linux-kernel - Re: [linux-pm] [PATCH 0/9] x86 idle cruft removal

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Message-ID: <4D959D25.5010805@linux.vnet.ibm.com>
Date:	Fri, 01 Apr 2011 15:08:45 +0530
From:	Trinabh Gupta <trinabh@...ux.vnet.ibm.com>
To:	Len Brown <lenb@...nel.org>
CC:	x86@...nel.org, linux-pm@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [linux-pm] [PATCH 0/9] x86 idle cruft removal - v2

> 2.6.39-rc1
> ----------
>
> x86 idle: deprecate floppy disable_hlt
> 	feature-removal.txt for 2.6.40 (4 months)
> 	WARN_ONCE on use
> 	cc: stable@...nel.org
>
> x86 idle APM: deprecate apm_cpu_idle
> 	feature-removal.txt for 2.6.40 (4 months)
> 	#warning on CONFIG_APM_CPU_IDLE remove in 2.6.40
> 	WARN_ONCE in apm_cpu_idle()
> 	cc: stable@...nel.org
>
> x86 idle: export pm_idle only for CONFIG_APM_MODULE
> 	like we do for default_idle(),
> 	EXPORT_SYMBOL(pm_idle) only on CONFIG_APM_MODULE
>
> x86 idle: deprecate "no-hlt" cmdline param
> 	feature-removal.txt for 2.6.40 (4 months)
> 	cc stable@...nel.org
> 	WARN_ONCE if used, ask if idle=poll is sufficient
> 	same as idle=poll, except no-hlt also disables
> 		HLT in machine_halt().
>
> x86 idle: deprecate "idle=mwait"
> 	feature-removal.txt for 2.6.40 (4 months)
> 	cc stable@...nel.org
> 	WARN_ONCE on invocation
>
> x86 idle: re-name ce1_idle
> 	rename for clarity, no functional change
>
> 2.6.40-merge
> ------
> x86 idle: move mwait_idle_with_hints()
> 	out of process.c to cstate.c, make static
>
> x86 idle floppy: remove deprecated disable_hlt/enable_hlt
>
> x86 idle: delete deprecated idle=mwait
> 	default_idle() can use HLT
>
> cpuidle: add cmdline "cpuidle=off"
> 	allow falling back to native default_idle
>
> x86 idle xen: stop touching pm_idle and default_idle
> 	Xen Dom0 kernel only needs HLT, but include
> 	CPU_IDLE, ACPI etc for running on bare hardware.
> 	So when running in Xen Dom0 mode, disable cpuidle
> 	to fall back to default_idle.
>
> x86 idle APM: remove deprecated apm_cpu_idle()
> 	and its use of pm_idle
>
> x86 idle cpuidle: delete public use of pm_idle
> 	make pm_idle and default_idle static to process.c

Hi Len,

I guess this would eliminate the problems caused by pm_idle.
In that case I also think we need not implement a default
driver (like the one I had done https://lkml.org/lkml/2011/3/22/154)
to handle the case when acpi_idle and intel_idle may not register.

Additionally, we may not need to support multiple cpuidle driver 
registration as now there would be only acpi_idle and intel_idle
and mechanism already exists to select between the two.

Thanks,
-Trinabh

> 	add return value from cpu_idle_call()
> 	invoke cpu_idle_call from cpu_idle() rather than via pm_idle
>
> 	cpu_idle() {
> 		...
> 		if (cpu_idle_call())
> 			pm_idle();	/* non cpuidle default */
> 	}
>
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