From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH 2/2] tools/virtio: make barriers stronger. Date: Wed, 6 Mar 2013 12:20:17 +0200 Message-ID: <20130306102017.GB16921@redhat.com> References: <1362491468-16681-1-git-send-email-sjur.brandeland@stericsson.com> <871ubtcezb.fsf@rustcorp.com.au> <87y5e1b03l.fsf@rustcorp.com.au> <87vc95b019.fsf@rustcorp.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <87vc95b019.fsf@rustcorp.com.au> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Rusty Russell Cc: sjur@brendeland.net, Linus Walleij , Erwan Yvin , virtualization@lists.linux-foundation.org, sjur.brandeland@stericsson.com List-Id: virtualization@lists.linuxfoundation.org On Wed, Mar 06, 2013 at 03:54:42PM +1100, Rusty Russell wrote: > In the coming vringh_test, we share an mmap with another userspace process > for testing. This requires real barriers. > > Signed-off-by: Rusty Russell > > diff --git a/tools/virtio/asm/barrier.h b/tools/virtio/asm/barrier.h > index aff61e1..7a63693 100644 > --- a/tools/virtio/asm/barrier.h > +++ b/tools/virtio/asm/barrier.h > @@ -3,8 +3,8 @@ > #define mb() __sync_synchronize() > > #define smp_mb() mb() > -# define smp_rmb() barrier() > -# define smp_wmb() barrier() > +# define smp_rmb() mb() > +# define smp_wmb() mb() > /* Weak barriers should be used. If not - it's a bug */ > # define rmb() abort() > # define wmb() abort() Hmm this seems wrong on x86 which has strong order in hardware. It should not matter whether the other side is a userspace process or a kernel thread. -- MST