[pvrusb2] Looking for kernel oops evidence...

xavier.gnata at free.fr xavier.gnata at free.fr
Sat Sep 10 04:59:39 CDT 2005

Selon Mike Isely <isely at isely.net>:

> I've had one new report of kernel oops with the pvrusb2 driver.  Actually,
> it isn't "new"; the person only reported it to me a few days ago though he
> has been seeing this problem for a long time apparently.
> I'm looking into this now, but just from inspecting the code this looks to
> be an impossible condition.  The null pointer he's hit can only happen if
> the structure in question has been scribbled on or deleted.  But (1) the
> only place that pointer gets set to null is when the buffer is freed and
> that only happens when streaming is being torn down (but his report
> implies that this is happening for him in the middle of streaming), and
> (2) if it got scribbled on I'd expect to see a garbage value not zero.
> I'm also a little puzzled as to why this is the *only* report I've gotten
> of a problem like this.  It seems like if there is a race or dangling
> pointer problem of this nature then by now somebody else should have
> gotten burned by it.  So I was just wondering - has ANYONE here
> experienced a problem similar to the quoted text below?
> (The person who reported this is not on the mailing list so I've deleted
> identifying info from the message.)
>   -Mike
> <blockquote>
> Hello!
> I have been using your driver for two months now and i am very happy with it.
> However, i have an issue with it that happens from times to times: after
> keeping mplayer running for a long time (basically, all the night), i get a
> kernel oops :( Sometimes, mplayer justs exits without crashing the driver.
> I have captured the kernel logs, which you can find here:
> [deleted]
> It happens in pvr2_buffer_set_idle, in the following line:
> list_add_tail(&bp->list_overhead,&sp->idle_list);
> it seems that sp is null...
> Do you have an idea of what can be happening there?
> If you need more information, you can ask me!
> </blockquote>


It looks strange...
I have try to plug/unplug the card very quickly but I can't reprodude that :(
We may add a debug test just before this line to store important pointers values
into the logs when sp is NULL (ok that is trivial so not very helpful ;))

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