parisc: ensure broadcast tlb purge runs single threaded

commit e82a3b75127188f20c7780bec580e148beb29da7 upstream

parisc: ensure broadcast tlb purge runs single threaded
The TLB flushing functions on hppa, which causes PxTLB broadcasts on the system
bus, needs to be protected by irq-safe spinlocks to avoid irq handlers to deadlock
the kernel. The deadlocks only happened during I/O intensive loads and triggered
pretty seldom, which is why this bug went so long unnoticed.

Signed-off-by: Helge Deller <deller@gmx.de>
[edited to use spin_lock_irqsave on UP as well since we'd been locking there
  all this time anyway, --kyle]
Signed-off-by: Kyle McMartin <kyle@mcmartin.ca>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>