[PATCH] [media] lmedm04: Do not unlock mutex if mutex_lock_interruptible failed

[PATCH] [media] lmedm04: Do not unlock mutex if mutex_lock_interruptible failed

[Alexey Khoroshilov]

There are a couple of places where mutex_unlock() is called even 
if mutex_lock_interruptible() failed. The patch fixes the issue.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
---
 drivers/media/dvb/dvb-usb/lmedm04.c |   12 +++++++-----
 1 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/media/dvb/dvb-usb/lmedm04.c b/drivers/media/dvb/dvb-usb/lmedm04.c
index f2db012..40907df 100644
--- a/drivers/media/dvb/dvb-usb/lmedm04.c
+++ b/drivers/media/dvb/dvb-usb/lmedm04.c
@@ -591,9 +591,10 @@ static int lme2510_streaming_ctrl(struct dvb_usb_adapter *adap, int onoff)
 	else {
 		deb_info(1, "STM Steam Off");
 		/* mutex is here only to avoid collision with I2C */
-		ret = mutex_lock_interruptible(&adap->dev->i2c_mutex);
+		if (mutex_lock_interruptible(&adap->dev->i2c_mutex) < 0)
+			return -EAGAIN;
 
-		ret |= lme2510_usb_talk(adap->dev, clear_reg_3,
+		ret = lme2510_usb_talk(adap->dev, clear_reg_3,
 				sizeof(clear_reg_3), rbuf, rlen);
 		st->stream_on = 0;
 		st->i2c_talk_onoff = 1;
@@ -1017,12 +1018,13 @@ static int lme2510_powerup(struct dvb_usb_device *d, int onoff)
 	static u8 rbuf[1];
 	int ret, len = 3, rlen = 1;
 
-	ret = mutex_lock_interruptible(&d->i2c_mutex);
+	if (mutex_lock_interruptible(&d->i2c_mutex) < 0)
+		return -EAGAIN;
 
 	if (onoff)
-		ret |= lme2510_usb_talk(d, lnb_on, len, rbuf, rlen);
+		ret = lme2510_usb_talk(d, lnb_on, len, rbuf, rlen);
 	else
-		ret |= lme2510_usb_talk(d, lnb_off, len, rbuf, rlen);
+		ret = lme2510_usb_talk(d, lnb_off, len, rbuf, rlen);
 
 	st->i2c_talk_onoff = 1;
 
-- 
1.7.1

Re: [PATCH] [media] lmedm04: Do not unlock mutex if mutex_lock_interruptible failed

[Malcolm Priestley]

On Sat, 2011-04-16 at 00:40 +0400, Alexey Khoroshilov wrote:
> There are a couple of places where mutex_unlock() is called even 
> if mutex_lock_interruptible() failed. The patch fixes the issue.
> 
> Found by Linux Driver Verification project (linuxtesting.org).
> 
> Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
> ---
>  drivers/media/dvb/dvb-usb/lmedm04.c |   12 +++++++-----
>  1 files changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/media/dvb/dvb-usb/lmedm04.c b/drivers/media/dvb/dvb-usb/lmedm04.c
> index f2db012..40907df 100644
> --- a/drivers/media/dvb/dvb-usb/lmedm04.c
> +++ b/drivers/media/dvb/dvb-usb/lmedm04.c
> @@ -591,9 +591,10 @@ static int lme2510_streaming_ctrl(struct dvb_usb_adapter *adap, int onoff)
>  	else {
>  		deb_info(1, "STM Steam Off");
>  		/* mutex is here only to avoid collision with I2C */
> -		ret = mutex_lock_interruptible(&adap->dev->i2c_mutex);
> +		if (mutex_lock_interruptible(&adap->dev->i2c_mutex) < 0)
> +			return -EAGAIN;
>  
> -		ret |= lme2510_usb_talk(adap->dev, clear_reg_3,
> +		ret = lme2510_usb_talk(adap->dev, clear_reg_3,
>  				sizeof(clear_reg_3), rbuf, rlen);
>  		st->stream_on = 0;
>  		st->i2c_talk_onoff = 1;

Unfortunately dvb-usb does not provide -EAGAIN on streaming_ctrl
stopping and returns 0 instead.

This code is deliberate even if the i2c_mutex is unlocked, the code must
be executed, and is protected by on going i2c_mutex by the usb_mutex.

This patch produces a intermittent stall on channel change.

Regards


Malcolm

Re: [PATCH] [media] lmedm04: Do not unlock mutex if mutex_lock_interruptible failed

[Malcolm Priestley]

On Sat, 2011-04-16 at 01:01 +0100, Malcolm Priestley wrote:
> On Sat, 2011-04-16 at 00:40 +0400, Alexey Khoroshilov wrote:
> > There are a couple of places where mutex_unlock() is called even 
> > if mutex_lock_interruptible() failed. The patch fixes the issue.
> > 
> > Found by Linux Driver Verification project (linuxtesting.org).
> > 
> > Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
> > ---
> >  drivers/media/dvb/dvb-usb/lmedm04.c |   12 +++++++-----
> >  1 files changed, 7 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/media/dvb/dvb-usb/lmedm04.c b/drivers/media/dvb/dvb-usb/lmedm04.c
> > index f2db012..40907df 100644
> > --- a/drivers/media/dvb/dvb-usb/lmedm04.c
> > +++ b/drivers/media/dvb/dvb-usb/lmedm04.c
> > @@ -591,9 +591,10 @@ static int lme2510_streaming_ctrl(struct dvb_usb_adapter *adap, int onoff)
> >  	else {
> >  		deb_info(1, "STM Steam Off");
> >  		/* mutex is here only to avoid collision with I2C */
> > -		ret = mutex_lock_interruptible(&adap->dev->i2c_mutex);
> > +		if (mutex_lock_interruptible(&adap->dev->i2c_mutex) < 0)
> > +			return -EAGAIN;
> >  
> > -		ret |= lme2510_usb_talk(adap->dev, clear_reg_3,
> > +		ret = lme2510_usb_talk(adap->dev, clear_reg_3,
> >  				sizeof(clear_reg_3), rbuf, rlen);
> >  		st->stream_on = 0;
> >  		st->i2c_talk_onoff = 1;
> 
> Unfortunately dvb-usb does not provide -EAGAIN on streaming_ctrl
> stopping and returns 0 instead.
> 

I have added a patch to dvb-usb to return device errors to the demuxer

This patch may now be applied.

Tested by: Malcolm Priestley <tvboxspy@gmail.com>

Regards

Malcolm