V4L/DVB (6583): Fix em28xx read stream locking

On some situations, closing an streaming application and re-opening were
returning -EBUSY.

Uses the same locking schema also present on cx88.

Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

1 files changed, 56 insertions, 21 deletions

diff --git a/drivers/media/video/em28xx/em28xx-video.c b/drivers/media/video/em28xx/em28xx-video.c
index 5b17ca9cad11..f0191779a8e2 100644
--- a/drivers/media/video/em28xx/em28xx-video.c
+++ b/drivers/media/video/em28xx/em28xx-video.c
@@ -225,6 +225,44 @@ static void video_mux(struct em28xx *dev, int index)
         }
 }
 
+/* Usage lock check functions */
+static int res_get(struct em28xx_fh *fh)
+{
+        struct em28xx    *dev = fh->dev;
+        int              rc   = 0;
+
+        /* This instance already has stream_on */
+        if (fh->stream_on)
+                return rc;
+
+        mutex_lock(&dev->lock);
+
+        if (dev->stream_on)
+                rc = -EINVAL;
+        else {
+                dev->stream_on = 1;
+                fh->stream_on  = 1;
+        }
+
+        mutex_unlock(&dev->lock);
+        return rc;
+}
+
+static int res_check(struct em28xx_fh *fh)
+{
+        return (fh->stream_on);
+}
+
+static void res_free(struct em28xx_fh *fh)
+{
+        struct em28xx    *dev = fh->dev;
+
+        mutex_lock(&dev->lock);
+        fh->stream_on = 0;
+        dev->stream_on = 0;
+        mutex_unlock(&dev->lock);
+}
+
 /*
  * em28xx_v4l2_open()
  * inits the device and starts isoc transfer
@@ -328,15 +366,16 @@ static int em28xx_v4l2_close(struct inode *inode, struct file *filp)
 
         em28xx_videodbg("users=%d\n", dev->users);
 
+
+        if (res_check(fh))
+                res_free(fh);
+
         mutex_lock(&dev->lock);
-        if (fh->reader == 1)
-               fh->reader = 0;
 
         if (dev->users == 1) {
-                dev->reader = 0;
-
                 em28xx_uninit_isoc(dev);
                 em28xx_release_buffers(dev);
+                dev->io = IO_NONE;
 
                 /* the device is already disconnect,
                    free the remaining resources */
@@ -377,16 +416,15 @@ em28xx_v4l2_read(struct file *filp, char __user * buf, size_t count,
         struct em28xx_fh *fh = filp->private_data;
         struct em28xx *dev = fh->dev;
 
+
+        if (unlikely(res_get(fh) < 0))
+                return -EBUSY;
+
         mutex_lock(&dev->lock);
 
         if (dev->type == V4L2_BUF_TYPE_VIDEO_CAPTURE)
                 em28xx_videodbg("V4l2_Buf_type_videocapture is set\n");
 
-        if (dev->reader > 0 && fh->reader == 0) {
-                mutex_unlock(&dev->lock);
-                return -EBUSY;
-        }
-
         if (dev->type == V4L2_BUF_TYPE_VBI_CAPTURE) {
                 em28xx_videodbg("V4L2_BUF_TYPE_VBI_CAPTURE is set\n");
                 em28xx_videodbg("not supported yet! ...\n");
@@ -425,9 +463,6 @@ em28xx_v4l2_read(struct file *filp, char __user * buf, size_t count,
                                 " the device again to choose the read method\n");
                 mutex_unlock(&dev->lock);
                 return -EINVAL;
-        } else {
-                dev->reader = 1;
-                fh->reader = 1;
         }
 
         if (dev->io == IO_NONE) {
@@ -499,6 +534,9 @@ static unsigned int em28xx_v4l2_poll(struct file *filp, poll_table * wait)
         struct em28xx_fh *fh = filp->private_data;
         struct em28xx *dev = fh->dev;
 
+        if (unlikely(res_get(fh) < 0))
+                return POLLERR;
+
         mutex_lock(&dev->lock);
 
         if (dev->state & DEV_DISCONNECTED) {
@@ -572,15 +610,10 @@ static int em28xx_v4l2_mmap(struct file *filp, struct vm_area_struct *vma)
         void             *pos;
         u32              i;
 
-        mutex_lock(&dev->lock);
-
-        if (dev->reader > 0 && fh->reader == 0) {
-                mutex_unlock(&dev->lock);
+        if (unlikely(res_get(fh) < 0))
                 return -EBUSY;
-        } else {
-                dev->reader = 1;
-                fh->reader = 1;
-        }
+
+        mutex_lock(&dev->lock);
 
         if (dev->state & DEV_DISCONNECTED) {
                 em28xx_videodbg("mmap: device not present\n");
@@ -1219,6 +1252,9 @@ static int em28xx_do_ioctl(struct inode *inode, struct file *filp,
                 if (list_empty(&dev->inqueue))
                         return -EINVAL;
 
+                if (unlikely(res_get(fh) < 0))
+                        return -EBUSY;
+
                 dev->stream = STREAM_ON;        /* FIXME: Start video capture here? */
 
                 em28xx_videodbg("VIDIOC_STREAMON: starting stream\n");
@@ -1243,7 +1279,6 @@ static int em28xx_do_ioctl(struct inode *inode, struct file *filp,
                         }
                 }
 
-                fh->reader = 0;
                 em28xx_empty_framequeues(dev);
                 mutex_unlock(&dev->lock);