Re: Memory-ordering recipes

[Peter Zijlstra]

On Sun, Sep 17, 2017 at 04:05:09PM -0700, Paul E. McKenney wrote:

> So what litmus tests are needed?  Here is my initial set:
> 
> 1.	Release-acquire chains, AKA ISA2, Z6.2, LB, and 3.LB
> 
> 	Lots of variety here, can in some cases substitute:
> 	
> 	a.	READ_ONCE() for smp_load_acquire()
> 	b.	WRITE_ONCE() for smp_store_release()
> 	c.	Dependencies for both smp_load_acquire() and
> 		smp_store_release().
> 	d.	smp_wmb() for smp_store_release() in first thread
> 		of ISA2 and Z6.2.
> 	e.	smp_rmb() for smp_load_acquire() in last thread of ISA2.
> 
> 2.	MP (see test6.pdf for nickname translation)
> 
> 	a.	smp_store_release() / smp_load_acquire()
> 	b.	rcu_assign_pointer() / rcu_dereference()
> 	c.	smp_wmb() / smp_rmb()
> 	d.	Replacing either of the above with smp_mb()
> 
> 3.	SB
> 
> 	a.	smp_mb(), as in lockless wait-wakeup coordination.
> 		And as in sys_membarrier()-scheduler coordination,
> 		for that matter.
> 
> Others?

So I have no idea what you're proposing here. The above is just a bunch
of words without meaning :-(