linux-kernel - Re: [v8 PATCH 1/8]: cpuidle: cleanup drivers/cpuidle/cpuidle.c

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Message-ID: <20091014062412.GB8605@linux.vnet.ibm.com>
Date:	Wed, 14 Oct 2009 11:54:12 +0530
From:	Arun R Bharadwaj <arun@...ux.vnet.ibm.com>
To:	Balbir Singh <balbir@...ux.vnet.ibm.com>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Ingo Molnar <mingo@...e.hu>,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
	Dipankar Sarma <dipankar@...ibm.com>,
	Arjan van de Ven <arjan@...radead.org>,
	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	linux-arch@...r.kernel.org, linux-acpi@...r.kernel.org,
	Arun Bharadwaj <arun@...ux.vnet.ibm.com>
Subject: Re: [v8 PATCH 1/8]: cpuidle: cleanup drivers/cpuidle/cpuidle.c

* Balbir Singh <balbir@...ux.vnet.ibm.com> [2009-10-12 17:06:02]:

> * Arun R B <arun@...ux.vnet.ibm.com> [2009-10-08 15:19:42]:
> 
> > * Arun R Bharadwaj <arun@...ux.vnet.ibm.com> [2009-10-08 15:18:28]:
> > 
> > This patch cleans up drivers/cpuidle/cpuidle.c
> > Earlier cpuidle assumed pm_idle as the default idle loop. Break that
> > assumption and make it more generic. cpuidle_idle_call() which is the
> > main idle loop of cpuidle is to be called by architectures which have
> > registered to cpuidle.
> > 
> > Remove routines cpuidle_install/uninstall_idle_handler() which are not
> > needed anymore.
> > 
> >
> 
> [snip]
> 
>   /**
> > - * cpuidle_install_idle_handler - installs the cpuidle idle loop handler
> > - */
> > -void cpuidle_install_idle_handler(void)
> > -{
> > -	if (enabled_devices && (pm_idle != cpuidle_idle_call)) {
> > -		/* Make sure all changes finished before we switch to new idle */
> > -		smp_wmb();
> > -		pm_idle = cpuidle_idle_call;
> > -	}
> > -}
> > -
> > -/**
> > - * cpuidle_uninstall_idle_handler - uninstalls the cpuidle idle loop handler
> > - */
> > -void cpuidle_uninstall_idle_handler(void)
> > -{
> > -	if (enabled_devices && pm_idle_old && (pm_idle != pm_idle_old)) {
> > -		pm_idle = pm_idle_old;
> > -		cpuidle_kick_cpus();
> > -	}
> > -}
> > -
> 
> I see the routines above being called in from
> cpuidle_pause/resume_and_lock/unlock below and they are entries from
> ACPI on ACPI_PROCESSOR_NOTIFY_POWER and from the hotplug path, could
> you test them to make sure they are not broken. We also seem to be
> missing a cpuidle_kick_cpus() in cpuidle_pause_and_lock()
> 
> [snip]
> 

Hi Balbir,

yes, we definitely need a cpuidle_kick_cpus() in
cpuidle_pause_and_lock() since this is used while disabling the
cpuidle_device and the cpus need to be kicked out of the idle states.
I will test this modified code and see if it breaks hotplug.

thanks,
arun

> -- 
> 	Balbir
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