x86: disable TSC for sched_clock() when calibration failed

upstream commit: 74dc51a3de06aa516e3b9fdc4017b2aeb38bf44b

When the TSC calibration fails then TSC is still used in
sched_clock(). Disable it completely in that case.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@kernel.org
Signed-off-by: Chris Wright <chrisw@sous-sol.org>

diff --git a/arch/x86/kernel/tsc_32.c b/arch/x86/kernel/tsc_32.c
index 021723ccd50750d8788bb085e683fdc472394679..01e4f8b2624c5b840d87c78c7ed02f45eb155681 100644 (file)
--- a/arch/x86/kernel/tsc_32.c
+++ b/arch/x86/kernel/tsc_32.c
@@ -401,6 +401,11 @@ void __init tsc_init(void)
 
        if (!cpu_khz) {
                mark_tsc_unstable("could not calculate TSC khz");
+               /*
+                * We need to disable the TSC completely in this case
+                * to prevent sched_clock() from using it.
+                */
+               tsc_disabled = 1;
                return;
        }