perf evlist: Make event_copy local to mmaps

perf evlist: Make event_copy local to mmaps

I am getting segfaults *after* the time sorting of perf samples where
the event type is off the charts:

(gdb) bt
\#0  0x0807b1b2 in hists__inc_nr_events (hists=0x80a99c4, type=1163281902) at util/hist.c:1225
\#1  0x08070795 in perf_session_deliver_event (session=0x80a9b90, event=0xf7a6aff8, sample=0xffffc318, tool=0xffffc520,
    file_offset=0) at util/session.c:884
\#2  0x0806f9b9 in flush_sample_queue (s=0x80a9b90, tool=0xffffc520) at util/session.c:555
\#3  0x0806fc53 in process_finished_round (tool=0xffffc520, event=0x0, session=0x80a9b90) at util/session.c:645

This is bizarre because the event has already been processed once --
before it was added to the samples queue -- and the event was found to
be sane at that time.

There seem to be 2 causes:

1. perf_evlist__mmap_read updates the read location even though there
are outstanding references to events sitting in the mmap buffers via the
ordered samples queue.

2. There is a single evlist->event_copy for all evlist entries.
event_copy is used to handle an event wrapping at the mmap buffer
boundary.

This patch addresses the second problem - making event_copy local to
each perf_mmap. With this change my highly repeatable use case no longer
fails.

The first problem is much more complicated and will be the subject of a
future patch.

Signed-off-by: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1360098762-61827-1-git-send-email-dsahern@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>