[linux-dvb] Re: reading two elementary PIDs (Aud and Vid) atonce

[Holger Waechtler]

Hi Matt,

there are many things changed since your patch, could you please regenerate your patch using "diff -pu" so that I can see the function names?

thanks,

Holger



Matt Davis wrote:

On Thursday 31 October 2002 04:07 pm, Mike Doyle wrote:

Does this mean I should be trying another way of getting two Elementary
streams (any suggestions)?

If not, is there a fix? Or work around?

thanks again
Mike

When trying to do the same thing, I found in the "old" driver that when DmxDevRead was called it locked the underlying dmxdev mutex so that all other reads were blocked. A second process would grab the lock and starve the first process because of the race condition set up with two processes trying to read the demux device. The way we got around it was to add a filter specific mutex and to use this mutex when DmxDevRead was called, instead of locking the dmxdev mutex. This allowed multiple filters to be read at one time, thereby fixing the problem. We are in the process of converting to the new drivers so I do not yet know if the same problem exists there...

Here is the patch to the old driver if it is of any use... hope this helps.


[mdavis cvs]$ diff -ru DVB/ temp/DVB/
diff -ru DVB/driver/dmxdev.c temp/DVB/driver/dmxdev.c
--- DVB/driver/dmxdev.c Thu Aug 1 11:46:11 2002
+++ temp/DVB/driver/dmxdev.c Thu Aug 15 12:49:57 2002
@@ -722,6 +726,7 @@
return -EMFILE;
}
dmxdevfilter=&dmxdev->filter[i];
+ sema_init(&dmxdevfilter->mutex, 1);
file->private_data=dmxdevfilter;
DmxDevBufferInit(&dmxdevfilter->buffer);
@@ -747,6 +752,11 @@
up(&dmxdev->mutex);
return -EINVAL;
}
+ + if (down_interruptible(&dmxdevfilter->mutex)) {
+ up(&dmxdev->mutex);
+ return -ERESTARTSYS;
+ }
DmxDevFilterStop(dmxdevfilter);
DmxDevFilterReset(dmxdevfilter);
@@ -761,6 +771,7 @@
}
DmxDevFilterStateSet(dmxdevfilter, DMXDEV_STATE_FREE);
wake_up(&dmxdevfilter->buffer.queue);
+ up(&dmxdevfilter->mutex);
up(&dmxdev->mutex);
//printk("free filters = %d\n", DmxDevFilterNum(dmxdev));
return 0;
@@ -907,7 +924,7 @@
dmxdev_filter_t *dmxdevfilter=DmxDevFile2Filter(dmxdev, file);
int ret=0;
- if (down_interruptible(&dmxdev->mutex))
+ if (down_interruptible(&dmxdevfilter->mutex))
return -ERESTARTSYS;
if (dmxdevfilter->type==DMXDEV_TYPE_SEC)
@@ -916,7 +933,7 @@
ret=DmxDevBufferRead(&dmxdevfilter->buffer, file->f_flags&O_NONBLOCK, buf, count, ppos);
- up(&dmxdev->mutex);
+ up(&dmxdevfilter->mutex);
return ret;
}
@@ -937,14 +954,26 @@
switch (cmd) {
case DMX_START: + if (down_interruptible(&dmxdevfilter->mutex)) {
+ up(&dmxdev->mutex);
+ return -ERESTARTSYS;
+ }
+
if (dmxdevfilter->state<DMXDEV_STATE_SET)
ret=-EINVAL;
else
ret=DmxDevFilterStart(dmxdevfilter);
+
+ up(&dmxdevfilter->mutex);
break;
case DMX_STOP: + if (down_interruptible(&dmxdevfilter->mutex)) {
+ up(&dmxdev->mutex);
+ return -ERESTARTSYS;
+ }
ret=DmxDevFilterStop(dmxdevfilter);
+ up(&dmxdevfilter->mutex);
break;
case DMX_SET_FILTER: @@ -954,8 +983,14 @@
if (copy_from_user(&params, parg, sizeof(params)))
ret=-EFAULT;
- else
+ else {
+ if (down_interruptible(&dmxdevfilter->mutex)) {
+ up(&dmxdev->mutex);
+ return -ERESTARTSYS;
+ }
ret=DmxDevFilterSet(dmxdev, dmxdevfilter, &params);
+ up(&dmxdevfilter->mutex);
+ }
break;
}
@@ -965,13 +1000,24 @@
if (copy_from_user(&params, parg, sizeof(params)))
ret=-EFAULT;
- else
+ else {
+ if (down_interruptible(&dmxdevfilter->mutex)) {
+ up(&dmxdev->mutex);
+ return -ERESTARTSYS;
+ }
ret=DmxDevPesFilterSet(dmxdev, dmxdevfilter, &params);
+ up(&dmxdevfilter->mutex);
+ }
break;
}
case DMX_SET_BUFFER_SIZE: + if (down_interruptible(&dmxdevfilter->mutex)) {
+ up(&dmxdev->mutex);
+ return -ERESTARTSYS;
+ }
ret=DmxDevSetBufferSize(dmxdevfilter, arg);
+ up(&dmxdevfilter->mutex);
break;
case DMX_GET_EVENT: diff -ru DVB/driver/dmxdev.h temp/DVB/driver/dmxdev.h
--- DVB/driver/dmxdev.h Mon Oct 29 05:51:26 2001
+++ temp/DVB/driver/dmxdev.h Wed Aug 7 15:08:30 2002
@@ -96,6 +96,8 @@
struct dmxdev_s *dev;
dmxdev_buffer_t buffer;
+ struct semaphore mutex;
+
// only for sections
struct timer_list timer;
int todo;

--
Info:
To unsubscribe send a mail to [EMAIL PROTECTED] with "unsubscribe linux-dvb" as subject.