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[linux-dvb] Re: Kernel OOPS



Klaus Schmidinger wrote:

Holger Waechtler wrote:

Johannes Stezenbach wrote:

mws@renzel.net wrote:

i am playing around with the DVR device for playing back a TS which
was recorded from the DVR device.
...

The kernel is configured a an SMP Kernel and Preemptible feature.

That's a recipe for disaster -- the dvr playback code in the av7110
is seriously b0rked. Apart from the bug you found, the dvr device
does not support non-blocking writes, and if you try to use multiple
threads and do video ioctls from one thread while another thread
blocks in dvr write() your machine will lock up...

The output from dmesg after Oopsing is :

bad: scheduling while atomic! Call Trace:

Just for the record, this is not an Oops, just an indication that the
driver is buggy.

anybody you can help me out of this?

The problem is that the av7110 hardware does not support TS playback.
The driver tries to work around this by remuxing the TS into PES and
feeding PES to the hardware. IMHO this code should be dropped rather
than attempted to fix. Remuxing should be done in user space. VDR
does the right thing.
calling the PES unpacking process a 'remuxing' is kind of flattered,
not? Forcing everybody to misuse the lowlevel-API instead of highlevel
access just because the av711x driver is broken...

Well, Holger, you keep repeating over and over that the av7110 driver
is "broken" and that this is "ancient" hardware and how great "modern"
hardware ist - but IMHO you totally neglect that the av7110 still is probably
the most widely used hardware! People have invested real money into these
full featured DVB cards and just don't want to throw them away.
Plus, there just isn't any reasonable alternative
And don't say "use a budget card and do replay over the graphics card" - the
average user wants to insert *ONE* card into his PC and use that one for
recording AND replay. Besides: replay over graphics card means MPEG decoding
in software, which in turn requires more CPU power... Also: are there any
budget cards already that have drivers that support CAMs? I have to admit that
I don't know that.

So, what about just fixing the av7110 driver?
(nope, let's design cheap and cool hardware instead - evil things need to get changed, not worked around - ;)
we'll keep you posted...

Holger




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