linux-kernel - RE: [PATCH 1/1] Drivers: hv: util: on deinit, don't wait the release event, if we shouldn't

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Date:   Wed, 1 Mar 2017 14:31:36 +0000
From:   Dexuan Cui <decui@...rosoft.com>
To:     KY Srinivasan <kys@...rosoft.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
        "olaf@...fle.de" <olaf@...fle.de>,
        "apw@...onical.com" <apw@...onical.com>,
        "vkuznets@...hat.com" <vkuznets@...hat.com>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        "leann.ogasawara@...onical.com" <leann.ogasawara@...onical.com>
CC:     Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>
Subject: RE: [PATCH 1/1] Drivers: hv: util: on deinit, don't wait the release
 event, if we shouldn't

> From: kys@...hange.microsoft.com [mailto:kys@...hange.microsoft.com]
> Sent: Tuesday, February 28, 2017 07:18
> To: gregkh@...uxfoundation.org; linux-kernel@...r.kernel.org;
> ...
> From: Dexuan Cui <decui@...rosoft.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@...rosoft.com>
> ...

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

Thanks,
-- Dexuan