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Message-ID: <20070702144817.GA455@tv-sign.ru>
Date: Mon, 2 Jul 2007 18:48:17 +0400
From: Oleg Nesterov <oleg@...sign.ru>
To: Markus Rechberger <mrechberger@...il.com>,
Mauro Carvalho Chehab <mchehab@...radead.org>,
Thomas Sattler <tsattler@....de>
Cc: Alan Cox <alan@...rguk.ukuu.org.uk>, Daniel Mack <daniel@...u.de>,
Dmitry Torokhov <dmitry.torokhov@...il.com>,
Holger Waechtler <holger@...u.de>, Ingo Molnar <mingo@...e.hu>,
linux-kernel@...r.kernel.org
Subject: [PATCH] dvb/cinergyT2: fix flush_workqueue() vs work->func() deadlock
Spotted and tested by Thomas Sattler <tsattler@....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: Oleg Nesterov <oleg@...sign.ru>
--- t/drivers/media/dvb/cinergyT2/cinergyT2.c~cinergy 2007-06-19 17:09:15.000000000 +0400
+++ t/drivers/media/dvb/cinergyT2/cinergyT2.c 2007-06-30 18:01:43.000000000 +0400
@@ -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
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
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 ino
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
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_i
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
{
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 +997,22 @@ static int cinergyt2_suspend (struct usb
{
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 +1020,15 @@ static int cinergyt2_resume (struct usb_
{
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 +1041,10 @@ static int cinergyt2_resume (struct usb_
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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