On Thu, May 26, 2016 at 06:47:29PM +0200, Peter Zijlstra wrote: > On Wed, May 25, 2016 at 04:18:08PM +0800, Pan Xinhui wrote: > > cmpxchg_release is light-wight than cmpxchg, we can gain a better > > performace then. On some arch like ppc, barrier impact the performace > > too much. > > > > Suggested-by: Boqun Feng <boqun.feng@xxxxxxxxx> > > Signed-off-by: Pan Xinhui <xinhui.pan@xxxxxxxxxxxxxxxxxx> > > --- > > kernel/locking/qspinlock_paravirt.h | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/kernel/locking/qspinlock_paravirt.h b/kernel/locking/qspinlock_paravirt.h > > index a5b1248..2bbffe4 100644 > > --- a/kernel/locking/qspinlock_paravirt.h > > +++ b/kernel/locking/qspinlock_paravirt.h > > @@ -614,7 +614,7 @@ __visible void __pv_queued_spin_unlock(struct qspinlock *lock) > > * unhash. Otherwise it would be possible to have multiple @lock > > * entries, which would be BAD. > > */ > > - locked = cmpxchg(&l->locked, _Q_LOCKED_VAL, 0); > > + locked = cmpxchg_release(&l->locked, _Q_LOCKED_VAL, 0); > > if (likely(locked == _Q_LOCKED_VAL)) > > return; > > This patch fails to explain _why_ it can be relaxed. > > And seeing how this cmpxchg() can actually unlock the lock, I don't see > how this can possibly be correct. Maybe cmpxchg_release(), but relaxed > seems very wrong. Clearly I need to stop working for the day, I cannea read. You're doing release, not relaxed. Still Changelog needs improvement. _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
