netdev - RE: [PATCH net] hvsock: fix epollout hang from race condition

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Date:   Sat, 15 Jun 2019 03:22:32 +0000
From:   Dexuan Cui <decui@...rosoft.com>
To:     David Miller <davem@...emloft.net>,
        Sunil Muthuswamy <sunilmut@...rosoft.com>
CC:     KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "sashal@...nel.org" <sashal@...nel.org>,
        Michael Kelley <mikelley@...rosoft.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH net] hvsock: fix epollout hang from race condition

> From: linux-hyperv-owner@...r.kernel.org
> <linux-hyperv-owner@...r.kernel.org> On Behalf Of David Miller
> Sent: Friday, June 14, 2019 7:15 PM
> To: Sunil Muthuswamy <sunilmut@...rosoft.com>
> 
> This adds lots of new warnings:
> 
> net/vmw_vsock/hyperv_transport.c: In function ‘hvs_probe’:
> net/vmw_vsock/hyperv_transport.c:205:20: warning: ‘vnew’ may be used
> uninitialized in this function [-Wmaybe-uninitialized]
>    remote->svm_port = host_ephemeral_port++;
>    ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
> net/vmw_vsock/hyperv_transport.c:332:21: note: ‘vnew’ was declared here
>   struct vsock_sock *vnew;
>                      ^~~~
> net/vmw_vsock/hyperv_transport.c:406:22: warning: ‘hvs_new’ may be
> used uninitialized in this function [-Wmaybe-uninitialized]
>    hvs_new->vm_srv_id = *if_type;
>    ~~~~~~~~~~~~~~~~~~~^~~~~~~~~~
> net/vmw_vsock/hyperv_transport.c:333:23: note: ‘hvs_new’ was declared
> here
>   struct hvsock *hvs, *hvs_new;
>                        ^~~~~~~

Hi David,
These warnings are not introduced by this patch from Sunil.

I'm not sure why I didn't notice these warnings before.  
Probably my gcc version is not new eought? 

Actually these warnings are bogus, as I checked the related functions,
which may confuse the compiler's static analysis.

I'm going to make a patch to initialize the pointers to NULL to suppress
the warnings. My patch will be based on the latest's net.git + this patch
from Sunil.

Thanks,
-- Dexuan