#3010: Instructions to autoload wrapper modules (like snd-pcm-oss) need updating
with kmod
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Reporter: bryan@… | Owner: bryan@…
Type: defect | Status: new
Priority: normal | Milestone: 7.1
Component: Book | Version: SVN
Severity: normal | Keywords:
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Either kmod or udev go into some kind of forkbomb or almost-infinite loop
with a naive extension of our instructions. I had this in
/etc/modprobe.d/sound.conf:
install snd-pcm /sbin/modprobe -i snd-pcm ; /sbin/modprobe snd-pcm-oss ;
/sbin/modprobe snd-mixer-oss ; /sbin/modprobe snd-seq ; /bin/true
per section 7.9, and the forkbomb happened when I loaded the snd-xxxx
module for my card. (It does eventually finish, but much later than the
udev timeout, and much longer than it should ever take to load ~20
different modules in the dependency list for my sound card. The PID of
the next process to be forked is up in the 10000 range when this is hit at
boot time, as well, so at least 10k processes were forked and exited.
Possibly plus some integer multiple of 32768, since the PID ends up
wrapping around. Anyway...)
Couldn't find upstream documentation on how to do this specifically for
snd-pcm-oss, but it turns out the syntax for a usable alternative is in
kmod's modprobe.d manpage:
softdep snd-pcm post: snd-pcm-oss snd-mixer-oss snd-seq
Which works fine; no more forkbombs.
The manpage also says that eventually "install" and "remove" commands will
get deprecated (printing warnings), and then removed, and softdep is the
way to go. Seems reasonable (the only thing I ever used "install" for was
soft user-added dependencies anyway).
(Note that kmod also provides a "softdep <module> pre: <module>..."
alternative, or one with both "pre:" and "post:". Just "post:" is fine
for wrapper modules though.)
We should update chapter07/udev.xml (section 7.9) to refer people to
"softdep" instead of "install". I can throw together a change to do it,
but filing this ticket so it isn't forgotten about. (And so I can find
the method next time I need to use it, and so I can try to get Google to
show something newer than 2003 for "autoload snd-pcm-oss". Heh.)
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Ticket URL: <http://wiki.linuxfromscratch.org/lfs/ticket/3010>
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