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Re: [Qemu-devel] [PATCH] virtio_ring: use smp_store_mb
From: |
Peter Zijlstra |
Subject: |
Re: [Qemu-devel] [PATCH] virtio_ring: use smp_store_mb |
Date: |
Thu, 17 Dec 2015 11:52:38 +0100 |
User-agent: |
Mutt/1.5.21 (2012-12-30) |
On Thu, Dec 17, 2015 at 12:32:53PM +0200, Michael S. Tsirkin wrote:
> +static inline void virtio_store_mb(bool weak_barriers,
> + __virtio16 *p, __virtio16 v)
> +{
> +#ifdef CONFIG_SMP
> + if (weak_barriers)
> + smp_store_mb(*p, v);
> + else
> +#endif
> + {
> + WRITE_ONCE(*p, v);
> + mb();
> + }
> +}
This is a different barrier depending on SMP, that seems wrong.
smp_mb(), as (should be) used by smp_store_mb() does not provide a
barrier against IO. mb() otoh does.
Since this is virtIO I would expect you always want mb().
- [Qemu-devel] [PATCH] virtio_ring: use smp_store_mb, Michael S. Tsirkin, 2015/12/17
- Re: [Qemu-devel] [PATCH] virtio_ring: use smp_store_mb,
Peter Zijlstra <=
- Re: [Qemu-devel] [PATCH] virtio_ring: use smp_store_mb, Michael S. Tsirkin, 2015/12/17
- Re: [Qemu-devel] [PATCH] virtio_ring: use smp_store_mb, Peter Zijlstra, 2015/12/17
- Re: [Qemu-devel] [PATCH] virtio_ring: use smp_store_mb, Michael S. Tsirkin, 2015/12/17
- Re: [Qemu-devel] [PATCH] virtio_ring: use smp_store_mb, Peter Zijlstra, 2015/12/17
- Re: [Qemu-devel] [PATCH] virtio_ring: use smp_store_mb, Michael S. Tsirkin, 2015/12/17
- [Qemu-devel] new barrier type for paravirt (was Re: [PATCH] virtio_ring: use smp_store_mb), Michael S. Tsirkin, 2015/12/20
- Re: [Qemu-devel] [Xen-devel] new barrier type for paravirt (was Re: [PATCH] virtio_ring: use smp_store_mb), Andrew Cooper, 2015/12/20
- Re: [Qemu-devel] [Xen-devel] new barrier type for paravirt (was Re: [PATCH] virtio_ring: use smp_store_mb), Peter Zijlstra, 2015/12/20
- Re: [Qemu-devel] [Xen-devel] new barrier type for paravirt (was Re: [PATCH] virtio_ring: use smp_store_mb), Michael S. Tsirkin, 2015/12/21
- [Qemu-devel] [PATCH RFC] smp_store_mb should use smp_mb, Michael S. Tsirkin, 2015/12/21