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    Subject[PATCH 06/18] x86 idle: deprecate mwait_idle() and "idle=mwait" cmdline param
    Date
    From: Len Brown <len.brown@intel.com>

    mwait_idle() is a C1-only idle loop intended to be more efficient
    than HLT on SMP hardware that supports it.

    But mwait_idle() has been replaced by the more general
    mwait_idle_with_hints(), which handles both C1 and deeper C-states.
    ACPI uses only mwait_idle_with_hints(), and never uses mwait_idle().

    Deprecate mwait_idle() and the "idle=mwait" cmdline param
    to simplify the x86 idle code.

    After this change, kernels configured with
    (!CONFIG_ACPI=n && !CONFIG_INTEL_IDLE=n) when run on hardware
    that support MWAIT will simply use HLT. If MWAIT is desired
    on those systems, cpuidle and the cpuidle drivers above
    will support it.

    cc: x86@kernel.org
    cc: stable@kernel.org
    Signed-off-by: Len Brown <len.brown@intel.com>
    ---
    Documentation/feature-removal-schedule.txt | 7 +++++++
    arch/x86/kernel/process.c | 1 +
    2 files changed, 8 insertions(+), 0 deletions(-)

    diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt
    index f587159..9ee4a2c 100644
    --- a/Documentation/feature-removal-schedule.txt
    +++ b/Documentation/feature-removal-schedule.txt
    @@ -35,6 +35,13 @@ Who: Len Brown <len.brown@intel.com>

    ----------------------------

    +What: x86 "idle=mwait" cmdline param
    +When: 2.6.40
    +Why: simplify x86 idle code
    +Who: Len Brown <len.brown@intel.com>
    +
    +----------------------------
    +
    What: PRISM54
    When: 2.6.34

    diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
    index 17b8771..1f64501 100644
    --- a/arch/x86/kernel/process.c
    +++ b/arch/x86/kernel/process.c
    @@ -645,6 +645,7 @@ static int __init idle_setup(char *str)
    boot_option_idle_override = IDLE_POLL;
    } else if (!strcmp(str, "mwait")) {
    boot_option_idle_override = IDLE_FORCE_MWAIT;
    + WARN_ONCE(1, "\idle=mwait\" will be removed in 2.6.40\"\n");
    } else if (!strcmp(str, "halt")) {
    /*
    * When the boot option of idle=halt is added, halt is
    --
    1.7.5.rc0


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