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Date: Mon, 4 Mar 2013 16:19:15 +0100
From: Stefan Hajnoczi <stefanha@gmail.com>
Message-ID: <20130304151915.GA16196@stefanha-thinkpad.redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 3/3] net: make netclient re-entrant with
	refcnt
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To: Liu Ping Fan <qemulist@gmail.com>
Cc: mdroth <mdroth@linux.vnet.ibm.com>, Paolo Bonzini <pbonzini@redhat.com>, qemu-devel@nongnu.org, Anthony Liguori <anthony@codemonkey.ws>, "Michael S. Tsirkin" <mst@redhat.com>

On Sun, Mar 03, 2013 at 09:21:22PM +0800, Liu Ping Fan wrote:
> diff --git a/net/hub.c b/net/hub.c
> index 97c3ac3..ab4448e 100644
> --- a/net/hub.c
> +++ b/net/hub.c
> @@ -36,6 +36,7 @@ typedef struct NetHubPort {
>  } NetHubPort;
>  
>  struct NetHub {
> +    QemuMutex lock;

Please document what this lock protects.  I think it only protects the
ports list.

> diff --git a/net/net.c b/net/net.c
> index 0acb933..5a8bb6a 100644
> --- a/net/net.c
> +++ b/net/net.c
> @@ -45,6 +45,7 @@
>  # define CONFIG_NET_BRIDGE
>  #endif
>  
> +static QemuMutex net_clients_lock;
>  static QTAILQ_HEAD(, NetClientState) net_clients;

I'm not sure what net_clients_lock protects since this lock is not taken
by all net_clients users.

The lock should be destroyed in net_cleanup().

This should be a separate patch that fully explains the purpose of the
lock and uses it consistently in net.c.