On 09-12-2011 23:37, Andreas Oberritter wrote:
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@xxxxxxxxxx> 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@xxxxxxxxxxx>
Andreas,
Thanks for the patch!
Devin,
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))
The only change here is that it will now use dvb_shutdown_timeout instead of
(dvb_shutdown_timeout * HZ + 1).
This makes sense.
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();
This is just a memory barrier to warrant that all CPU's will consider the new value for release_jiffies.
Probably Andreas added it because he noticed some race condition.
In any case, this won't cause any regressions.
+ }
ret = dvb_generic_release (inode, file);
if (dvbdev->users == -1) {
+ wake_up(&fepriv->wait_queue);
This is the only hook that changes the core behavior.
if (fepriv->exit != DVB_FE_NO_EXIT) {
fops_put(file->f_op);
file->f_op = NULL;
With this change, the current code at dvb_frontend_release() wil; be:
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;
wake_up(&dvbdev->wait_queue);
}
if (fe->ops.ts_bus_ctrl)
fe->ops.ts_bus_ctrl(fe, 0);
}
The addition of a wake_up there is that the wake_up thread will be called
also when fepriv->exit == DVB_FE_NO_EXIT. This seems to make sense, as
dvb_frontend_thread() explicitly tests for it at:
wait_event_interruptible_timeout(fepriv->wait_queue,
dvb_frontend_should_wakeup(fe) || kthread_should_stop()
|| freezing(current),
fepriv->delay);
as dvb_frontend_should_wakeup(fe) is defined (after applying this patch) as:
static int dvb_frontend_is_exiting(struct dvb_frontend *fe)
{
struct dvb_frontend_private *fepriv = fe->frontend_priv;
if (fepriv->exit != DVB_FE_NO_EXIT)
return 1;
if (fepriv->dvbdev->writers == 1)
if (time_after_eq(jiffies, fepriv->release_jiffies +
dvb_shutdown_timeout * HZ))
return 1;
return 0;
}
static int dvb_frontend_should_wakeup(struct dvb_frontend *fe)
{
struct dvb_frontend_private *fepriv = fe->frontend_priv;
if (fepriv->wakeup) {
fepriv->wakeup = 0;
return 1;
}
return dvb_frontend_is_exiting(fe);
}
So, this code makes sense to me. Btw, a wait queue can wait even without
an explicit call, since it is just something like [1]:
do schedule() while (!condition);
So, all this patch would hurt would be to increase the chance for us to
detect a bug that it is already there.
Devin,
I'll do some tests here with a few devices, but, in principle, I don't see
any reason why not applying this patch. So, except if I detect something wrong
on my tests, of if you you point us for a regression caused by this change,
I'll apply it.
Of course, it would be nice if Andreas could add some comments, but if he doesn't,
I can write something. It won't be the first patch that the maintainer would
need to insert some description.
Regards,
Mauro.
[1] The actual implementation is a more complex than that loop. In this
specific case, as it uses the interruptible version, any signal would
also wake this thread.
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