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Subject[patch 27/50] x86: distangle user disabled TSC from unstable
-stable review patch.  If anyone has any objections, please let us know.
---------------------
From: Thomas Gleixner <tglx@linutronix.de>

upstream commit: 9ccc906c97e34fd91dc6aaf5b69b52d824386910

tsc_enabled is set to 0 from the command line switch "notsc" and from
the mark_tsc_unstable code. Seperate those functionalities and replace
tsc_enable with tsc_disable. This makes also the native_sched_clock()
decision when to use TSC understandable.

Preparatory patch to solve the sched_clock() issue on 32 bit.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
---
arch/x86/kernel/tsc_32.c | 20 ++++++++++----------
1 file changed, 10 insertions(+), 10 deletions(-)
--- a/arch/x86/kernel/tsc_32.c
+++ b/arch/x86/kernel/tsc_32.c
@@ -14,7 +14,7 @@

#include "mach_timer.h"

-static int tsc_enabled;
+static int tsc_disabled;

/*
* On some systems the TSC frequency does not
@@ -28,8 +28,8 @@ EXPORT_SYMBOL_GPL(tsc_khz);
static int __init tsc_setup(char *str)
{
printk(KERN_WARNING "notsc: Kernel compiled with CONFIG_X86_TSC, "
- "cannot disable TSC completely.\n");
- mark_tsc_unstable("user disabled TSC");
+ "cannot disable TSC completely.\n");
+ tsc_disabled = 1;
return 1;
}
#else
@@ -121,7 +121,7 @@ unsigned long long native_sched_clock(vo
* very important for it to be as fast as the platform
* can achive it. )
*/
- if (unlikely(!tsc_enabled && !tsc_unstable))
+ if (unlikely(tsc_disabled))
/* No locking but a rare wrong value is not a big deal: */
return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ);

@@ -310,7 +310,6 @@ void mark_tsc_unstable(char *reason)
{
if (!tsc_unstable) {
tsc_unstable = 1;
- tsc_enabled = 0;
printk("Marking TSC unstable due to: %s.\n", reason);
/* Can be called before registration */
if (clocksource_tsc.mult)
@@ -324,7 +323,7 @@ EXPORT_SYMBOL_GPL(mark_tsc_unstable);
static int __init dmi_mark_tsc_unstable(const struct dmi_system_id *d)
{
printk(KERN_NOTICE "%s detected: marking TSC unstable.\n",
- d->ident);
+ d->ident);
tsc_unstable = 1;
return 0;
}
@@ -391,8 +390,11 @@ void __init tsc_init(void)
{
int cpu;

- if (!cpu_has_tsc)
+ if (!cpu_has_tsc || tsc_disabled) {
+ /* Disable the TSC in case of !cpu_has_tsc */
+ tsc_disabled = 1;
return;
+ }

cpu_khz = calculate_cpu_khz();
tsc_khz = cpu_khz;
@@ -429,8 +431,6 @@ void __init tsc_init(void)
if (check_tsc_unstable()) {
clocksource_tsc.rating = 0;
clocksource_tsc.flags &= ~CLOCK_SOURCE_IS_CONTINUOUS;
- } else
- tsc_enabled = 1;
-
+ }
clocksource_register(&clocksource_tsc);
}
--


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