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Subject[120/146] [media] cx88: fix locking of sub-driver operations
2.6.38-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Jonathan Nieder <jrnieder@gmail.com>

commit 1fe70e963028f34ba5e32488a7870ff4b410b19b upstream.

The BKL conversion of this driver seems to have gone wrong.
Loading the cx88-blackbird driver deadlocks.

The cause: mpeg_ops::open in the cx2388x blackbird driver acquires the
device lock and calls the sub-driver's request_acquire, which tries to
acquire the lock again. Fix it by clarifying the semantics of
request_acquire, request_release, advise_acquire, and advise_release:
now all will rely on the caller to acquire the device lock.

Based on work by Ben Hutchings <ben@decadent.org.uk>.

Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=31962

Reported-by: Andi Huber <hobrom@gmx.at>
Tested-by: Andi Huber <hobrom@gmx.at>
Tested-by: Marlon de Boer <marlon@hyves.nl>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/media/video/cx88/cx88-blackbird.c | 4 ++--
drivers/media/video/cx88/cx88-dvb.c | 3 +--
drivers/media/video/cx88/cx88-mpeg.c | 4 ----
drivers/media/video/cx88/cx88.h | 3 ++-
4 files changed, 5 insertions(+), 9 deletions(-)
--- a/drivers/media/video/cx88/cx88-blackbird.c
+++ b/drivers/media/video/cx88/cx88-blackbird.c
@@ -1125,13 +1125,13 @@ static int mpeg_release(struct file *fil

/* Make sure we release the hardware */
drv = cx8802_get_driver(dev, CX88_MPEG_BLACKBIRD);
- mutex_unlock(&dev->core->lock);
-
if (drv)
drv->request_release(drv);

atomic_dec(&dev->core->mpeg_users);

+ mutex_unlock(&dev->core->lock);
+
return 0;
}

--- a/drivers/media/video/cx88/cx88-dvb.c
+++ b/drivers/media/video/cx88/cx88-dvb.c
@@ -134,8 +134,6 @@ static int cx88_dvb_bus_ctrl(struct dvb_

mutex_lock(&dev->core->lock);
drv = cx8802_get_driver(dev, CX88_MPEG_DVB);
- mutex_unlock(&dev->core->lock);
-
if (drv) {
if (acquire){
dev->frontends.active_fe_id = fe_id;
@@ -145,6 +143,7 @@ static int cx88_dvb_bus_ctrl(struct dvb_
dev->frontends.active_fe_id = 0;
}
}
+ mutex_unlock(&dev->core->lock);

return ret;
}
--- a/drivers/media/video/cx88/cx88-mpeg.c
+++ b/drivers/media/video/cx88/cx88-mpeg.c
@@ -624,13 +624,11 @@ static int cx8802_request_acquire(struct

if (drv->advise_acquire)
{
- mutex_lock(&drv->core->lock);
core->active_ref++;
if (core->active_type_id == CX88_BOARD_NONE) {
core->active_type_id = drv->type_id;
drv->advise_acquire(drv);
}
- mutex_unlock(&drv->core->lock);

mpeg_dbg(1,"%s() Post acquire GPIO=%x\n", __func__, cx_read(MO_GP0_IO));
}
@@ -643,14 +641,12 @@ static int cx8802_request_release(struct
{
struct cx88_core *core = drv->core;

- mutex_lock(&drv->core->lock);
if (drv->advise_release && --core->active_ref == 0)
{
drv->advise_release(drv);
core->active_type_id = CX88_BOARD_NONE;
mpeg_dbg(1,"%s() Post release GPIO=%x\n", __func__, cx_read(MO_GP0_IO));
}
- mutex_unlock(&drv->core->lock);

return 0;
}
--- a/drivers/media/video/cx88/cx88.h
+++ b/drivers/media/video/cx88/cx88.h
@@ -500,7 +500,8 @@ struct cx8802_driver {
/* Caller must _not_ hold core->lock */
int (*probe)(struct cx8802_driver *drv);

- /* Caller must hold core->lock */
+ /* Callers to the following functions must hold core->lock */
+
int (*remove)(struct cx8802_driver *drv);

/* MPEG 8802 -> mini driver - Access for hardware control */



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