By default, the switch_to arch function is called with the runqueue
locked. This is usually not a problem unless switch_to may need to
take the runqueue lock. This is usually due to a wake up operation in
-the context switch. See arch/ia64/include/asm/system.h for an example.
+the context switch. See arch/ia64/include/asm/switch_to.h for an example.
To request the scheduler call switch_to with the runqueue unlocked,
you must `#define __ARCH_WANT_UNLOCKED_CTXSW` in a header file