From: Dexuan Cui <decui@microsoft.com>
To: KY Srinivasan <kys@microsoft.com>,
        "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "devel@linuxdriverproject.org" <devel@linuxdriverproject.org>,
        "olaf@aepfle.de" <olaf@aepfle.de>,
        "apw@canonical.com" <apw@canonical.com>,
        "vkuznets@redhat.com" <vkuznets@redhat.com>,
        "jasowang@redhat.com" <jasowang@redhat.com>,
        "leann.ogasawara@canonical.com" <leann.ogasawara@canonical.com>
CC: Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>
Subject: RE: [PATCH 1/1] Drivers: hv: util: on deinit, don't wait the release
 event, if we shouldn't
Thread-Topic: [PATCH 1/1] Drivers: hv: util: on deinit, don't wait the release
 event, if we shouldn't
Thread-Index: AQHSkU/kJuR7/+sJ10uJiLyUeQ36BKGACIkw
Date: Wed, 1 Mar 2017 14:31:36 +0000
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> From: kys@exchange.microsoft.com [mailto:kys@exchange.microsoft.com]
> Sent: Tuesday, February 28, 2017 07:18
> To: gregkh@linuxfoundation.org; linux-kernel@vger.kernel.org;
> ...
> From: Dexuan Cui <decui@microsoft.com>
> 
> If the daemon is NOT running at all, when we disable the util device from
> Hyper-V Manager (or sometimes the host can rescind a util device and then
> re-offer it), we'll hang in util_remove -> hv_kvp_deinit ->
> wait_for_completion(&release_event), because this code path doesn't run:
> hvt_op_release -> ... -> kvp_on_reset -> complete(&release_event).
> 
> Due to this, we even can't reboot the VM properly.
> 
> The patch tracks if the dev file is opened or not, and we only need to
> wait if it's opened.
> 
> Fixes: 5a66fecbf6aa ("Drivers: hv: util: kvp: Fix a rescind processing issue")
> 
> Signed-off-by: Dexuan Cui <decui@microsoft.com>
> ...

Please ignore this patch, since Vitaly posted a better fix instead.

Thanks,
-- Dexuan