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Date: Tue, 18 Jun 2013 14:25:07 +0200
From: Stefan Hajnoczi <stefanha@gmail.com>
Message-ID: <20130618122507.GI7649@stefanha-thinkpad.redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v2 2/6] net: introduce lock to protect
 NetClientState's peer's access
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To: Liu Ping Fan <qemulist@gmail.com>
Cc: qemu-devel@nongnu.org, Stefan Hajnoczi <stefanha@redhat.com>, mdroth <mdroth@linux.vnet.ibm.com>

On Thu, Jun 13, 2013 at 05:03:02PM +0800, Liu Ping Fan wrote:
> @@ -67,6 +67,10 @@ struct NetClientState {
>      NetClientInfo *info;
>      int link_down;
>      QTAILQ_ENTRY(NetClientState) next;
> +    /* protect the race access of peer only between reader and writer.
> +         * to resolve the writer's race condition, resort on biglock.
> +         */

Indentation

> @@ -301,6 +303,38 @@ static void qemu_free_net_client(NetClientState *nc)
>      }
>  }
>  
> +/* elimate the reference and sync with exit of rx/tx action.

s/elimate/Eliminate/

> + * And flush out peer's queue.
> + */
> +static void qemu_net_client_detach_flush(NetClientState *nc)
> +{
> +    NetClientState *peer;
> +
> +    /* reader of self's peer field , fixme? the deleters are not concurrent,
> +         * so this pair lock can save.
> +         */

Indentation, also please resolve the fixme.

> @@ -394,6 +433,28 @@ int qemu_can_send_packet(NetClientState *sender)
>      return 1;
>  }
>  
> +int qemu_can_send_packet(NetClientState *sender)
> +{
> +    int ret = 1;
> +
> +    qemu_mutex_lock(&sender->peer_lock);
> +    if (!sender->peer) {
> +        goto unlock;
> +    }
> +
> +    if (sender->peer->receive_disabled) {
> +        ret = 0;
> +        goto unlock;
> +    } else if (sender->peer->info->can_receive &&
> +               !sender->peer->info->can_receive(sender->peer)) {
> +        ret = 0;
> +        goto unlock;
> +    }

Just call qemu_can_send_packet_nolock() instead of duplicating code?