Skip to content

Commit

Permalink
[media] dvb_usb_v2: replace Kernel userspace lock with wait queue
Browse files Browse the repository at this point in the history 
There was sync mutex which was held over userspace. That is very
wrong and could cause deadlock if different userspace process is
used to "unlock". Wait queue seems to be correct solution for
that kind of synchronizing issue so use it instead.
lock debug gives following bug report:
================================================
[ BUG: lock held when returning to user space! ]
3.9.0-rc1+ torvalds#38 Tainted: G           O
------------------------------------------------
tzap/4614 is leaving the kernel with locks still held!
1 lock held by tzap/4614:

Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
  • Loading branch information
@palosaari
palosaari authored and Mauro Carvalho Chehab committed Mar 23, 2013
1 parent 028c70f commit bdecbe4
Show file tree
Hide file tree
Showing 2 changed files with 41 additions and 17 deletions.
5 changes: 4 additions & 1 deletion drivers/media/usb/dvb-usb-v2/dvb_usb.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -329,13 +329,16 @@ struct dvb_usb_adapter {
u8 feed_count;
u8 max_feed_count;
s8 active_fe;
#define ADAP_INIT 0
#define ADAP_SLEEP 1
#define ADAP_STREAMING 2
unsigned long state_bits;

/* dvb */
struct dvb_adapter dvb_adap;
struct dmxdev dmxdev;
struct dvb_demux demux;
struct dvb_net dvb_net;
struct mutex sync_mutex;

struct dvb_frontend *fe[MAX_NO_OF_FE_PER_ADAP];
int (*fe_init[MAX_NO_OF_FE_PER_ADAP]) (struct dvb_frontend *);
Expand Down
53 changes: 37 additions & 16 deletions drivers/media/usb/dvb-usb-v2/dvb_usb_core.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -253,6 +253,13 @@ static int dvb_usbv2_adapter_stream_exit(struct dvb_usb_adapter *adap)
return usb_urb_exitv2(&adap->stream);
}

static int wait_schedule(void *ptr)
{
schedule();

return 0;
}

static inline int dvb_usb_ctrl_feed(struct dvb_demux_feed *dvbdmxfeed,
int count)
{
Expand All @@ -266,6 +273,9 @@ static inline int dvb_usb_ctrl_feed(struct dvb_demux_feed *dvbdmxfeed,
dvbdmxfeed->pid, dvbdmxfeed->index,
(count == 1) ? "on" : "off");

wait_on_bit(&adap->state_bits, ADAP_INIT, wait_schedule,
TASK_UNINTERRUPTIBLE);

if (adap->active_fe == -1)
return -EINVAL;

Expand All @@ -283,11 +293,14 @@ static inline int dvb_usb_ctrl_feed(struct dvb_demux_feed *dvbdmxfeed,
"failed=%d\n", KBUILD_MODNAME,
ret);
usb_urb_killv2(&adap->stream);
goto err_mutex_unlock;
goto err_clear_wait;
}
}
usb_urb_killv2(&adap->stream);
mutex_unlock(&adap->sync_mutex);

clear_bit(ADAP_STREAMING, &adap->state_bits);
smp_mb__after_clear_bit();
wake_up_bit(&adap->state_bits, ADAP_STREAMING);
}

/* activate the pid on the device pid filter */
Expand All @@ -303,7 +316,7 @@ static inline int dvb_usb_ctrl_feed(struct dvb_demux_feed *dvbdmxfeed,
/* start feeding if it is first pid */
if (adap->feed_count == 1 && count == 1) {
struct usb_data_stream_properties stream_props;
mutex_lock(&adap->sync_mutex);
set_bit(ADAP_STREAMING, &adap->state_bits);
dev_dbg(&d->udev->dev, "%s: start feeding\n", __func__);

