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.f...@gmail.com> > Signed-off-by: Pan Xinhui <xinhui....@linux.vnet.ibm.com> > --- > 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. _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
