linux-kernel - [PATCH 4.16 46/52] x86/tsc: Always unregister clocksource_tsc

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Date:   Tue,  8 May 2018 10:10:44 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        len.brown@...el.com, rjw@...ysocki.net, diego.viola@...il.com,
        rui.zhang@...el.com
Subject: [PATCH 4.16 46/52] x86/tsc: Always unregister clocksource_tsc_early

4.16-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Peter Zijlstra <peterz@...radead.org>

commit e9088adda13cd23249d4b0abb97ff8a81bf5573a upstream.

Don't leave the tsc-early clocksource registered if it errors out
early.

This was reported by Diego, who on his Core2 era machine got TSC
invalidated while it was running with tsc-early (due to C-states).
This results in keeping tsc-early with very bad effects.

Reported-and-Tested-by: Diego Viola <diego.viola@...il.com>
Fixes: aa83c45762a2 ("x86/tsc: Introduce early tsc clocksource")
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Cc: len.brown@...el.com
Cc: rjw@...ysocki.net
Cc: diego.viola@...il.com
Cc: rui.zhang@...el.com
Cc: stable@...r.kernel.org
Link: https://lkml.kernel.org/r/20180430100344.350507853@infradead.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/kernel/tsc.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -1205,7 +1205,7 @@ static void tsc_refine_calibration_work(

 	/* Don't bother refining TSC on unstable systems */
 	if (tsc_unstable)
-		return;
+		goto unreg;

 	/*
 	 * Since the work is started early in boot, we may be
@@ -1258,11 +1258,12 @@ static void tsc_refine_calibration_work(

 out:
 	if (tsc_unstable)
-		return;
+		goto unreg;

 	if (boot_cpu_has(X86_FEATURE_ART))
 		art_related_clocksource = &clocksource_tsc;
 	clocksource_register_khz(&clocksource_tsc, tsc_khz);
+unreg:
 	clocksource_unregister(&clocksource_tsc_early);
 }

@@ -1272,8 +1273,8 @@ static int __init init_tsc_clocksource(v
 	if (!boot_cpu_has(X86_FEATURE_TSC) || tsc_disabled > 0 || !tsc_khz)
 		return 0;

-	if (check_tsc_unstable())
-		return 0;
+	if (tsc_unstable)
+		goto unreg;

 	if (tsc_clocksource_reliable)
 		clocksource_tsc.flags &= ~CLOCK_SOURCE_MUST_VERIFY;
@@ -1289,6 +1290,7 @@ static int __init init_tsc_clocksource(v
 		if (boot_cpu_has(X86_FEATURE_ART))
 			art_related_clocksource = &clocksource_tsc;
 		clocksource_register_khz(&clocksource_tsc, tsc_khz);
+unreg:
 		clocksource_unregister(&clocksource_tsc_early);
 		return 0;
 	}