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Subject[PATCH V2 1/4] vmbus: don't acquire the mutex in vmbus_hvsock_device_unregister()
Date
From: Dexuan Cui <decui@microsoft.com>

Due to commit 54a66265d675 ("Drivers: hv: vmbus: Fix rescind handling"),
we need this patch to resolve the below deadlock:

after we get the mutex in vmbus_hvsock_device_unregister() and call
vmbus_device_unregister() -> device_unregister() -> ... -> device_release()
-> vmbus_device_release(), we'll get a deadlock, because
vmbus_device_release() tries to get the same mutex.

Signed-off-by: Dexuan Cui <decui@microsoft.com>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
---
drivers/hv/channel_mgmt.c | 4 ----
1 file changed, 4 deletions(-)

diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index 968af173c4c1..624d815745e4 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -945,14 +945,10 @@ static void vmbus_onoffer_rescind(struct vmbus_channel_message_header *hdr)

void vmbus_hvsock_device_unregister(struct vmbus_channel *channel)
{
- mutex_lock(&vmbus_connection.channel_mutex);
-
BUG_ON(!is_hvsock_channel(channel));

channel->rescind = true;
vmbus_device_unregister(channel->device_obj);
-
- mutex_unlock(&vmbus_connection.channel_mutex);
}
EXPORT_SYMBOL_GPL(vmbus_hvsock_device_unregister);

--
2.14.1
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