perf diff: Fix to work with new hists design

The perf diff command is broken since:
  perf hists: Threaded addition and sorting of entries
  commit 1980c2ebd7020d82c024b8c4046849b38e78e7da

Several places were broken:
  - hists data need to be collected into opened sessions instead
    of into events
  - session's hists data need to be initialized properly when the
    session is created
  - hist_entry__pcnt_snprintf: the percentage and displacement
    buffer preparation must not use 'ret' because it's used
    as a pointer to the final buffer

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20120322133726.GB1601@m.brq.redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index 002ebbf59f48..9412e3b05f68 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -140,6 +140,7 @@ struct perf_session *perf_session__new(const char *filename, int mode,
         INIT_LIST_HEAD(&self->ordered_samples.sample_cache);
         INIT_LIST_HEAD(&self->ordered_samples.to_free);
         machine__init(&self->host_machine, "", HOST_KERNEL_ID);
+        hists__init(&self->hists);
 
         if (mode == O_RDONLY) {
                 if (perf_session__open(self, force) < 0)