[tip:timers/urgent] x86/tsc: Always unregister clocksource_tsc_early

[tip-bot for Peter Zijlstra]

Commit-ID:  e9088adda13cd23249d4b0abb97ff8a81bf5573a
Gitweb:     https://git.kernel.org/tip/e9088adda13cd23249d4b0abb97ff8a81bf5573a
Author:     Peter Zijlstra <pet...@infradead.org>
AuthorDate: Mon, 30 Apr 2018 12:00:09 +0200
Committer:  Thomas Gleixner <t...@linutronix.de>
CommitDate: Wed, 2 May 2018 16:10:40 +0200

x86/tsc: Always unregister clocksource_tsc_early

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.vi...@gmail.com>
Fixes: aa83c45762a2 ("x86/tsc: Introduce early tsc clocksource")
Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
Signed-off-by: Thomas Gleixner <t...@linutronix.de>
Reviewed-by: Rafael J. Wysocki <rafael.j.wyso...@intel.com>
Cc: len.br...@intel.com
Cc: r...@rjwysocki.net
Cc: diego.vi...@gmail.com
Cc: rui.zh...@intel.com
Cc: sta...@vger.kernel.org
Link: https://lkml.kernel.org/r/20180430100344.350507...@infradead.org

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

diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 91e6da48cbb6..23f36bc236ba 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -1244,7 +1244,7 @@ static void tsc_refine_calibration_work(struct 
work_struct *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
@@ -1297,11 +1297,12 @@ static void tsc_refine_calibration_work(struct 
work_struct *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);
 }
 
@@ -1311,8 +1312,8 @@ static int __init init_tsc_clocksource(void)
        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;
@@ -1328,6 +1329,7 @@ static int __init init_tsc_clocksource(void)
                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;
        }