From: Dexuan Cui <de...@microsoft.com> Sent: Monday, August 19, 2019 6:52 PM
>
> Before suspend, Linux must make sure all the hv_sock channels have been
> properly cleaned up, because a hv_sock connection can not persist across
> hibernation, and the user-space app must be properly notified of the
> state change of the connection.
>
> Before suspend, Linux also must make sure all the sub-channels have been
> destroyed, i.e. the related channel structs of the sub-channels must be
> properly removed, otherwise they would cause a conflict when the
> sub-channels are recreated upon resume.
>
> Add a counter to track such channels, and vmbus_bus_suspend() should wait
> for the counter to drop to zero.
>
> Signed-off-by: Dexuan Cui <de...@microsoft.com>
> ---
> drivers/hv/channel_mgmt.c | 28 ++++++++++++++++++++++++++++
> drivers/hv/connection.c | 3 +++
> drivers/hv/hyperv_vmbus.h | 12 ++++++++++++
> drivers/hv/vmbus_drv.c | 41 ++++++++++++++++++++++++++++++++++++++++-
> 4 files changed, 83 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
> index f7a1184..8491d1b 100644
> --- a/drivers/hv/channel_mgmt.c
> +++ b/drivers/hv/channel_mgmt.c
> @@ -499,6 +499,8 @@ static void vmbus_add_channel_work(struct work_struct
> *work)
> return;
>
> err_deq_chan:
> + WARN_ON_ONCE(1);
> +
Why this change? I was thinking maybe it's a debug statement that got
left in.
> mutex_lock(&vmbus_connection.channel_mutex);
>
> /*
> @@ -545,6 +547,10 @@ static void vmbus_process_offer(struct vmbus_channel
> *newchannel)
>
> mutex_lock(&vmbus_connection.channel_mutex);
>
> + /* Remember the channels that should be cleaned up upon suspend. */
> + if (is_hvsock_channel(newchannel) || is_sub_channel(newchannel))
> + atomic_inc(&vmbus_connection.nr_chan_close_on_suspend);
> +
> /*
> * Now that we have acquired the channel_mutex,
> * we can release the potentially racing rescind thread.
> @@ -915,6 +921,16 @@ static void vmbus_onoffer(struct
> vmbus_channel_message_header *hdr)
> vmbus_process_offer(newchannel);
> }
>
> +static void check_ready_for_suspend_event(void)
> +{
> + /*
> + * If all the sub-channels or hv_sock channels have been cleaned up,
> + * then it's safe to suspend.
> + */
> + if (atomic_dec_and_test(&vmbus_connection.nr_chan_close_on_suspend))
> + complete(&vmbus_connection.ready_for_suspend_event);
> +}
> +
> /*
> * vmbus_onoffer_rescind - Rescind offer handler.
> *
> @@ -925,6 +941,7 @@ static void vmbus_onoffer_rescind(struct
> vmbus_channel_message_header *hdr)
> struct vmbus_channel_rescind_offer *rescind;
> struct vmbus_channel *channel;
> struct device *dev;
> + bool clean_up_chan_for_suspend;
>
> rescind = (struct vmbus_channel_rescind_offer *)hdr;
>
> @@ -964,6 +981,8 @@ static void vmbus_onoffer_rescind(struct
> vmbus_channel_message_header *hdr)
> return;
> }
>
> + clean_up_chan_for_suspend = is_hvsock_channel(channel) ||
> + is_sub_channel(channel);
> /*
> * Before setting channel->rescind in vmbus_rescind_cleanup(), we
> * should make sure the channel callback is not running any more.
> @@ -989,6 +1008,10 @@ static void vmbus_onoffer_rescind(struct
> vmbus_channel_message_header *hdr)
> if (channel->device_obj) {
> if (channel->chn_rescind_callback) {
> channel->chn_rescind_callback(channel);
> +
> + if (clean_up_chan_for_suspend)
> + check_ready_for_suspend_event();
> +
> return;
> }
> /*
> @@ -1021,6 +1044,11 @@ static void vmbus_onoffer_rescind(struct
> vmbus_channel_message_header *hdr)
> }
> mutex_unlock(&vmbus_connection.channel_mutex);
> }
> +
> + /* The "channel" may have been freed. Do not access it any longer. */
> +
> + if (clean_up_chan_for_suspend)
> + check_ready_for_suspend_event();
> }
Having to add the above lines twice is a bit clumsy, but the problem is
the overall structure of the vmbus_onoffer_rescind. The early return in
the case of a rescind_callback function is a bit weird, but I guess it makes
sense since from what I can tell, only uio and hv_sock have rescind callback
functions. Some minor restructuring might be warranted, but I don't feel
strongly about it.
