[PATCH v2 1/7] x86,tsc: Always unregister clocksource_tsc_early

From: Peter Zijlstra
Date: Mon Apr 30 2018 - 06:06:06 EST


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@xxxxxxxxx>
Fixes: aa83c45762a2 ("x86/tsc: Introduce early tsc clocksource")
Cc: stable@xxxxxxxxxx
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
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
@@ -1244,7 +1244,7 @@ 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
@@ -1297,11 +1297,12 @@ 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);
}

@@ -1311,8 +1312,8 @@ 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;
@@ -1328,6 +1329,7 @@ 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;
}