier.h

[Leonid Yegoshin <Leonid.Yegoshin@xxxxxxxxxx>]

On 01/14/2016 08:16 AM, Paul E. McKenney wrote:
> On Thu, Jan 14, 2016 at 12:04:45PM +0000, Will Deacon wrote:
> > On Wed, Jan 13, 2016 at 12:58:22PM -0800, Leonid Yegoshin wrote:
> > > On 01/13/2016 12:48 PM, Peter Zijlstra wrote:
> > > > On Wed, Jan 13, 2016 at 11:02:35AM -0800, Leonid Yegoshin wrote:
> > > >
> > > > > I ask HW team about it but I have a question - has it any relationship with
> > > > > replacing MIPS SYNC with lightweight SYNCs (SYNC_WMB etc)?
> > > > Of course. If you cannot explain the semantics of the primitives you
> > > > introduce, how can we judge the patch.
> > > You missed a point - it is a question about replacement of SYNC with
> > > lightweight primitives. It is NOT a question about multithread system
> > > behavior without any SYNC. The answer on a latest Will's question lies in
> > > different area.
> What Will said!
>
> Yes, you can cut corners within MIPS architecture-specific code,
> but primitives that are used in the core kernel really do need to
> work as expected.
>
>                                                         Thanx, Paul
Absolutelly! Please use SYNC - right now it is not.

An the only point - please use an appropriate SYNC_* barriers instead of 
heavy bold hammer. That stuff was design explicitly to support the 
requirements of Documentation/memory-barriers.txt
It is easy - just use smp_acquire instead of plain smp_mb 
insmp_load_acquire, at least for MIPS.
- Leonid.
- Leonid.

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