OpenAFK kernel module won't build with linux-rt kernel

[Andrea Bocci]

Binary package hint: openafs-modules-source

trying to build a binary module from openafs-modules-source 1.4.4-dfsg1-5 for linux-image-2.6.22-9-rt 2.5.22-9.20 (linux-headers-2.6.2-9-rt 2.6.22.9-20, actually) with

sudo module-assistant -t -l 2.6.22-9-rt build openafs-modules-source

fails with

...
  LD [M] /usr/src/modules/openafs/src/libafs/MODLOAD-2.6.22-9-rt-MP/openafs.o
  Building modules, stage 2.
  MODPOST 1 modules
FATAL: modpost: GPL-incompatible module openafs.ko uses GPL-only symbol '__rcu_read_unlock'

OpenAFS is distributed under the IBM Public License 1.0, which is incompatible with GPLv2, and I assume that the -rt kernel relies on GPL-only code, but an end-user should be allowed to build the module himself, since the GPL doesn't cover the derivative work unless it's redistributed (right?).

Building the same source module for linux-image-2.6.22-9-generic , of course, works.

[Johan Christiansen (johandc)]

This problem also appears for builds on Sparc64. It seems to come from a problem with the architecture specific system-call tables.

There is a workaround available:
go to your /usr/src/linux or whereever you have your linux-headers installed, then open scripts/mod/modpost.c and do a search for "GPL-incompatible" you will find two lines around line nr 1100 which says fatal('GPL-incompatible.....') - go on an change the word fatal to warn. Then save and close the file. Still standing in /usr/src/linux now run "make scripts" to recompile the modpost script.

This workaround enables the module to be loaded, at least for sparc64. Futhermore it does actually seem to work, i have seen no problems so far with 1.4.5 in ubntu 8.10 installed with this workaround.

[Russ Allbery (rra-debian)]

This was fixed in 1.4.7.dfsg1-1:

  * New upstream release.
    - Work around GPLing of RCU locks. (Closes: #476628)