[PATCH] perf session: Fix infinite loop on invalid perf.data file

[Namhyung Kim]

From: Namhyung Kim <namhyung.kim@xxxxxxx>

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.

Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Sonny Rao <sonnyrao@xxxxxxxxxxxx>
Signed-off-by: David Ahern <dsahern@xxxxxxxxx>
Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
---
 tools/perf/util/header.c  | 9 +++++++++
 tools/perf/util/session.c | 2 +-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index 26441d0e571b..cedccde6a6b2 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -2753,6 +2753,15 @@ 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("Data size is 0. Was the record command properly terminated?\n");
+
 	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 6c1d4447c5b4..7bbd60c0a0ed 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -1323,7 +1323,7 @@ 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;
-- 
1.7.11.7

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