From d1d1e90f2106c7048feab6a6da955fc2ed521896 Mon Sep 17 00:00:00 2001
From: Dexuan Cui <decui@microsoft.com>
Date: Fri, 5 May 2017 16:57:15 -0600
Subject: [PATCH 3/9] vmbus: add the matching tasklet_enable() in
 vmbus_close_internal()

If we disable a tasklet that is scheduled but hasn't started to run,
the tasklet has no chance to run any longer, so later we'll hang
in free_channel() -> tasklet_kill(), because the TASKLET_STATE_SCHED
can't be cleared in tasklet_action().

With the patch, before free_channel() -> tasklet_kill() returns, the
tasklet still has a chance to run with a NULL channel->onchannel_callback,
which will be ignored safely, e.g. by vmbus_on_event().

Fixes: dad72a1d2844 ("vmbus: remove hv_event_tasklet_disable/enable")

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>
Origin: https://github.com/dcui/linux/commits/decui/hv_sock/v4.11/20170511
(cherry picked from commit 008d8d8bc0c86473a8549a365bee9a479243e412)
---
 drivers/hv/channel.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
index 628d6fde1887..7cd2bd9fd1f1 100644
--- a/drivers/hv/channel.c
+++ b/drivers/hv/channel.c
@@ -608,6 +608,7 @@ static int vmbus_close_internal(struct vmbus_channel *channel)
 		get_order(channel->ringbuffer_pagecount * PAGE_SIZE));
 
 out:
+	tasklet_enable(&channel->callback_event);
 	return ret;
 }
 
-- 
2.12.2

