[tip:perf/urgent] perf kvm stat live: Enable events copying

[tip-bot for Alexander Yarygin]

Commit-ID:  673d659f5c5918b7ddbafebf1f129c9eb82973b4
Gitweb:     http://git.kernel.org/tip/673d659f5c5918b7ddbafebf1f129c9eb82973b4
Author:     Alexander Yarygin <yarygin@xxxxxxxxxxxxxxxxxx>
AuthorDate: Fri, 3 Oct 2014 18:40:12 +0400
Committer:  Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Wed, 15 Oct 2014 17:39:03 -0300

perf kvm stat live: Enable events copying

Process of analyzing events caused by 2 functions: mmap_read() and
finished_round().

During mmap_read(), perf receives events from shared memory, queues
their pointers for further processing in finished_round() and notifies
the kernel that the events have been processed.

By the time when finished_round() is invoked, queued events can be
overwritten by the kernel, so the finished_round() occurs on potentially
corrupted memory.

Since there is no place where the event can be safely consumed, let's
copy events when queueing.

Signed-off-by: Alexander Yarygin <yarygin@xxxxxxxxxxxxxxxxxx>
Cc: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Namhyung Kim <namhyung.kim@xxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Stephane Eranian <eranian@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/1412347212-28237-3-git-send-email-yarygin@xxxxxxxxxxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 tools/perf/builtin-kvm.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/perf/builtin-kvm.c b/tools/perf/builtin-kvm.c
index ef9fc15..b65eb050 100644
--- a/tools/perf/builtin-kvm.c
+++ b/tools/perf/builtin-kvm.c
@@ -1358,6 +1358,7 @@ static int kvm_events_live(struct perf_kvm_stat *kvm,
 	}
 	kvm->session->evlist = kvm->evlist;
 	perf_session__set_id_hdr_size(kvm->session);
+	ordered_events__set_copy_on_queue(&kvm->session->ordered_events, true);
 	machine__synthesize_threads(&kvm->session->machines.host, &kvm->opts.target,
 				    kvm->evlist->threads, false);
 	err = kvm_live_open_events(kvm);
--
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