On Fri, 24 Jul 2009, Jon Masters wrote:
Hi,
You were concerned about rfkill install commands on IRC. Can you
summarize what the problem is? You indicated some possible problem with
an install command getting screwed up?
(copying the list since Alan was posting about rfkill on LKML)
Well, I'm not sure how much of the "problem" that led to the *real*
problem is actually a bug versus shortcomings in our desktop stack,
but to make a long story short, I got a bug report from a user that
his bluetooth radio is not turned on properly when the system boots.
After a bit of investigating, it seems the he needs the rfkill-input
module loaded in addition to the rfkill module, so I proposed this
install rule for /etc/modprobe.d/rfkill.conf:
install rfkill /sbin/modprobe rfkill-input ; /sbin/modprobe -i rfkill
I proposed that without testing it, as it passed the "well, it looks
correct to me" test :-) but as it turns out, it gets ugly very quickly.
I don't have any shell output handy, but stracing "modprobe rfkill"
after that shows it hanging at a waitpid (iirc), and then Ctrl-C'ing
that spawns a few hundred thousand lines (perhaps exaggerated, but you
get the point) of failure messages. The system basically crawls until
you manage to kill all the modprobe processes. The user who tested it
originally says that his kernel panic'd, but I've not been able to
reproduce that.
I guess what's happening has something to do with the fact that the
rfkill-input module depends on rfkill, so the load of rfkill-input
by the install line is triggering a load of rfkill, which triggers
the install line again, and so on. It's definitely a PEBKAC bug (as
in, the solution is "Don't do that"), but one where I guess m-i-t
should fail more gracefully. For what it's worth, this seems to
accomplish what I wanted:
install rfkill /sbin/modprobe -i rfkill ; /sbin/modprobe -i rfkill-input
-RW
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