From 3165ca2068855d7118d78396adce4c49a4e7f636 Mon Sep 17 00:00:00 2001 From: Devin Heitmueller Date: Mon, 4 May 2009 20:43:02 -0400 Subject: dvb_frontend: fix race condition resulting in dropped tuning commands From: Devin Heitmueller A race condition was detected in the case that putting the tuner to sleep takes an unusually long period of time, combined with applications that quickly close/open the dvb frontend. The kaffeine channel scanner closes and reopens the dvb frontend between each tuning attempt. If it takes an unusually longer period of time to put the tuner to sleep (for example, the Pinnacle 801e takes 660 ms), the dvb_frontend thread will still be in a running state (and hence fepriv->thread is still set) but the fepriv->exit field will still be zero. As a result, if a dvb_frontend_start() call arrives while the frontend thread is in the process of terminating, the call will return 0 without actually starting a new thread. This results in the tuning request being dropped. To address this, mark fepriv->exit as soon as we know the thread is going to be terminated, so that dvb_frontend_start() knows to start a new instance. Problem encountered with Kaffeine 0.8.7 doing ATSC scanning against the Pinnacle 801e tuner, in conjunction with new code to power down the xc5000 when not in use. Priority: normal Signed-off-by: Devin Heitmueller --- linux/drivers/media/dvb/dvb-core/dvb_frontend.c | 1 + 1 file changed, 1 insertion(+) (limited to 'linux/drivers/media/dvb/dvb-core') diff --git a/linux/drivers/media/dvb/dvb-core/dvb_frontend.c b/linux/drivers/media/dvb/dvb-core/dvb_frontend.c index da2890b22..d359f6841 100644 --- a/linux/drivers/media/dvb/dvb-core/dvb_frontend.c +++ b/linux/drivers/media/dvb/dvb-core/dvb_frontend.c @@ -554,6 +554,7 @@ restart: if (kthread_should_stop() || dvb_frontend_is_exiting(fe)) { /* got signal or quitting */ + fepriv->exit = 1; break; } -- cgit v1.2.3 From 3e94e24e59b323cdacd22598b28769753866bfc3 Mon Sep 17 00:00:00 2001 From: Mauro Carvalho Chehab Date: Tue, 12 May 2009 20:39:28 +0000 Subject: core: fix potential mutex_unlock without mutex_lock in dvb_dvr_read From: Simon Arlott dvb_dvr_read may unlock the dmxdev mutex and return -ENODEV, except this function is a file op and will never be called with the mutex held. There's existing mutex_lock and mutex_unlock around the actual read but it's commented out. These should probably be uncommented but the read blocks and this could block another non-blocking reader on the mutex instead. This change comments out the extra mutex_unlock. [akpm@linux-foundation.org: cleanups, simplification] Signed-off-by: Simon Arlott Signed-off-by: Andrew Morton Signed-off-by: Mauro Carvalho Chehab --- linux/drivers/media/dvb/dvb-core/dmxdev.c | 14 ++++---------- 1 file changed, 4 insertions(+), 10 deletions(-) (limited to 'linux/drivers/media/dvb/dvb-core') diff --git a/linux/drivers/media/dvb/dvb-core/dmxdev.c b/linux/drivers/media/dvb/dvb-core/dmxdev.c index c35fbb8d8..6d6121eb5 100644 --- a/linux/drivers/media/dvb/dvb-core/dmxdev.c +++ b/linux/drivers/media/dvb/dvb-core/dmxdev.c @@ -244,19 +244,13 @@ static ssize_t dvb_dvr_read(struct file *file, char __user *buf, size_t count, { struct dvb_device *dvbdev = file->private_data; struct dmxdev *dmxdev = dvbdev->priv; - int ret; - if (dmxdev->exit) { - mutex_unlock(&dmxdev->mutex); + if (dmxdev->exit) return -ENODEV; - } - //mutex_lock(&dmxdev->mutex); - ret = dvb_dmxdev_buffer_read(&dmxdev->dvr_buffer, - file->f_flags & O_NONBLOCK, - buf, count, ppos); - //mutex_unlock(&dmxdev->mutex); - return ret; + return dvb_dmxdev_buffer_read(&dmxdev->dvr_buffer, + file->f_flags & O_NONBLOCK, + buf, count, ppos); } static int dvb_dvr_set_buffer_size(struct dmxdev *dmxdev, -- cgit v1.2.3