On Sun, Aug 28, 2016 at 01:56:13PM +0200, Manfred Spraul wrote: > Right now, the spinlock machinery tries to guarantee barriers even for > unorthodox locking cases, which ends up as a constant stream of updates > as the architectures try to support new unorthodox ideas. > > The patch proposes to reverse that: > spin_lock is ACQUIRE, spin_unlock is RELEASE. > spin_unlock_wait is also ACQUIRE. > Code that needs further guarantees must use appropriate explicit barriers. > > Architectures that can implement some barriers for free can define the > barriers as NOPs. > > As the initial step, the patch converts ipc/sem.c to the new defines: > - no more smp_rmb() after spin_unlock_wait(), that is part of > spin_unlock_wait() > - smp_mb__after_spin_lock() instead of a direct smp_mb(). >
Why? This does not explain why..
