From: Greg KH <gregkh@linuxfoundation.org>
To: kys@microsoft.com
Cc: linux-kernel@vger.kernel.org, devel@linuxdriverproject.org,
olaf@aepfle.de, apw@canonical.com, jasowang@redhat.com,
sthemmin@microsoft.com, Michael.H.Kelley@microsoft.com,
vkuznets@redhat.com, Haiyang Zhang <haiyangz@microsoft.com>,
stable@vger.kernel.org
Subject: Re: [PATCH 2/2] Drivers: hv: vmbus: offload the handling of channels to two workqueues
Date: Mon, 26 Nov 2018 20:35:03 +0100 [thread overview]
Message-ID: <20181126193503.GA25649@kroah.com> (raw)
In-Reply-To: <20181126022958.11320-2-kys@linuxonhyperv.com>
On Mon, Nov 26, 2018 at 02:29:57AM +0000, kys@linuxonhyperv.com wrote:
> From: Dexuan Cui <decui@microsoft.com>
>
> vmbus_process_offer() mustn't call channel->sc_creation_callback()
> directly for sub-channels, because sc_creation_callback() ->
> vmbus_open() may never get the host's response to the
> OPEN_CHANNEL message (the host may rescind a channel at any time,
> e.g. in the case of hot removing a NIC), and vmbus_onoffer_rescind()
> may not wake up the vmbus_open() as it's blocked due to a non-zero
> vmbus_connection.offer_in_progress, and finally we have a deadlock.
>
> The above is also true for primary channels, if the related device
> drivers use sync probing mode by default.
>
> And, usually the handling of primary channels and sub-channels can
> depend on each other, so we should offload them to different
> workqueues to avoid possible deadlock, e.g. in sync-probing mode,
> NIC1's netvsc_subchan_work() can race with NIC2's netvsc_probe() ->
> rtnl_lock(), and causes deadlock: the former gets the rtnl_lock
> and waits for all the sub-channels to appear, but the latter
> can't get the rtnl_lock and this blocks the handling of sub-channels.
>
> The patch can fix the multiple-NIC deadlock described above for
> v3.x kernels (e.g. RHEL 7.x) which don't support async-probing
> of devices, and v4.4, v4.9, v4.14 and v4.18 which support async-probing
> but don't enable async-probing for Hyper-V drivers (yet).
>
> The patch can also fix the hang issue in sub-channel's handling described
> above for all versions of kernels, including v4.19 and v4.20-rc3.
>
> So the patch should be applied to all the existing kernels.
>
> Fixes: 8195b1396ec8 ("hv_netvsc: fix deadlock on hotplug")
> Cc: stable@vger.kernel.org
> Cc: Stephen Hemminger <sthemmin@microsoft.com>
> Cc: K. Y. Srinivasan <kys@microsoft.com>
> Cc: Haiyang Zhang <haiyangz@microsoft.com>
> Signed-off-by: Dexuan Cui <decui@microsoft.com>
> Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
> ---
> drivers/hv/channel_mgmt.c | 188 +++++++++++++++++++++++++-------------
> drivers/hv/connection.c | 24 ++++-
> drivers/hv/hyperv_vmbus.h | 7 ++
> include/linux/hyperv.h | 7 ++
> 4 files changed, 161 insertions(+), 65 deletions(-)
As Sasha pointed out, this patch does not even apply :(
next prev parent reply other threads:[~2018-11-26 19:35 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-26 2:28 [PATCH 0/2] Drivers: hv: vmbus: Miscellaneous fixes kys
2018-11-26 2:29 ` [PATCH 1/2] Drivers: hv: vmbus: check the creation_status in vmbus_establish_gpadl() kys
2018-11-26 2:29 ` [PATCH 2/2] Drivers: hv: vmbus: offload the handling of channels to two workqueues kys
2018-11-26 5:23 ` Sasha Levin
2018-11-26 19:35 ` Greg KH [this message]
2018-11-26 21:12 ` Dexuan Cui
2018-11-27 5:22 ` KY Srinivasan
[not found] ` <20181126095254.824D420672@mail.kernel.org>
2018-11-26 21:02 ` [PATCH 1/2] Drivers: hv: vmbus: check the creation_status in vmbus_establish_gpadl() Dexuan Cui
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