[mythtv-users] SUID root might hang your myth box

[Phil Blundell]

on Thu, Nov 18, 2004 at 01:48:40AM -0800, Joe Barnhart wrote:
> Why does this seemingly innocuous setting cause such a
> huge problem?  Why is it recommended?  Does the
> benefit outweigh the stress on my box turning it off
> and on a bunch of times trying to get the setting to
> work?

Making mythfrontsend setuid root allows it to set the video playback
thread to "realtime" priority, which means it will always have
precedence over any other task on the system.  This avoids any
stuttering that might be caused if the playback thread is delayed for
too long by other processes, which is why it's normally desirable.

But, as you've discovered, if mythfrontend crashes in such a way that
the playback thread is stuck in a tight loop, it will consume all the
CPU time and no other task will ever be allowed to run.  Since this
includes ssh and the shell, there is no way to kill the errant thread.
The only way to regain control is to reset the machine.

If you aren't experiencing any video playback problems, there is no
benefit in making the executable setuid.  On the other hand, if Myth is
working correctly, there should be no harm in making it setuid either.

p.