linux-kernel - RE: [PATCH] Drivers: hv: vmbus: prevent new subchannel creation on device shutdown

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Date:	Thu, 16 Jul 2015 00:31:06 +0000
From:	KY Srinivasan <kys@...rosoft.com>
To:	Vitaly Kuznetsov <vkuznets@...hat.com>,
	Dexuan Cui <decui@...rosoft.com>
CC:	"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
	"Haiyang Zhang" <haiyangz@...rosoft.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] Drivers: hv: vmbus: prevent new subchannel creation on
 device shutdown



> -----Original Message-----
> From: Vitaly Kuznetsov [mailto:vkuznets@...hat.com]
> Sent: Tuesday, July 14, 2015 9:03 AM
> To: Dexuan Cui
> Cc: devel@...uxdriverproject.org; KY Srinivasan; Haiyang Zhang; linux-
> kernel@...r.kernel.org
> Subject: Re: [PATCH] Drivers: hv: vmbus: prevent new subchannel creation
> on device shutdown
> 
> Dexuan Cui <decui@...rosoft.com> writes:
> 
> >> -----Original Message-----
> >> From: Vitaly Kuznetsov
> >> Sent: Monday, July 13, 2015 20:19
> >> Subject: [PATCH] Drivers: hv: vmbus: prevent new subchannel creation on
> device
> >> shutdown
> >>
> >> When a new subchannel offer from host comes during device shutdown
> (e.g.
> >> when a netvsc/storvsc module is unloadedshortly after it was loaded) a
> >> crash can happen as vmbus_process_offer() is not anyhow serialized with
> >> vmbus_remove().
> >
> > How about vmbus_onoffer_rescind()?
> > It's not serialized with vmbus_remove() either, so I think there is an issue
> too?
> >
> > I remember when 'rmmod hv_netvsc', we get a rescind-offer message for
> > each subchannel.
> >
> 
> True, I think we have a race with rescind messages as well, we just
> never saw crashes for some reason. I'll think how we can make the fix
> more general.

In an earlier email I had outlined how I was planning to address original issue. I have a patch based on the logic
I had described - essentially put the burden on the probe call to ensure that the open (including sub-channels) is
complete before we return from probe. I will post this shortly.

Regards,

K. Y
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