linux-kernel - Re: [RFT/RFC] power_supply: bq2415x_charger: Initialize workqueue before scheduling it

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Date:	Mon, 27 Jul 2015 16:48:00 +0200
From:	Pali Rohár <pali.rohar@...il.com>
To:	Sebastian Reichel <sre@...nel.org>
Cc:	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>,
	David Woodhouse <dwmw2@...radead.org>,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFT/RFC] power_supply: bq2415x_charger: Initialize workqueue
 before scheduling it

On Monday 27 July 2015 16:22:29 Sebastian Reichel wrote:
> Hi,
> 
> On Sat, Jul 25, 2015 at 11:49:06PM +0200, Pali Rohár wrote:
> > On Tuesday 14 July 2015 02:34:13 Krzysztof Kozlowski wrote:
> > > The driver during probe registers a power supply notifier
> > > (with bq2415x_notifier_call() callback) and calls it manually right
> > > after. The notifier callback function schedules driver's workqueue
> > > (bq->work).
> > > 
> > > However the workqueue was initialized after these two events (after
> > > registering power supply notifier and calling manually the callback).
> > > 
> > > When power supply core notified the driver (executing its
> > > bq2415x_notifier_call() callback) the scheduled workqueue could be
> > > still uninitialized.
> > > 
> > > Signed-off-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>
> > > Reported-by: Pali Rohár <pali.rohar@...il.com>
> > > 
> > > ---
> > > 
> > > I don't have the hardware, please test. Additionally I could not find
> > > the commit which introduced the issue so I did not cc-stable.
> > > ---
> > >  drivers/power/bq2415x_charger.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/power/bq2415x_charger.c
> > > b/drivers/power/bq2415x_charger.c index e98dcb661cc9..527ed0f18796
> > > 100644
> > > --- a/drivers/power/bq2415x_charger.c
> > > +++ b/drivers/power/bq2415x_charger.c
> > > @@ -1601,6 +1601,7 @@ static int bq2415x_probe(struct i2c_client
> > > *client, bq->reported_mode = BQ2415X_MODE_OFF;
> > >  	bq->autotimer = 0;
> > >  	bq->automode = 0;
> > > +	INIT_DELAYED_WORK(&bq->work, bq2415x_timer_work);
> > > 
> > >  	if (np || ACPI_HANDLE(bq->dev)) {
> > >  		ret = device_property_read_u32(bq->dev,
> > > @@ -1677,7 +1678,6 @@ static int bq2415x_probe(struct i2c_client
> > > *client, dev_info(bq->dev, "automode not supported\n");
> > >  	}
> > > 
> > > -	INIT_DELAYED_WORK(&bq->work, bq2415x_timer_work);
> > >  	bq2415x_set_autotimer(bq, 1);
> > > 
> > >  	dev_info(bq->dev, "driver registered\n");
> > 
> > Looks like this is really problem. I sent alternative patch to mailing 
> > list which should fix this problem too plus allows to load 
> > bq2415x_charger.ko in n900 qemu.
> 
> I have not yet reviewed your patch (just skipped over it), but the
> qemu changes are a bit intrusive for -rc. I suggest to apply this
> patch for 4.2-rc. The extended patch can then be added in 4.3.
> 
> -- Sebastian

I'm not sure if this patch is enough... as timer_work should be called
after that init bq2415x_set_autotimer call.

I'm ok with postponing my patch later for 4.3. So if you think apply
this one for 4.2...

-- 
Pali Rohár
pali.rohar@...il.com
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