/* resolve input and output streaming paramters */
Expand All @@ -314,7 +327,7 @@ static inline int dvb_usb_ctrl_feed(struct dvb_demux_feed *dvbdmxfeed,
adap->fe[adap->active_fe],
&adap->ts_type, &stream_props);
if (ret < 0)
goto err_mutex_unlock;
goto err_clear_wait;
} else {
stream_props = adap->props->stream;
}
Expand Down Expand Up @@ -344,7 +357,7 @@ static inline int dvb_usb_ctrl_feed(struct dvb_demux_feed *dvbdmxfeed,
dev_err(&d->udev->dev, "%s: " \
"pid_filter_ctrl() failed=%d\n",
KBUILD_MODNAME, ret);
goto err_mutex_unlock;
goto err_clear_wait;
}
}

Expand All @@ -355,14 +368,16 @@ static inline int dvb_usb_ctrl_feed(struct dvb_demux_feed *dvbdmxfeed,
dev_err(&d->udev->dev, "%s: streaming_ctrl() " \
"failed=%d\n", KBUILD_MODNAME,
ret);
goto err_mutex_unlock;
goto err_clear_wait;
}
}
}

return 0;
err_mutex_unlock:
mutex_unlock(&adap->sync_mutex);
err_clear_wait:
clear_bit(ADAP_STREAMING, &adap->state_bits);
smp_mb__after_clear_bit();
wake_up_bit(&adap->state_bits, ADAP_STREAMING);
dev_dbg(&d->udev->dev, "%s: failed=%d\n", __func__, ret);
return ret;
}
Expand Down Expand Up @@ -435,8 +450,6 @@ static int dvb_usbv2_adapter_dvb_init(struct dvb_usb_adapter *adap)
goto err_dvb_net_init;
}

mutex_init(&adap->sync_mutex);

return 0;
err_dvb_net_init:
dvb_dmxdev_release(&adap->dmxdev);
Expand Down Expand Up @@ -500,7 +513,7 @@ static int dvb_usb_fe_init(struct dvb_frontend *fe)

if (!adap->suspend_resume_active) {
adap->active_fe = fe->id;
mutex_lock(&adap->sync_mutex);
set_bit(ADAP_INIT, &adap->state_bits);
}

ret = dvb_usbv2_device_power_ctrl(d, 1);
Expand All @@ -519,8 +532,11 @@ static int dvb_usb_fe_init(struct dvb_frontend *fe)
goto err;
}
err:
if (!adap->suspend_resume_active)
mutex_unlock(&adap->sync_mutex);
if (!adap->suspend_resume_active) {
clear_bit(ADAP_INIT, &adap->state_bits);
smp_mb__after_clear_bit();
wake_up_bit(&adap->state_bits, ADAP_INIT);
}

dev_dbg(&d->udev->dev, "%s: ret=%d\n", __func__, ret);
return ret;
Expand All @@ -534,8 +550,11 @@ static int dvb_usb_fe_sleep(struct dvb_frontend *fe)
dev_dbg(&d->udev->dev, "%s: adap=%d fe=%d\n", __func__, adap->id,
fe->id);

if (!adap->suspend_resume_active)
mutex_lock(&adap->sync_mutex);
if (!adap->suspend_resume_active) {
set_bit(ADAP_SLEEP, &adap->state_bits);
wait_on_bit(&adap->state_bits, ADAP_STREAMING, wait_schedule,
TASK_UNINTERRUPTIBLE);
}

if (adap->fe_sleep[fe->id]) {
ret = adap->fe_sleep[fe->id](fe);
Expand All @@ -555,7 +574,9 @@ static int dvb_usb_fe_sleep(struct dvb_frontend *fe)
err:
if (!adap->suspend_resume_active) {
adap->active_fe = -1;
mutex_unlock(&adap->sync_mutex);
clear_bit(ADAP_SLEEP, &adap->state_bits);
smp_mb__after_clear_bit();
wake_up_bit(&adap->state_bits, ADAP_SLEEP);
}

dev_dbg(&d->udev->dev, "%s: ret=%d\n", __func__, ret);
Expand Down

0 comments on commit bdecbe4

Please sign in to comment.