nmi_backtrace: generate one-line reports for idle cpus

nmi_backtrace: generate one-line reports for idle cpus

When doing an nmi backtrace of many cores, most of which are idle, the
output is a little overwhelming and very uninformative.  Suppress
messages for cpus that are idling when they are interrupted and just
emit one line, "NMI backtrace for N skipped: idling at pc 0xNNN".

We do this by grouping all the cpuidle code together into a new
.cpuidle.text section, and then checking the address of the interrupted
PC to see if it lies within that section.

This commit suitably tags x86 and tile idle routines, and only adds in
the minimal framework for other architectures.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Chris Metcalf <[email protected]>
Acked-by: Peter Zijlstra (Intel) <[email protected]>
Tested-by: Peter Zijlstra (Intel) <[email protected]>
Tested-by: Daniel Thompson <[email protected]> [arm]
Tested-by: Petr Mladek <[email protected]>
Cc: Aaron Tomlin <[email protected]>
Cc: Peter Zijlstra (Intel) <[email protected]>
Cc: "Rafael J. Wysocki" <[email protected]>
Cc: Russell King <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>