netdev - Re: [PATCHv2] xen-netfront: remove warning when unloading module

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Message-Id: <20171128.042254.1904551835549520772.davem@davemloft.net>
Date:   Tue, 28 Nov 2017 04:22:54 +0900 (KST)
From:   David Miller <davem@...emloft.net>
To:     otubo@...hat.com
Cc:     xen-devel@...ts.xenproject.org, netdev@...r.kernel.org,
        paul.durrant@...rix.com, wei.liu2@...rix.com,
        linux-kernel@...r.kernel.org, vkuznets@...hat.com,
        cavery@...hat.com, cheshi@...hat.com, mgamal@...hat.com,
        jgross@...e.com, boris.ostrovsky@...cle.com
Subject: Re: [PATCHv2] xen-netfront: remove warning when unloading module

From: Eduardo Otubo <otubo@...hat.com>
Date: Thu, 23 Nov 2017 15:18:35 +0100

> v2:
>  * Replace busy wait with wait_event()/wake_up_all()
>  * Cannot garantee that at the time xennet_remove is called, the
>    xen_netback state will not be XenbusStateClosed, so added a
>    condition for that
>  * There's a small chance for the xen_netback state is
>    XenbusStateUnknown by the time the xen_netfront switches to Closed,
>    so added a condition for that.
> 
> When unloading module xen_netfront from guest, dmesg would output
> warning messages like below:
> 
>   [  105.236836] xen:grant_table: WARNING: g.e. 0x903 still in use!
>   [  105.236839] deferring g.e. 0x903 (pfn 0x35805)
> 
> This problem relies on netfront and netback being out of sync. By the time
> netfront revokes the g.e.'s netback didn't have enough time to free all of
> them, hence displaying the warnings on dmesg.
> 
> The trick here is to make netfront to wait until netback frees all the g.e.'s
> and only then continue to cleanup for the module removal, and this is done by
> manipulating both device states.
> 
> Signed-off-by: Eduardo Otubo <otubo@...hat.com>

Applied, thank you.