Hi, Respin of the rest of the get_wchan() rework [1]. Given the many problems with STACKTRACE this series focuses on the newer ARCH_STACKWALK since that's a smaller set of architectures to review with a better specified interface. The idea is to piece-wise convert the rest of the architectures to ARCH_STACKWALK, but that can be done at leasure. PowerPC and ARM64 are a bit funny in that their __switch_to() is in C and ends up on the stack. For now simply mark it __sched to make it work. Mark wanted to maybe do something different, but I think this ought to get us started.
