linux-kernel - Re: [PATCH net-next 12/12] tools/virtio: fix smp

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Date:   Fri, 26 Jan 2018 11:56:14 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>, linux-kernel@...r.kernel.org
Cc:     netdev@...r.kernel.org, John Fastabend <john.fastabend@...il.com>,
        David Miller <davem@...emloft.net>,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH net-next 12/12] tools/virtio: fix smp_mb on x86



On 2018年01月26日 07:36, Michael S. Tsirkin wrote:
> Offset 128 overlaps the last word of the redzone.
> Use 132 which is always beyond that.
>
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> ---
>   tools/virtio/ringtest/main.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/virtio/ringtest/main.h b/tools/virtio/ringtest/main.h
> index 593a328..301d59b 100644
> --- a/tools/virtio/ringtest/main.h
> +++ b/tools/virtio/ringtest/main.h
> @@ -111,7 +111,7 @@ static inline void busy_wait(void)
>   }
>   
>   #if defined(__x86_64__) || defined(__i386__)
> -#define smp_mb()     asm volatile("lock; addl $0,-128(%%rsp)" ::: "memory", "cc")

Just wonder did "rsp" work for __i386__ ?

Thanks

> +#define smp_mb()     asm volatile("lock; addl $0,-132(%%rsp)" ::: "memory", "cc")
>   #else
>   /*
>    * Not using __ATOMIC_SEQ_CST since gcc docs say they are only synchronized