linux-kernel - [tip:x86/timers] x86/tsc: Call check_system_tsc_reliable() before unsynchronized

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Message-ID: <tip-a1272dd5531b259bf7313ac7597a67362698038c@git.kernel.org>
Date:   Thu, 22 Jun 2017 07:03:51 -0700
From:   tip-bot for Zhenzhong Duan <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     tglx@...utronix.de, hpa@...or.com, linux-kernel@...r.kernel.org,
        mingo@...nel.org, zhenzhong.duan@...cle.com
Subject: [tip:x86/timers] x86/tsc: Call check_system_tsc_reliable() before
 unsynchronized_tsc()

Commit-ID:  a1272dd5531b259bf7313ac7597a67362698038c
Gitweb:     http://git.kernel.org/tip/a1272dd5531b259bf7313ac7597a67362698038c
Author:     Zhenzhong Duan <zhenzhong.duan@...cle.com>
AuthorDate: Wed, 21 Jun 2017 01:23:37 -0700
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Thu, 22 Jun 2017 16:00:03 +0200

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@...cle.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/b1532ef7-cd9f-45f7-9f49-48dd2a5c2495@default
---
 arch/x86/kernel/tsc.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 714dfba..a316bdd 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();
 }