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Subject[patch 28/50] x86: disable TSC for sched_clock() when calibration failed
-stable review patch.  If anyone has any objections, please let us know.
---------------------
From: Thomas Gleixner <tglx@linutronix.de>

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>
---
arch/x86/kernel/tsc_32.c | 5 +++++
1 file changed, 5 insertions(+)
--- 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;
}

--


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