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

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Date:	Mon, 27 Jul 2015 16:22:29 +0200
From:	Sebastian Reichel <sre@...nel.org>
To:	Pali Rohár <pali.rohar@...il.com>
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

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

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