From mboxrd@z Thu Jan  1 00:00:00 1970
From: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Subject: Re: [PATCH] vhost: fix connect hang in client mode
Date: Thu, 21 Jul 2016 17:37:14 +0800
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Cc: dev@dpdk.org, Huawei Xie <huawei.xie@intel.com>,
 Dyasly Sergey <s.dyasly@samsung.com>,
 Heetae Ahn <heetae82.ahn@samsung.com>,
 Thomas Monjalon <thomas.monjalon@6wind.com>
To: Ilya Maximets <i.maximets@samsung.com>
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On Thu, Jul 21, 2016 at 11:21:15AM +0300, Ilya Maximets wrote:
> If something abnormal happened to QEMU, 'connect()' can block calling
> thread (e.g. main thread of OVS) forever or for a really long time.
> This can break whole application or block the reconnection thread.
> 
> Example with OVS:
> 
> 	ovs_rcu(urcu2)|WARN|blocked 512000 ms waiting for main to quiesce
> 	(gdb) bt
> 	#0  connect () from /lib64/libpthread.so.0
> 	#1  vhost_user_create_client (vsocket=0xa816e0)
> 	#2  rte_vhost_driver_register
> 	#3  netdev_dpdk_vhost_user_construct
> 	#4  netdev_open (name=0xa664b0 "vhost1")
> 	[...]
> 	#11 main
> 
> Fix that by setting non-blocking mode for client sockets for connection.
> 
> Fixes: 64ab701c3d1e ("vhost: add vhost-user client mode")

Thanks for spotting and fixing yet another bug!

>  
> +static int
> +vhost_user_connect_nonblock(int fd, struct sockaddr *un, size_t sz)

I don't quite understand why this is needed: connect() with O_NONBLOCK
flag set is not enough?

	--yliu