Reverting rmmod->modprobe change in bumblebee/3.2.1-8 (was: Re: Bumblebee functionality broken by the last update made by Vincent Cheng on 26-July-2015 - please react as fast as possible)

[Peter Wu]

On Fri, Aug 07, 2015 at 12:56:25PM +0100, Luca Boccassi wrote:
> On Fri, 2015-08-07 at 11:39 +0200, Peter Wu wrote:
> > Hi Luca,
> > 
> > I just did some tests with a Ubuntu 14.04 VM:
> > 
> >     sudo rm /lib/modules/`uname -r`/kernel/drivers/char/lp.ko
> >     sudo depmod
> > 
> > This simulates a mismatch between the kernel module and its file name.
> > For testing, I use the following mapping between module names and files:
> >     lsmod name  | filename  | simulates
> >     lp          | crc7.ko   | nvidia/nvidia-current.ko
> >     ppdev       | ppdev.ko  | nvidia-uvm/nvidia-uvm.ko
> > 
> > Then, I tried the following modprobe conffiles and commands:
> > 
> >  - alias nvidia nvidia-current
> >    modprobe -vr nvidia
> >    No effect!
> >  - alias nvidia nvidia-current
> >    modprobe -v nvidia
> >    Loads nividia-current.ko
> >  - remove nvidia nvidia-uvm nvidia-current
> >    modprobe -vr nvidia
> >    Works, but the exit code is always 1 if one of the modules failed to
> >    unload.
> > 
> > Why does Debian not have this issue while Ubuntu does? Debian uses the
> > last option[0], Ubuntu apparently does not. I suggest to keep the Debian
> > packaging as is because it fixes a real issue (nvidia-uvm should be
> > unloaded first) and instead modify the Ubuntu packages.
> > 
> > Since Ubuntu has so many nvidia versions, should it be put in the
> > bumblebee package (since that is the only user for now) or should it be
> > addressed in each nvidia package? (Tested it, only the first 'remove'
> > command will be used in presence of duplicate lines.)
> > 
> > Kind regards,
> > Peter
> > 
> >  [0]: https://sources.debian.net/src/nvidia-graphics-drivers/340.76-3/debian/nvidia-modprobe.conf.in/
> 
> Hi Peter,
> 
> Thanks for doing this test.
> 
> As you correctly pointed out, the reason Debian does not have the
> problem is because it uses the last method in the modprobe config file.
> Although it exits 1 (on the list to find a solution for that), both
> modules are correctly removed if present.

Bumblebee internally ignores the exit code, it only checks whether the
module is gone from /proc/modules. That's why the exit code does not
matter.

> I do not know yet if there is the same problem with nvidia-uvm on
> Ubuntu, nor what is the proper solution for Ubuntu, I plan to
> investigate later tonight or tomorrow.

Ubuntu should be the same in this regard, adding the modprobe conf file
should be sufficient. What has to be decided is whether the nvidia
packaging should apply this (I am in favor of that) or the bumblebee
packaging.

For the PPA however, I think the best course is to add the modprobe
conffile since older versions of Ubuntu will probably not get their
drivers updated for this external issue.
-- 
Kind regards,
Peter Wu
https://lekensteyn.nl
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