linux-kernel - Re: [patch -resend] leds-lp5523: BUG() in error handling in probe()

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Message-ID: <20120627105547.GD3007@mwanda>
Date:	Wed, 27 Jun 2012 13:55:47 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	Bryan Wu <bryan.wu@...onical.com>
Cc:	Richard Purdie <rpurdie@...ys.net>, linux-leds@...r.kernel.org,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
	Matt Renzelmann <mjr@...wisc.edu>
Subject: Re: [patch -resend] leds-lp5523: BUG() in error handling in probe()

On Wed, Jun 27, 2012 at 06:49:10PM +0800, Bryan Wu wrote:
> On Wed, Jun 27, 2012 at 5:10 PM, Dan Carpenter <dan.carpenter@...cle.com> wrote:
> > Inside the error handling in lp5523_init_led(), there is a place that
> > calls to led_classdev_unregister().  When we unregister the LED drivers,
> > it tries to set the brightness to OFF.  In this driver setting the
> > brightness is done through a work queue and the work queue hasn't been
> > initialized yet.
> >
> > The result is that we trigger a WARN_ON() in the __queue_work().
> >
> > The fix is to move the INIT_WORK() in front of the call to
> > lp5523_init_led().
> >
> 
> Thanks for resending this, I applied this in my for-next branch.
> 
> > Matt Renzelmann found this using a bug finding tool.
> 
> Just be curious, what's kind of the tool here?
> 

Sorry I should have CC'd Matt on this.  I think it's something he
is working on at the University of Wisconsin.  That's all I know.

regards,
dan carpenter

> -Bryan
> 
> >
> > Reported-by: Matt Renzelmann <mjr@...wisc.edu>
> > Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
> > ---
> > I don't have this hardware, so I can't test it.  I originally sent this
> > on Fri, 13 Apr 2012, and that was before Bryan Wu took on the LED
> > subsystem.  Also when I sent it, the WARN_ON() in __queue_work() was
> > a BUG_ON() so I've updated the commit message.
> >
> > diff --git a/drivers/leds/leds-lp5523.c b/drivers/leds/leds-lp5523.c
> > index 857a3e1..e8a2712 100644
> > --- a/drivers/leds/leds-lp5523.c
> > +++ b/drivers/leds/leds-lp5523.c
> > @@ -943,6 +943,9 @@ static int __devinit lp5523_probe(struct i2c_client *client,
> >                if (pdata->led_config[i].led_current == 0)
> >                        continue;
> >
> > +               INIT_WORK(&chip->leds[led].brightness_work,
> > +                       lp5523_led_brightness_work);
> > +
> >                ret = lp5523_init_led(&chip->leds[led], &client->dev, i, pdata);
> >                if (ret) {
> >                        dev_err(&client->dev, "error initializing leds\n");
> > @@ -956,9 +959,6 @@ static int __devinit lp5523_probe(struct i2c_client *client,
> >                          LP5523_REG_LED_CURRENT_BASE + chip->leds[led].chan_nr,
> >                          chip->leds[led].led_current);
> >
> > -               INIT_WORK(&(chip->leds[led].brightness_work),
> > -                       lp5523_led_brightness_work);
> > -
> >                led++;
> >        }
> >
> 
> 
> 
> -- 
> Bryan Wu <bryan.wu@...onical.com>
> Kernel Developer    +86.186-168-78255 Mobile
> Canonical Ltd.      www.canonical.com
> Ubuntu - Linux for human beings | www.ubuntu.com
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