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Subject[PATCH v5 8/9] Drivers: hv: vmbus: Suspend after cleaning up hv_sock and sub channels
Date
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 <decui@microsoft.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
---
drivers/hv/channel_mgmt.c | 26 ++++++++++++++++++++++++++
drivers/hv/connection.c | 3 +++
drivers/hv/hyperv_vmbus.h | 12 ++++++++++++
drivers/hv/vmbus_drv.c | 44 +++++++++++++++++++++++++++++++++++++++++++-
4 files changed, 84 insertions(+), 1 deletion(-)

diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index 44b92fa..5518d03 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -545,6 +545,10 @@ 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.
@@ -944,6 +948,16 @@ 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.
*
@@ -954,6 +968,7 @@ 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;

@@ -993,6 +1008,8 @@ 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.
@@ -1018,6 +1035,10 @@ 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;
}
/*
@@ -1050,6 +1071,11 @@ 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();
}

void vmbus_hvsock_device_unregister(struct vmbus_channel *channel)
diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
index 806319c..99851ea 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 e657197..974b747 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -260,6 +260,18 @@ 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 45b976e..32ec951 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 +2147,44 @@ 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.
+ *
+ * Note: the counter nr_chan_close_on_suspend may never go above 0 if
+ * the VM has no sub-channel and hv_sock channel, e.g. a 1-vCPU VM.
+ */
+ if (atomic_read(&vmbus_connection.nr_chan_close_on_suspend) > 0)
+ 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 +2225,9 @@ 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
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