[linux-dvb] [PATCH] budget_av / dvb_ca_en50221: fixes ci/cam handling especially on SMP machines

[Matthias Dahl]

Hi Oliver.

I can happily report that with the following two patches applied, I haven't 
seen a single case where the cam stopped working due to i/o errors or 
anything like it.

The budget_av patch is basically your patch just a bit extended which I 
thought was necessary to cover all relevant cases. Works just fine.

The dvb_ca_en50221 patch introduces the concept of slot lock that means, you 
can either read or write to a slot but concurrent i/o on a slot is no longer 
allowed. This case was already thought of and partly taken care of but 
unfortunately due to the missing locking mechanism, it just made the race 
condition harder to trigger but not impossible... especially on SMP systems 
where this is easier to hit. That's way I introduced a mutex. I left the 
original check in there but it actually never should get triggered anymore. 
Right now actually, if it gets triggered, one could assume the ci/cam is in 
an undefined state and trigger a reinit, like it's done on a few other 
places.

Could you please apply those patches to the dvb tree and maybe get into the 
official 2.6.27? Those bugs haven been around for quite some time now and 
without the patches, they are not so hard to trigger.

Thanks a lot for your help by the way!

So long,
matthias.
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