V4L/DVB (8505): saa7134-empress.c: fix deadlock

ts_release() locked a mutex that videobuf_stop() also tried to obtain.
But ts_release() shouldn't hold that mutex at all.

Make empress_users atomic as well to prevent possible race condition.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

diff --git a/drivers/media/video/saa7134/saa7134-empress.c b/drivers/media/video/saa7134/saa7134-empress.c
index 8b3f95167781b38d6c466f03e87af23937b73e82..2ecfbd1b41fc0beb4104ac8130b5a3efb8dbaebb 100644 (file)
--- a/drivers/media/video/saa7134/saa7134-empress.c
+++ b/drivers/media/video/saa7134/saa7134-empress.c
@@ -89,14 +89,14 @@ static int ts_open(struct inode *inode, struct file *file)
        err = -EBUSY;
        if (!mutex_trylock(&dev->empress_tsq.vb_lock))
                goto done;
-       if (dev->empress_users)
+       if (atomic_read(&dev->empress_users))
                goto done_up;
 
        /* Unmute audio */
        saa_writeb(SAA7134_AUDIO_MUTE_CTRL,
                saa_readb(SAA7134_AUDIO_MUTE_CTRL) & ~(1 << 6));
 
-       dev->empress_users++;
+       atomic_inc(&dev->empress_users);
        file->private_data = dev;
        err = 0;
 
@@ -110,8 +110,6 @@ static int ts_release(struct inode *inode, struct file *file)
 {
        struct saa7134_dev *dev = file->private_data;
 
-       mutex_lock(&dev->empress_tsq.vb_lock);
-
        videobuf_stop(&dev->empress_tsq);
        videobuf_mmap_free(&dev->empress_tsq);
 
@@ -122,9 +120,7 @@ static int ts_release(struct inode *inode, struct file *file)
        saa_writeb(SAA7134_AUDIO_MUTE_CTRL,
                saa_readb(SAA7134_AUDIO_MUTE_CTRL) | (1 << 6));
 
-       dev->empress_users--;
-
-       mutex_unlock(&dev->empress_tsq.vb_lock);
+       atomic_dec(&dev->empress_users);
 
        return 0;
 }
@@ -447,7 +443,7 @@ static void empress_signal_update(struct work_struct *work)
                ts_reset_encoder(dev);
        } else {
                dprintk("video signal acquired\n");
-               if (dev->empress_users)
+               if (atomic_read(&dev->empress_users))
                        ts_init_encoder(dev);
        }
 }

diff --git a/drivers/media/video/saa7134/saa7134.h b/drivers/media/video/saa7134/saa7134.h
index ade4e19799e948ac4b588e00a91e45ca353d4a4a..ed20dd56379c6eb52df281f691b43f675390dc38 100644 (file)
--- a/drivers/media/video/saa7134/saa7134.h
+++ b/drivers/media/video/saa7134/saa7134.h
@@ -561,7 +561,7 @@ struct saa7134_dev {
        /* SAA7134_MPEG_EMPRESS only */
        struct video_device        *empress_dev;
        struct videobuf_queue      empress_tsq;
-       unsigned int               empress_users;
+       atomic_t                   empress_users;
        struct work_struct         empress_workqueue;
        int                        empress_started;