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    SubjectRe: 2.6.25 regression: powertop says 120K wakeups/sec
    Rafael J. Wysocki wrote:
    > On Friday, 28 of March 2008, Venki Pallipadi wrote:
    >> On Fri, Mar 28, 2008 at 03:09:22PM -0700, David Brownell wrote:
    >>> On Friday 28 March 2008, Pallipadi, Venkatesh wrote:
    >>>> You should have a dmesg line which looks like
    >>>> ACPI: CPU0 (power states: C1[C1] C2[C2]
    >>>> Do you see C2 in such line?
    >>> Yes:
    >>>
    >>> ACPI: CPU0 (power states: C1[C1] C2[C2])
    >>
    >> David,
    >>
    >> I think I figured out the bug...
    >>
    >> Can you try the below patch and confirm that it works (over upstream - ignore
    >> the earlier revert patch I sent to you).
    >>
    >> Thanks,
    >> Venki
    >>
    >> ----
    >>
    >>
    >> Patch to fix huge number of wakeups reported due to recent changes in
    >> processor_idle.c. The problem was that the entry_method determination was
    >> broken due to one of the recent commits (bc71bec91f987) causing
    >> C1 entry to not to go to halt. This should also fix the hang reported here.
    >> http://bugzilla.kernel.org/show_bug.cgi?id=10093
    >
    > Ah, thanks for figuring that out. As a regression fix, it should go upstream
    > ASAP, I think.
    ..

    Would this have any applicability to 2.6.24 as well?

    I have seen/reported a similar bug there many times in the past,
    with no resolution. There's even a bugzilla entry for it somewhere.
    ???


    >> Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
    >>
    >> ---
    >> drivers/acpi/processor_idle.c | 4 ++++
    >> 1 file changed, 4 insertions(+)
    >>
    >> Index: linux-2.6/drivers/acpi/processor_idle.c
    >> ===================================================================
    >> --- linux-2.6.orig/drivers/acpi/processor_idle.c 2008-03-28 15:31:13.000000000 -0700
    >> +++ linux-2.6/drivers/acpi/processor_idle.c 2008-03-28 15:40:50.000000000 -0700
    >> @@ -848,6 +848,7 @@ static int acpi_processor_get_power_info
    >> /* all processors need to support C1 */
    >> pr->power.states[ACPI_STATE_C1].type = ACPI_STATE_C1;
    >> pr->power.states[ACPI_STATE_C1].valid = 1;
    >> + pr->power.states[ACPI_STATE_C1].entry_method = ACPI_CSTATE_HALT;
    >> }
    >> /* the C0 state only exists as a filler in our array */
    >> pr->power.states[ACPI_STATE_C0].valid = 1;
    >> @@ -960,6 +961,9 @@ static int acpi_processor_get_power_info
    >> cx.address);
    >> }
    >>
    >> + if (cx.type == ACPI_STATE_C1) {
    >> + cx.valid = 1;
    >> + }
    >>
    >> obj = &(element->package.elements[2]);
    >> if (obj->type != ACPI_TYPE_INTEGER)
    >>
    >>
    > --
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