linux-kernel - Re: [PATCH] clockevents: Leave broadcast device shtudown only if the current device is always running.

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Message-ID: <alpine.LFD.2.02.1204111208070.2542@ionos>
Date:	Wed, 11 Apr 2012 12:10:59 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Feng Tang <feng.tang@...el.com>
cc:	suresh.b.siddha@...el.com, santosh.shilimkar@...com,
	linux-kernel@...r.kernel.org, johnstul@...ibm.com
Subject: Re: [PATCH] clockevents: Leave broadcast device shtudown only if
 the current device is always running.

On Wed, 11 Apr 2012, Feng Tang wrote:
> > Problem you encountered is not related to leaving the broadcast device
> > in shutdown mode. Problem is that we didn't track the mode change to
> > oneshot and later during idle entry/exit, when we request the broadcast
> > device services using CLOCK_EVT_NOTIFY_BROADCAST_ENTER etc,
> > tick_broadcast_oneshot_control() returns with out doing much as it
> > thinks broadcast device is in periodic mode.
> 
> Just curious, IIUC, the tick_broadcast_switch_to_oneshot() is only called
> during CPU init process in boot time or bring a offlined cpu back on. Why
> is it related to the deep idle?

Because a deep idle state might require the broadcast device and w/o
Suresh's patch it can't use it because it's in the wrong state.

Thanks,

	tglx
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