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    SubjectRe: [patch 1/2] x86: Add pm_play_dead funcptr to power-efficiently offline CPUs
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    On Fri, 2009-05-22 at 16:19 -0700, venkatesh.pallipadi@intel.com wrote:
    > plain text document attachment
    > (0001-x86-Add-pm_play_dead-funcptr-to-power-efficiently-o.patch)
    > Add a funcptr pm_play_dead (similar to pm_idle) that can take
    > the offline CPUs to the most power efficient idle state.
    >
    > This patch just adds the func pointer. The pointer will get initialized
    > by patch that follows.

    Since the pm_idle function pointer has given us so much grief, I don't
    think its wise to repeat that particular disaster.

    I'd much rather see a framework where idle functions can be registered,
    and selected from based on criteria such as wakeup latency as provided
    by the pm_qos stuff, and power saving.

    This framework should be shared between hotplug-idle and the regular
    idle routines. Hotplug would of course not care about things like wakeup
    latency and might therefore pick another idle routine.

    > Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
    > ---
    > arch/x86/include/asm/smp.h | 2 ++
    > arch/x86/kernel/smpboot.c | 7 ++++++-
    > 2 files changed, 8 insertions(+), 1 deletions(-)
    >
    > diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
    > index 19e0d88..0388b81 100644
    > --- a/arch/x86/include/asm/smp.h
    > +++ b/arch/x86/include/asm/smp.h
    > @@ -148,6 +148,8 @@ static inline int num_booting_cpus(void)
    > {
    > return cpumask_weight(cpu_callout_mask);
    > }
    > +
    > +extern void (*pm_play_dead)(void);
    > #endif /* CONFIG_SMP */
    >
    > extern unsigned disabled_cpus __cpuinitdata;
    > diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
    > index 58d24ef..4f8af6a 100644
    > --- a/arch/x86/kernel/smpboot.c
    > +++ b/arch/x86/kernel/smpboot.c
    > @@ -1195,6 +1195,8 @@ __init void prefill_possible_map(void)
    > nr_cpu_ids = possible;
    > }
    >
    > +void (*pm_play_dead)(void) = NULL;
    > +
    > #ifdef CONFIG_HOTPLUG_CPU
    >
    > static void remove_siblinginfo(int cpu)
    > @@ -1313,7 +1315,10 @@ void play_dead_common(void)
    > void native_play_dead(void)
    > {
    > play_dead_common();
    > - wbinvd_halt();
    > + if (pm_play_dead)
    > + pm_play_dead();
    > + else
    > + wbinvd_halt();
    > }
    >
    > #else /* ... !CONFIG_HOTPLUG_CPU */
    > --
    > 1.6.0.6
    >



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