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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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