Re: [PATCH] rwsem: fix missed wakeup due to reordering of load

[Peter Zijlstra]

On Thu, Jul 27, 2017 at 11:48:53AM -0400, Waiman Long wrote:
> atomic_long_sub_return_release() is implmented.

I've not had time to really thing about the problem at hand, but this I
can answer:

TSO (x86, s390, sparc): fully serialized
PPC: lwsync; ll/sc	(RCpc)
ARM64: ll/sc-release	(RCsc)
other: smp_mb(); atomic_sub_return_relaxed();