Generic kernels feed many operation through the "machvec" logic to get the correct form of the operation for the current system. "mmiowb()" is one of those operations.
Although machvec is initialized very early in boot, it isn't early enough for a recent upstream kernel change that added mmiowb to the spin_unlock() path.
Statically initialize the mmiowb field of machvec so that we won't die with a call through a NULL pointer. This should be safe because we do the real initialization of machvec before bringing up any addtional CPUs or doing any I/O.
Fixes: 49ca6462fc9e ("ia64/mmiowb: Add unconditional mmiowb() to arch_spin_unlock()")
8a635ffb1421 ia64: Make sure that we have a mmiowb function real early
arch/ia64/kernel/machvec.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)