>
> void vmbus_hvsock_device_unregister(struct vmbus_channel *channel)
> diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
> index 701d9a8..f15d3115 100644
> --- a/drivers/hv/connection.c
> +++ b/drivers/hv/connection.c
> @@ -26,6 +26,9 @@
> struct vmbus_connection vmbus_connection = {
> .conn_state = DISCONNECTED,
> .next_gpadl_handle = ATOMIC_INIT(0xE1E10),
> +
> + .ready_for_suspend_event= COMPLETION_INITIALIZER(
> + vmbus_connection.ready_for_suspend_event),
> };
> EXPORT_SYMBOL_GPL(vmbus_connection);
>
> diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
> index 4610277..9f96e23 100644
> --- a/drivers/hv/hyperv_vmbus.h
> +++ b/drivers/hv/hyperv_vmbus.h
> @@ -258,6 +258,18 @@ struct vmbus_connection {
> struct workqueue_struct *work_queue;
> struct workqueue_struct *handle_primary_chan_wq;
> struct workqueue_struct *handle_sub_chan_wq;
> +
> + /*
> + * The number of sub-channels and hv_sock channels that should be
> + * cleaned up upon suspend: sub-channels will be re-created upon
> + * resume, and hv_sock channels should not survive suspend.
> + */
> + atomic_t nr_chan_close_on_suspend;
> + /*
> + * vmbus_bus_suspend() waits for "nr_chan_close_on_suspend" to
> + * drop to zero.
> + */
> + struct completion ready_for_suspend_event;
> };
>
>
> diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
> index 2bea669..0507157 100644
> --- a/drivers/hv/vmbus_drv.c
> +++ b/drivers/hv/vmbus_drv.c
> @@ -2127,7 +2127,8 @@ static int vmbus_acpi_add(struct acpi_device *device)
>
> static int vmbus_bus_suspend(struct device *dev)
> {
> - struct vmbus_channel *channel;
> + struct vmbus_channel *channel, *sc;
> + unsigned long flags;
>
> while (atomic_read(&vmbus_connection.offer_in_progress) != 0) {
> /*
> @@ -2146,6 +2147,41 @@ static int vmbus_bus_suspend(struct device *dev)
> }
> mutex_unlock(&vmbus_connection.channel_mutex);
>
> + /*
> + * Wait until all the sub-channels and hv_sock channels have been
> + * cleaned up. Sub-channels should be destroyed upon suspend, otherwise
> + * they would conflict with the new sub-channels that will be created
> + * in the resume path. hv_sock channels should also be destroyed, but
> + * a hv_sock channel of an established hv_sock connection can not be
> + * really destroyed since it may still be referenced by the userspace
> + * application, so we just force the hv_sock channel to be rescinded
> + * by vmbus_force_channel_rescinded(), and the userspace application
> + * will thoroughly destroy the channel after hibernation.
> + */
> + if (atomic_read(&vmbus_connection.nr_chan_close_on_suspend) > 0)
At first glance, the above line seemed useless to me. You could just do the
wait_for_completion() unconditionally. But is the intent to handle the case
where
the VM never had any sub-channels or hv_sock channels, and so
nr_chan_close_on_suspend never went above 0? If so, a comment might
be helpful.
> + wait_for_completion(&vmbus_connection.ready_for_suspend_event);
> +
> + mutex_lock(&vmbus_connection.channel_mutex);
> +
> + list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {
> + if (is_hvsock_channel(channel)) {
> + if (!channel->rescind) {
> + pr_err("hv_sock channel not rescinded!\n");
> + WARN_ON_ONCE(1);
> + }
> + continue;
> + }
> +
> + spin_lock_irqsave(&channel->lock, flags);
> + list_for_each_entry(sc, &channel->sc_list, sc_list) {
> + pr_err("Sub-channel not deleted!\n");
> + WARN_ON_ONCE(1);
> + }
> + spin_unlock_irqrestore(&channel->lock, flags);
> + }
> +
> + mutex_unlock(&vmbus_connection.channel_mutex);
> +
> vmbus_initiate_unload(false);
>
> vmbus_connection.conn_state = DISCONNECTED;
> @@ -2186,6 +2222,9 @@ static int vmbus_bus_resume(struct device *dev)
>
> vmbus_request_offers();
>
> + /* Reset the event for the next suspend. */
> + reinit_completion(&vmbus_connection.ready_for_suspend_event);
> +
> return 0;
> }
>
> --
> 1.8.3.1
