Re: spin_lock implicit/explicit memory barrier

[Peter Zijlstra]

On Wed, Aug 10, 2016 at 04:29:22PM -0700, Davidlohr Bueso wrote:

> (1) As Manfred suggested, have a patch 1 that fixes the race against mainline
> with the redundant smp_rmb, then apply a second patch that gets rid of it
> for mainline, but only backport the original patch 1 down to 3.12.

I have not followed the thread closely, but this seems like the best
option. Esp. since 726328d92a42 ("locking/spinlock, arch: Update and fix
spin_unlock_wait() implementations") is incomplete, it relies on at
least 6262db7c088b ("powerpc/spinlock: Fix spin_unlock_wait()") to sort
PPC.