Commit 1e4597e8 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Mauro Carvalho Chehab

V4L/DVB (5818): CinergyT2: fix flush_workqueue() vs work->func() deadlock

Spotted and tested by Thomas Sattler <tsattler@gmx.de>.

cinergyT2.c does cancel_delayed_work() + flush_scheduled_work() while
holding cinergyt2->sem. This leads to deadlock because work->func()
needs the same mutex to complete. Another bug is that this code in fact
can't reliably stop the re-arming delayed_work.

Convert this code to use cancel_rearming_delayed_work() and move it
out of ->sem. Another mutex, ->wq_sem, was added to protect against the
concurrent open/resume.

This patch is a horrible hack to fix the lockup which happens in practice.
As Dmitry Torokhov pointed out this driver has other problems and needs
further changes.
Signed-off-by: default avatarOleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@infradead.org>
parent f057131f
......@@ -118,6 +118,7 @@ struct cinergyt2 {
struct dvb_demux demux;
struct usb_device *udev;
struct mutex sem;
struct mutex wq_sem;
struct dvb_adapter adapter;
struct dvb_device *fedev;
struct dmxdev dmxdev;
......@@ -482,14 +483,14 @@ static int cinergyt2_open (struct inode *inode, struct file *file)
struct cinergyt2 *cinergyt2 = dvbdev->priv;
int err = -ERESTARTSYS;
if (cinergyt2->disconnect_pending || mutex_lock_interruptible(&cinergyt2->sem))
return -ERESTARTSYS;
if (cinergyt2->disconnect_pending || mutex_lock_interruptible(&cinergyt2->wq_sem))
goto out;
if ((err = dvb_generic_open(inode, file))) {
mutex_unlock(&cinergyt2->sem);
return err;
}
if (mutex_lock_interruptible(&cinergyt2->sem))
goto out_unlock1;
if ((err = dvb_generic_open(inode, file)))
goto out_unlock2;
if ((file->f_flags & O_ACCMODE) != O_RDONLY) {
cinergyt2_sleep(cinergyt2, 0);
......@@ -498,8 +499,12 @@ static int cinergyt2_open (struct inode *inode, struct file *file)
atomic_inc(&cinergyt2->inuse);
out_unlock2:
mutex_unlock(&cinergyt2->sem);
return 0;
out_unlock1:
mutex_unlock(&cinergyt2->wq_sem);
out:
return err;
}
static void cinergyt2_unregister(struct cinergyt2 *cinergyt2)
......@@ -519,15 +524,17 @@ static int cinergyt2_release (struct inode *inode, struct file *file)
struct dvb_device *dvbdev = file->private_data;
struct cinergyt2 *cinergyt2 = dvbdev->priv;
mutex_lock(&cinergyt2->sem);
mutex_lock(&cinergyt2->wq_sem);
if (!cinergyt2->disconnect_pending && (file->f_flags & O_ACCMODE) != O_RDONLY) {
cancel_delayed_work(&cinergyt2->query_work);
flush_scheduled_work();
cancel_rearming_delayed_work(&cinergyt2->query_work);
mutex_lock(&cinergyt2->sem);
cinergyt2_sleep(cinergyt2, 1);
mutex_unlock(&cinergyt2->sem);
}
mutex_unlock(&cinergyt2->sem);
mutex_unlock(&cinergyt2->wq_sem);
if (atomic_dec_and_test(&cinergyt2->inuse) && cinergyt2->disconnect_pending) {
warn("delayed unregister in release");
......@@ -838,13 +845,13 @@ static int cinergyt2_register_rc(struct cinergyt2 *cinergyt2)
static void cinergyt2_unregister_rc(struct cinergyt2 *cinergyt2)
{
cancel_delayed_work(&cinergyt2->rc_query_work);
cancel_rearming_delayed_work(&cinergyt2->rc_query_work);
input_unregister_device(cinergyt2->rc_input_dev);
}
static inline void cinergyt2_suspend_rc(struct cinergyt2 *cinergyt2)
{
cancel_delayed_work(&cinergyt2->rc_query_work);
cancel_rearming_delayed_work(&cinergyt2->rc_query_work);
}
static inline void cinergyt2_resume_rc(struct cinergyt2 *cinergyt2)
......@@ -907,6 +914,7 @@ static int cinergyt2_probe (struct usb_interface *intf,
usb_set_intfdata (intf, (void *) cinergyt2);
mutex_init(&cinergyt2->sem);
mutex_init(&cinergyt2->wq_sem);
init_waitqueue_head (&cinergyt2->poll_wq);
INIT_DELAYED_WORK(&cinergyt2->query_work, cinergyt2_query);
......@@ -974,11 +982,8 @@ static void cinergyt2_disconnect (struct usb_interface *intf)
{
struct cinergyt2 *cinergyt2 = usb_get_intfdata (intf);
flush_scheduled_work();
cinergyt2_unregister_rc(cinergyt2);
cancel_delayed_work(&cinergyt2->query_work);
cancel_rearming_delayed_work(&cinergyt2->query_work);
wake_up_interruptible(&cinergyt2->poll_wq);
cinergyt2->demux.dmx.close(&cinergyt2->demux.dmx);
......@@ -992,21 +997,21 @@ static int cinergyt2_suspend (struct usb_interface *intf, pm_message_t state)
{
struct cinergyt2 *cinergyt2 = usb_get_intfdata (intf);
if (cinergyt2->disconnect_pending || mutex_lock_interruptible(&cinergyt2->sem))
if (cinergyt2->disconnect_pending || mutex_lock_interruptible(&cinergyt2->wq_sem))
return -ERESTARTSYS;
if (1) {
struct cinergyt2 *cinergyt2 = usb_get_intfdata (intf);
cinergyt2_suspend_rc(cinergyt2);
cancel_delayed_work(&cinergyt2->query_work);
cancel_rearming_delayed_work(&cinergyt2->query_work);
mutex_lock(&cinergyt2->sem);
if (cinergyt2->streaming)
cinergyt2_stop_stream_xfer(cinergyt2);
flush_scheduled_work();
cinergyt2_sleep(cinergyt2, 1);
mutex_unlock(&cinergyt2->sem);
}
mutex_unlock(&cinergyt2->sem);
mutex_unlock(&cinergyt2->wq_sem);
return 0;
}
......@@ -1014,9 +1019,15 @@ static int cinergyt2_resume (struct usb_interface *intf)
{
struct cinergyt2 *cinergyt2 = usb_get_intfdata (intf);
struct dvbt_set_parameters_msg *param = &cinergyt2->param;
int err = -ERESTARTSYS;
if (cinergyt2->disconnect_pending || mutex_lock_interruptible(&cinergyt2->sem))
return -ERESTARTSYS;
if (cinergyt2->disconnect_pending || mutex_lock_interruptible(&cinergyt2->wq_sem))
goto out;
if (mutex_lock_interruptible(&cinergyt2->sem))
goto out_unlock1;
err = 0;
if (!cinergyt2->sleeping) {
cinergyt2_sleep(cinergyt2, 0);
......@@ -1029,7 +1040,10 @@ static int cinergyt2_resume (struct usb_interface *intf)
cinergyt2_resume_rc(cinergyt2);
mutex_unlock(&cinergyt2->sem);
return 0;
out_unlock1:
mutex_unlock(&cinergyt2->wq_sem);
out:
return err;
}
static const struct usb_device_id cinergyt2_table [] __devinitdata = {
......
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