[PATCH] DVB: dvb_frontend: fix delayed thread exit

Andreas Oberritter
2011-12-10T01:37:06Z

On 10.12.2011 00:43, Mauro Carvalho Chehab wrote:
> On 09-12-2011 21:37, Mauro Carvalho Chehab wrote:
>> On 09-12-2011 20:33, Devin Heitmueller wrote:
>>> On Fri, Dec 9, 2011 at 5:11 PM, Mauro Carvalho Chehab
>>> <mchehab@redhat.com> wrote:
>>>>> Could someone explain reason for that?
>>>>
>>>>
>>>> I dunno, but I think this needs to be fixed, at least when the frontend
>>>> is opened with O_NONBLOCK.
>>>
>>> Are you doing the drx-k firmware load on dvb_init()? That could
>>> easily take 4 seconds.
>>
>> No. The firmware were opened previously.
>
> Maybe the delay is due to this part of dvb_frontend.c:
>
> static int dvb_mfe_wait_time = 5;
> ...
> int mferetry = (dvb_mfe_wait_time << 1);
>
> mutex_unlock (&adapter->mfe_lock);
> while (mferetry-- && (mfedev->users != -1 ||
> mfepriv->thread != NULL)) {
> if(msleep_interruptible(500)) {
> if(signal_pending(current))
> return -EINTR;
> }
> }

I haven't looked at the mfe code, but in case it's waiting for the
frontend thread to exit, there's a problem that causes the thread
not to exit immediately. Here's a patch that's been sitting in my
queue for a while:

---

Signed-off-by: Andreas Oberritter <obi@linuxtv.org>

diff --git a/linux/drivers/media/dvb/dvb-core/dvb_frontend.c b/linux/drivers/media/dvb/dvb-core/dvb_frontend.c
index 7784d74..6823c2b 100644
--- a/linux/drivers/media/dvb/dvb-core/dvb_frontend.c 2011-09-07 12:32:24.000000000 +0200
+++ a/linux/drivers/media/dvb/dvb-core/dvb_frontend.c 2011-09-13 15:55:48.865742791 +0200
@@ -514,7 +514,7 @@
return 1;

if (fepriv->dvbdev->writers == 1)
- if (time_after(jiffies, fepriv->release_jiffies +
+ if (time_after_eq(jiffies, fepriv->release_jiffies +
dvb_shutdown_timeout * HZ))
return 1;

@@ -2070,12 +2070,15 @@

dprintk ("%s\n", __func__);

- if ((file->f_flags & O_ACCMODE) != O_RDONLY)
+ if ((file->f_flags & O_ACCMODE) != O_RDONLY) {
fepriv->release_jiffies = jiffies;
+ mb();
+ }

ret = dvb_generic_release (inode, file);

if (dvbdev->users == -1) {
+ wake_up(&fepriv->wait_queue);
if (fepriv->exit != DVB_FE_NO_EXIT) {
fops_put(file->f_op);
file->f_op = NULL;