From acd36a42487038074d82b86413c09ac6aa0993ea Mon Sep 17 00:00:00 2001
From: Vitaly Kuznetsov <vkuznets@redhat.com>
Date: Fri, 26 Feb 2016 15:13:16 -0800
Subject: [PATCH 34/44] Drivers: hv: vmbus: avoid wait_for_completion() on
 crash
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wait_for_completion() may sleep, it enables interrupts and this
is something we really want to avoid on crashes because interrupt
handlers can cause other crashes. Switch to the recently introduced
vmbus_wait_for_unload() doing busy wait instead.

Reported-by: Radim Krcmar <rkrcmar@redhat.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Radim Kr.má<rkrcmar@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 75ff3a8a9168df750b5bd0589e897a6c0517a9f1)
---
 drivers/hv/channel_mgmt.c | 4 ++--
 drivers/hv/connection.c   | 2 +-
 drivers/hv/hyperv_vmbus.h | 2 +-
 drivers/hv/vmbus_drv.c    | 4 ++--
 4 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index b40f429aaa13..f70e35278b94 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -641,7 +641,7 @@ static void vmbus_unload_response(struct vmbus_channel_message_header *hdr)
 	complete(&vmbus_connection.unload_event);
 }
 
-void vmbus_initiate_unload(void)
+void vmbus_initiate_unload(bool crash)
 {
 	struct vmbus_channel_message_header hdr;
 
@@ -658,7 +658,7 @@ void vmbus_initiate_unload(void)
 	 * vmbus_initiate_unload() is also called on crash and the crash can be
 	 * happening in an interrupt context, where scheduling is impossible.
 	 */
-	if (!in_interrupt())
+	if (!crash)
 		wait_for_completion(&vmbus_connection.unload_event);
 	else
 		vmbus_wait_for_unload();
diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
index 4a1679d54c1f..46cc9c639775 100644
--- a/drivers/hv/connection.c
+++ b/drivers/hv/connection.c
@@ -233,7 +233,7 @@ void vmbus_disconnect(void)
 	/*
 	 * First send the unload request to the host.
 	 */
-	vmbus_initiate_unload();
+	vmbus_initiate_unload(false);
 
 	if (vmbus_connection.work_queue) {
 		drain_workqueue(vmbus_connection.work_queue);
diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index 9976774d6abc..4aadad6a0cde 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -756,7 +756,7 @@ void hv_vss_onchannelcallback(void *);
 int hv_fcopy_init(struct hv_util_service *);
 void hv_fcopy_deinit(void);
 void hv_fcopy_onchannelcallback(void *);
-void vmbus_initiate_unload(void);
+void vmbus_initiate_unload(bool crash);
 
 static inline void hv_poll_channel(struct vmbus_channel *channel,
 				   void (*cb)(void *))
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index a220efc297c4..d9801855ad4e 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -1276,7 +1276,7 @@ static void hv_kexec_handler(void)
 	int cpu;
 
 	hv_synic_clockevents_cleanup();
-	vmbus_initiate_unload();
+	vmbus_initiate_unload(false);
 	for_each_online_cpu(cpu)
 		smp_call_function_single(cpu, hv_synic_cleanup, NULL, 1);
 	hv_cleanup(false);
@@ -1284,7 +1284,7 @@ static void hv_kexec_handler(void)
 
 static void hv_crash_handler(struct pt_regs *regs)
 {
-	vmbus_initiate_unload();
+	vmbus_initiate_unload(true);
 	/*
 	 * In crash handler we can't schedule synic cleanup for all CPUs,
 	 * doing the cleanup for current CPU only. This should be sufficient
-- 
2.13.0

