On 01/14/2016 08:16 AM, Paul E. McKenney wrote:

On Thu, Jan 14, 2016 at 12:04:45PM +0000, Will Deacon wrote:

quoted

On Wed, Jan 13, 2016 at 12:58:22PM -0800, Leonid Yegoshin wrote:

quoted

On 01/13/2016 12:48 PM, Peter Zijlstra wrote:

quoted

On Wed, Jan 13, 2016 at 11:02:35AM -0800, Leonid Yegoshin wrote:

quoted

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.