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SubjectRe: [RFC V1] cpuidle: add idle routine registration and cleanup pm_idle pointer
  On 10/19/2010 11:36 AM, Trinabh Gupta wrote:
> The core of the kernel's idle routine on x86 presently depends on an
> exported pm_idle function pointer that is unmanaged and causing
> hazard to various subsystems when they save and restore it.
> The first problem is that this exported pointer can be modified/flipped
> by any subsystem. There is no tracking or notification mechanism.
> Secondly and more importantly, various subsystems save the value of
> this pointer, flip it and later restore to the saved value. There is
> no guarantee that the saved value is still valid. The problem has
> been discussed in [2,3] and Peter Zijlstra suggested removing pm_idle
> and implementing a list based registration [1].
> This patch is an initial RFC implementation for x86 architecture
> only. This framework can be generalised for other archs and also
> include the current cpuidle framework for managing multiple idle
> routines.
> Tests done with the patch:
> ------------------------
> 1. Build (on 2.6.36-rc7) and booted on x86 with C1E as deepest idle
> state and current_idle was selected to be mwait_idle.
> 2. Build (on 2.5.36-rc8) and booted on x86 (Nehalem) with ACPI C3 as
> deepest sleep state. The current_idle was selected to be
> cpuidle_idle_call which is the cpuidle subsystem that will further
> select idle routines from {C1,C2,C3}.
> Future implementation will try to eliminate this hirearchy and have
> a single registration and menu/idle cpuidle governor for selection
> of idle routine.

looks like you're duplicating the cpuidle subsystem

how about biting the bullet and just always and only use the cpuidle
subsystem for all idle on x86 ?

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