Messages in this thread | | | From | Sunil Muthuswamy <> | Subject | RE: [PATCH net] hvsock: fix epollout hang from race condition | Date | Sat, 15 Jun 2019 07:23:29 +0000 |
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> -----Original Message----- > From: Dexuan Cui <decui@microsoft.com> > Sent: Friday, June 14, 2019 10:04 PM > To: David Miller <davem@davemloft.net>; Sunil Muthuswamy <sunilmut@microsoft.com> > Cc: KY Srinivasan <kys@microsoft.com>; Haiyang Zhang <haiyangz@microsoft.com>; Stephen Hemminger > <sthemmin@microsoft.com>; sashal@kernel.org; Michael Kelley <mikelley@microsoft.com>; netdev@vger.kernel.org; linux- > hyperv@vger.kernel.org; linux-kernel@vger.kernel.org > Subject: RE: [PATCH net] hvsock: fix epollout hang from race condition > > > From: linux-hyperv-owner@vger.kernel.org > > <linux-hyperv-owner@vger.kernel.org> On Behalf Of Dexuan Cui > > Sent: Friday, June 14, 2019 8:23 PM > > To: David Miller <davem@davemloft.net>; Sunil Muthuswamy > > <sunilmut@microsoft.com> > > Cc: KY Srinivasan <kys@microsoft.com>; Haiyang Zhang > > <haiyangz@microsoft.com>; Stephen Hemminger > > <sthemmin@microsoft.com>; sashal@kernel.org; Michael Kelley > > <mikelley@microsoft.com>; netdev@vger.kernel.org; > > linux-hyperv@vger.kernel.org; linux-kernel@vger.kernel.org > > Subject: RE: [PATCH net] hvsock: fix epollout hang from race condition > > > > > From: linux-hyperv-owner@vger.kernel.org > > > <linux-hyperv-owner@vger.kernel.org> On Behalf Of David Miller > > > Sent: Friday, June 14, 2019 7:15 PM > > > To: Sunil Muthuswamy <sunilmut@microsoft.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. > > Well, technically speaking, the warnings are caused by Suni's patch, but I think it should > be a bug of gcc (I'm using "gcc (Ubuntu 8.2.0-12ubuntu1) 8.2.0"). As you can see, the > line numbers given by gcc, i.e. line 205, line 406, are not related to the warnings. > > Actually, the same warnings can repro with the below one-line patch on this commit of > today's net.git: > 9a33629ba6b2 ("hv_netvsc: Set probe mode to sync") > > --- a/net/vmw_vsock/hyperv_transport.c > +++ b/net/vmw_vsock/hyperv_transport.c > @@ -403,6 +403,7 @@ static void hvs_open_connection(struct vmbus_channel *chan) > > set_per_channel_state(chan, conn_from_host ? new : sk); > vmbus_set_chn_rescind_callback(chan, hvs_close_connection); > + asm ("nop"); > > if (conn_from_host) { > new->sk_state = TCP_ESTABLISHED; > > It looks a simple inline assembly code can confuse gcc. I'm not sure if I should > report a bug for gcc... > > I posted a patch to suppress these bogus warnings just now. The Subject is: > > [PATCH net] hv_sock: Suppress bogus "may be used uninitialized" warnings > > Thanks, > -- Dexuan
Yes, these warnings are not specific to this patch. And, additionally these should already addressed in the commit https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git/commit/?id=ac383f58f3c98de37fa67452acc5bd677396e9f3 I was trying to avoid making the same changes here to avoid merge conflicts when 'net-next' merges with 'net' next.
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