Tools: properly handle the keyboard interrupt

[jeromemarchand]

Many tools rely on the user to type Ctrl-C to end, but don't actually
catch the keyboard interrupt and thus show an ugly backtrace when it
happens. Let's catch the interrupt.

[palmtenor]

[buildbot, ok to test]

[yonghong-song]

Could you share the ugly backtrace you have seen? I am curious what it is.
It would be interesting to know in what situations you could see these kinds of backtraces.

I have seen situations where there are so many events (e.g., through trace.py tracing t:raw_syscall:sys_enter), it seems stuck inside the loop in function perf_reader_event_read()
and Ctrl-C even fails and I have to do Ctrl-Z. I guess this is probably different from your situation.
I tried a few applications it seems all generate sane tracebacks.

[jeromemarchand]

By ugly backtrace, I mean any backtrace. The backtraces don't show anything wrong and the program usually exit right away (the only exception I've seen is in funcslower where I often need to hit Ctrl-C several times to quit - but that's another story). It just that users don't like to see error message when they quit a program.

[yonghong-song]

Yes. We may have a few other places, e.g., trace.py, we also need to add this change. But this can be done separately.