linux-kernel - Re: [PATCH 3/3] pcf50633_charger: Enable periodic charging restart

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Message-ID: <20090203003345.GB29462@zarina>
Date:	Tue, 3 Feb 2009 03:33:45 +0300
From:	Anton Vorontsov <cbouatmailru@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Balaji Rao <balajirrao@...nmoko.org>, linux-kernel@...r.kernel.org,
	cbou@...l.ru, andy@...nmoko.com
Subject: Re: [PATCH 3/3] pcf50633_charger: Enable periodic charging restart

On Mon, Feb 02, 2009 at 02:41:31PM -0800, Andrew Morton wrote:
> On Tue, 27 Jan 2009 19:23:12 +0530
> Balaji Rao <balajirrao@...nmoko.org> wrote:
> 
> > @@ -157,6 +213,7 @@ pcf50633_mbc_irq_handler(int irq, void *data)
> >  		mbc->usb_online = 0;
> >  		mbc->usb_active = 0;
> >  		pcf50633_mbc_usb_curlim_set(mbc->pcf, 0);
> > +		cancel_delayed_work_sync(&mbc->charging_restart_work);
> >  	}
> 
> eek, can't call cancel_delayed_work_sync() from an interrupt handler! 

It's rather confusing, but it's not an irq handler, in the sense that
it does not run in atomic context -- the PCF IRQ handlers run in
kernel threads.

It's done that way because PCF50633 is an I2C device, and normally
we can't access I2C devices in the atomic context (plus it's rather
slow, thus would cause huge latencies if we'd try).

-- 
Anton Vorontsov
email: cbouatmailru@...il.com
irc://irc.freenode.net/bd2
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