perf session: Fix infinite loop on invalid perf.data file

perf-record updates the header in the perf.data file at termination.
Without this update perf-report (and other processing built-ins) it
caused an infinite loop when perf report (or something like) called.

This is because the algorithm in __perf_session__process_events()
depends on the data_size which is read from file header.  Use file size
directly instead in this case to do the best-effort processing.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: David Ahern <dsahern@gmail.com>
Tested-by: Sonny Rao <sonnyrao@chromium.org>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Sonny Rao <sonnyrao@chromium.org>
Link: http://lkml.kernel.org/r/1380529188-27193-1-git-send-email-namhyung@kernel.org
Signed-off-by: David Ahern <dsahern@gmail.com>
[ Reworded warning as per Ingo Molnar suggestion, replaces 'perf.data'
  with session->filename, to precisely identify the data file involved ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

2 files changed, 13 insertions, 1 deletions

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index ce69901176d8..c3e5a3b817ab 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -2768,6 +2768,18 @@ int perf_session__read_header(struct perf_session *session)
         if (perf_file_header__read(&f_header, header, fd) < 0)
                 return -EINVAL;
 
+        /*
+         * Sanity check that perf.data was written cleanly; data size is
+         * initialized to 0 and updated only if the on_exit function is run.
+         * If data size is still 0 then the file contains only partial
+         * information.  Just warn user and process it as much as it can.
+         */
+        if (f_header.data.size == 0) {
+                pr_warning("WARNING: The %s file's data size field is 0 which is unexpected.\n"
+                           "Was the 'perf record' command properly terminated?\n",
+                           session->filename);
+        }
+
         nr_attrs = f_header.attrs.size / f_header.attr_size;
         lseek(fd, f_header.attrs.offset, SEEK_SET);
 
diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index 37c4718f6be1..568b750c01f6 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -1312,7 +1312,7 @@ int __perf_session__process_events(struct perf_session *session,
         file_offset = page_offset;
         head = data_offset - page_offset;
 
-        if (data_offset + data_size < file_size)
+        if (data_size && (data_offset + data_size < file_size))
                 file_size = data_offset + data_size;
 
         progress_next = file_size / 16;