The atomic functions smp_load_acquire() and smp_store_release()
were introduced in Linux 3.14. Older kernels miss the functions:
kni_fifo.h:19:2: error:
implicit declaration of function ‘smp_load_acquire’
kni_fifo.h:30:2: error:
implicit declaration of function ‘smp_store_release’
The fallback is to drop the atomic barrier, as it was before
the commit below.
Fixes: 711859cd0d07 ("kni: fix kernel FIFO synchronization")
Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
c6c36fe28a