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    SubjectRe: + restore-missing-sysfs-max_cstate-attr.patch added to -mm tree
    On Sun, 06 Jan 2008 16:34:16 -0500 Mark Lord <lkml@rtr.ca> wrote:

    > Venki Pallipadi wrote:
    > > Reintroduce run time configurable max_cstate for !CPU_IDLE case.
    > >
    > > Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
    > >
    > > Index: linux-2.6.24-rc/drivers/acpi/processor_idle.c
    > > ===================================================================
    > > --- linux-2.6.24-rc.orig/drivers/acpi/processor_idle.c
    > > +++ linux-2.6.24-rc/drivers/acpi/processor_idle.c
    > > @@ -76,7 +76,11 @@ static void (*pm_idle_save) (void) __rea
    > > #define PM_TIMER_TICKS_TO_US(p) (((p) * 1000)/(PM_TIMER_FREQUENCY/1000))
    > >
    > > static unsigned int max_cstate __read_mostly = ACPI_PROCESSOR_MAX_POWER;
    > > +#ifdef CONFIG_CPU_IDLE
    > > module_param(max_cstate, uint, 0000);
    > > +#else
    > > +module_param(max_cstate, uint, 0644);
    > > +#endif
    > > static unsigned int nocst __read_mostly;
    > > module_param(nocst, uint, 0000);
    > >
    > ..
    >
    > Can we get this patch upstream so that a stock 2.6.24 will work here?
    >

    umm, OK, I queued it for 2.6.24. I'll give people a day or so to comment
    on this.

    I had to invent some silly changlelog for it. Please review it for
    accuracy and completeness?

    It isn't complete, really. How come we only make max_cstate writeable if
    CONFIG_CPU_IDLE=n? What happens to people who were reliant upon writeable
    max_cstate who now enable CPU_IDLE? Things still break? What is the
    rationale behind this? What constraints led us to this decision?




    From: Venki Pallipadi <venkatesh.pallipadi@intel.com>

    This was writeable in 2.6.23 but the cpuidle merge made it read-only. But
    some people's scripts (ie: Mark's) were writing to it.

    As an unhappy compromise, make max_cstate writeable again if the kernel was
    configured without CONFIG_CPU_IDLE.

    Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
    Cc: Mark Lord <lkml@rtr.ca>
    Cc: Arjan van de Ven <arjan@infradead.org>
    Cc: Len Brown <lenb@kernel.org>
    Cc: Ingo Molnar <mingo@elte.hu>
    Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    ---

    drivers/acpi/processor_idle.c | 4 ++++
    1 file changed, 4 insertions(+)

    diff -puN drivers/acpi/processor_idle.c~reintroduce-run-time-configurable-max_cstate-for-cpu_idle-case drivers/acpi/processor_idle.c
    --- a/drivers/acpi/processor_idle.c~reintroduce-run-time-configurable-max_cstate-for-cpu_idle-case
    +++ a/drivers/acpi/processor_idle.c
    @@ -76,7 +76,11 @@ static void (*pm_idle_save) (void) __rea
    #define PM_TIMER_TICKS_TO_US(p) (((p) * 1000)/(PM_TIMER_FREQUENCY/1000))

    static unsigned int max_cstate __read_mostly = ACPI_PROCESSOR_MAX_POWER;
    +#ifdef CONFIG_CPU_IDLE
    module_param(max_cstate, uint, 0000);
    +#else
    +module_param(max_cstate, uint, 0644);
    +#endif
    static unsigned int nocst __read_mostly;
    module_param(nocst, uint, 0000);

    _


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