nmi: provide the option to issue an NMI back trace to every cpu but current

nmi: provide the option to issue an NMI back trace to every cpu but current

Sometimes it is preferred not to use the trigger_all_cpu_backtrace()
routine when one wants to avoid capturing a back trace for current.  For
instance if one was previously captured recently.

This patch provides a new routine namely
trigger_allbutself_cpu_backtrace() which offers the flexibility to issue
an NMI to every cpu but current and capture a back trace accordingly.

Patch x86 and sparc to support new routine.

[[email protected]: add stub in #else clause]
[[email protected]: don't print message in single processor case, wrap with get/put_cpu based on Oleg's suggestion]
[[email protected]: undo C99ism]
Signed-off-by: Aaron Tomlin <[email protected]>
Signed-off-by: Don Zickus <[email protected]>
Acked-by: David S. Miller <[email protected]>
Cc: Mateusz Guzik <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Signed-off-by: Stephen Rothwell <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>