* Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> [2020-12-14] > On 2020-12-08 23:58:27 [+0000], Orivej Desh wrote: > > With sched-Add-migrate_disable.patch first released in v5.9-rc8-rt14 [1] > > linux-rt defines functions migrate_disable and migrate_enable. > > They are used in linux headers in various macros and static inline > > functions, and in particular in kmap_atomic and kunmap_atomic. > > The latter are needed by ZFS which currently fails to build against > > 5.9-rt [2] because these functions are exported with EXPORT_SYMBOL_GPL. > > Could you export them with EXPORT_SYMBOL instead? > > This is out of my jurisdiction, so just a few notes: > - v5.9 is out of maintenance. Be careful. Thanks! I have noticed a bug with usb-storage (using smp_processor_id in preemptible code) in 5.9.1-rt20 thas has been fixed in 5.10-rt17. > - We don't export symbols for out-of-tree modules. The issue is that in the vanilla kernel these two functions are available as macros that expand into EXPORT_SYMBOL function calls (kunmap_atomic_high, etc.). If I am not mistaken the kernel is generally supposed to keep the API made available to non-GPL modules still available, for example here https://lwn.net/Articles/171838/ : "When GPL-only exports were first added to the kernel, they went in with the understanding that only new symbols would be tagged GPL-only. The current module interface - while always subject to change - was not to have symbols withdrawn arbitrarily." The current rt patch has this effect: it makes non-GPL API of the vanilla kernel GPL-only.
