From: Zhenzhong Duan <zhenzhong.duan@oracle.com>
Date: Wed, 21 Jun 2017 08:23:37 +0000 (-0700)
Subject: x86/tsc: Call check_system_tsc_reliable() before unsynchronized_tsc()
X-Git-Tag: v4.13-rc1~188^2
X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=a1272dd5531b259bf7313ac7597a67362698038c;p=linux.git

x86/tsc: Call check_system_tsc_reliable() before unsynchronized_tsc()

tsc_clocksource_reliable is initialized in check_system_tsc_reliable(), but
it is checked in unsynchronized_tsc() which is called before the
initialization.

In practice that's not an issue because systems which mark the TSC
reliable have X86_FEATURE_CONSTANT_TSC set as well, which is evaluated
in unsynchronized_tsc() before tsc_clocksource_reliable.

Reorder the calls so initialization happens before usage.

[ tglx: Massaged changelog ]

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/b1532ef7-cd9f-45f7-9f49-48dd2a5c2495@default
---

diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 714dfba6a1e7..a316bdd42a37 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -1412,11 +1412,11 @@ void __init tsc_init(void)
 
 	use_tsc_delay();
 
+	check_system_tsc_reliable();
+
 	if (unsynchronized_tsc())
 		mark_tsc_unstable("TSCs unsynchronized");
 
-	check_system_tsc_reliable();
-
 	detect_art();
 }