Hello. On neděle 28. listopadu 2021 1:07:49 CET Angelo Haller wrote: > Greetings. I hope I picked the right mailing list, as this issue might > be one that affects various subsystems and components: > > When compiling kernel 5.15 (and 5.16-rc2) with `CONFIG_PREEMPT_RT` > enabled, some of the symbols being exported as `EXPORT_SYMBOL` suddenly > become `EXPORT_SYMBOL_GPL` through transitive effects. > > In particular the symbols `migrate_enable` and `migrate_disable` are > currently marked as `EXPORT_SYMBOL_GPL` - yet are called from multiple > functions that are marked as `EXPORT_SYMBOL`. > > Here an (incomplete?) listing of call sites I came across: > > kernel/locking/spinlock_rt.c - rt_spin_unlock() > kernel/locking/spinlock_rt.c - rt_read_unlock() > kernel/locking/spinlock_rt.c - rt_write_unlock() > mm/highmem.c - kunmap_local_indexed() > > The issue I'm facing in particular is kmap_atomic() calling > `migrate_disable` and therefore suddenly becoming GPL-only. This breaks > the out-of-tree CDDL licensed module ZFS and has been reported before > already [0]. The conversation seemingly going nowhere - or patches at > least not being applied upstream. Downstream issue for reference [1]. What about going the other way around and let ZFS be re-licensed under GPL? > As the original implementation of `migrate_enable` and `migrate_disable` > is apparently by Peter Zijlstra [2]. Peter would you be willing to > re-license both symbols `migrate_enable` and `migrate_disable` as > `EXPORT_SYMBOL`? > > The bigger issue I'm seeing though is that there is currently no > automated test to uncover exported symbols changing their license > depending on build configuration? I am not intimately familiar with the > API guarantees the kernel gives, but this seems like a violation. There > might be other symbols with similar licensing problems. > > I can open a bugzilla ticket too - if that is preferred. > > Angelo > > > [0] > https://lore.kernel.org/linux-rt-users/20201208212841.694b3022@orivej.orivej > .org/T/ [1] https://github.com/openzfs/zfs/issues/11097 > [2] > https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git/diff/p > atches/0009-sched-Add-migrate_disable.patch?h=v5.9-rc8-rt14-patches&id=9a89b > fdb3bc77aecdd0ff8cc69b595541c7b50c4 -- Oleksandr Natalenko (post-factum)
