On Mon, 2009-05-18 at 05:07 +0200, hermann pitton wrote:
> Am Montag, den 18.05.2009, 10:13 +0800 schrieb figo.zhang:
> > saa7134-video.c: poll method lose race condition
> > 
> > 
> > Signed-off-by: Figo.zhang <figo.zh...@kolorific.com>
> > --- 
> > drivers/media/video/saa7134/saa7134-video.c |    9 ++++++---
> >  1 files changed, 6 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/media/video/saa7134/saa7134-video.c 
> > b/drivers/media/video/saa7134/saa7134-video.c
> > index 493cad9..95733df 100644
> > --- a/drivers/media/video/saa7134/saa7134-video.c
> > +++ b/drivers/media/video/saa7134/saa7134-video.c
> > @@ -1423,11 +1423,13 @@ video_poll(struct file *file, struct 
> > poll_table_struct *wait)
> >  {
> >     struct saa7134_fh *fh = file->private_data;
> >     struct videobuf_buffer *buf = NULL;
> > +   unsigned int rc = 0;
> >  
> >     if (V4L2_BUF_TYPE_VBI_CAPTURE == fh->type)
> >             return videobuf_poll_stream(file, &fh->vbi, wait);
> >  
> >     if (res_check(fh,RESOURCE_VIDEO)) {
> > +           mutex_lock(&fh->cap.vb_lock);
> >             if (!list_empty(&fh->cap.stream))
> >                     buf = list_entry(fh->cap.stream.next, struct 
> > videobuf_buffer, stream);
> >     } else {
> > @@ -1446,13 +1448,14 @@ video_poll(struct file *file, struct 
> > poll_table_struct *wait)
> >     }
> >  
> >     if (!buf)
> > -           return POLLERR;
> > +           rc = POLLERR;
> >  
> >     poll_wait(file, &buf->done, wait);
> >     if (buf->state == VIDEOBUF_DONE ||
> >         buf->state == VIDEOBUF_ERROR)
> > -           return POLLIN|POLLRDNORM;
> > -   return 0;
> > +           rc = POLLIN|POLLRDNORM;
> > +   mutex_unlock(&fh->cap.vb_lock);
> > +   return rc;
> >  
> >  err:
> >     mutex_unlock(&fh->cap.vb_lock);
> > 
> > 
> 
> Can you please give some description on what your patch might do
> something?
> 
> Or are you a robot?
> 
> Then, please give us your serial number, production year, and when we
> can expect you are out of duty and replaced ;)
> 
> Cheers,
> Hermann
> 
> 
> 

hi, I just using the saa7134 chip to do a video capture card. The
saa7134 driver in linux kernel, i found that the poll method have lose 
race condition for "RESOURCE_VIDEO". It have better to add a mutex lock.

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