On 11/12/13, 8:34 AM, Peter Zijlstra wrote:
On Tue, Nov 12, 2013 at 08:25:02AM -0700, David Ahern wrote:
The patch in this thread deletes the file. Another option is to rewind the
file to the last known good write (ie., length after last successful call to
write_output).
I'd report a warning and continue with all events that you could read
upto that point.
Coming back to this: the answer to that statement is known. The attached
patch attempt to rewind to the last good write. Subsequent reads to the
file fail with:
WARNING: The /tmp/mnt/perf.data file's data size field is 0 which is
unexpected.
Was the 'perf record' command properly terminated?
reading input file (size expected=3 received=-1)broken or missing trace data
incompatible file format (rerun with -v to learn more)
Given that it would seem deleting the file is the best option.
David
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 65615a8bc25e..309f590cf267 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -99,7 +99,22 @@ static int do_write_output(struct perf_record *rec, void
*buf, size_t size)
static int write_output(struct perf_record *rec, void *buf, size_t size)
{
- return do_write_output(rec, buf, size);
+ off_t len;
+ int rc;
+
+ /* save current length */
+ len = rec->session->header.data_offset + rec->bytes_written;
+
+ rc = do_write_output(rec, buf, size);
+
+ /* on failure reset file to last known good length */
+ if (rc < 0) {
+ pr_debug("truncating file to last known good write: len %ld\n",
len);
+ if (ftruncate(rec->file.fd, len) != 0)
+ pr_err("Double failure -- write failed and then
ftruncate\n");
+ }
+
+ return rc;
}
static int process_synthesized_event(struct perf_tool *tool,
