From: Vitaly Kuznetsov <vkuznets@redhat.com>
Date: Thu, 28 Jan 2016 06:29:36 +0000 (-0800)
Subject: Drivers: hv: vmbus: don't manipulate with clocksources on crash
X-Git-Tag: firefly_0821_release~176^2~4^2~31^2~98
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=bee629f1b07375d467a679797acbf8d8ab3db61f;p=firefly-linux-kernel-4.4.55.git

Drivers: hv: vmbus: don't manipulate with clocksources on crash

[ Upstream commit 3ccb4fd8f492f99aece21acc1bd6142275f26236 ]

clocksource_change_rating() involves mutex usage and can't be called
in interrupt context. It also makes sense to avoid doing redundant work
on crash.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index 6341be8739ae..63194a9a7189 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -293,8 +293,14 @@ void hv_cleanup(void)
 	 * Cleanup the TSC page based CS.
 	 */
 	if (ms_hyperv.features & HV_X64_MSR_REFERENCE_TSC_AVAILABLE) {
-		clocksource_change_rating(&hyperv_cs_tsc, 10);
-		clocksource_unregister(&hyperv_cs_tsc);
+		/*
+		 * Crash can happen in an interrupt context and unregistering
+		 * a clocksource is impossible and redundant in this case.
+		 */
+		if (!oops_in_progress) {
+			clocksource_change_rating(&hyperv_cs_tsc, 10);
+			clocksource_unregister(&hyperv_cs_tsc);
+		}
 
 		hypercall_msr.as_uint64 = 0;
 		wrmsrl(HV_X64_MSR_REFERENCE_TSC, hypercall_msr.as_uint64);