[tip:perfcounters/urgent] perf record: Fix the -A UI for empty or non-existent perf.data

[tip-bot for Pierre Habouzit <pierre.habouzit@intersec.com>]

Commit-ID:  7e6649a1a2dd0774160dc4f8d5db762ac3678ba0
Gitweb:     http://git.kernel.org/tip/7e6649a1a2dd0774160dc4f8d5db762ac3678ba0
Author:     Pierre Habouzit <pierre.habouzit@intersec.com>
AuthorDate: Fri, 7 Aug 2009 14:16:01 +0200
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Fri, 7 Aug 2009 17:08:17 +0200

perf record: Fix the -A UI for empty or non-existent perf.data

1. Ignore the -A argument if there is no perf.data file
2. Treat an empty file like a non existent file.

Else, perf will try to read the perf.data header, and fail with
an error.

Treating an empty file like a non-existent file makes sense,
since an interupted (as in SIGKILLed) perf could leave such
files around, and you don't want to annoy the user with errors
for files with no data in it.

Signed-off-by: Pierre Habouzit <pierre.habouzit@intersec.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <1249647361-11582-3-git-send-email-pierre.habouzit@intersec.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>


---
 tools/perf/builtin-record.c |   12 ++++++++----
 1 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 6da0992..afbfb9d 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -524,10 +524,14 @@ static int __cmd_record(int argc, const char **argv)
 	signal(SIGCHLD, sig_handler);
 	signal(SIGINT, sig_handler);
 
-	if (!stat(output_name, &st) && !force && !append_file) {
-		fprintf(stderr, "Error, output file %s exists, use -A to append or -f to overwrite.\n",
-				output_name);
-		exit(-1);
+	if (!stat(output_name, &st) && st.st_size) {
+		if (!force && !append_file) {
+			fprintf(stderr, "Error, output file %s exists, use -A to append or -f to overwrite.\n",
+					output_name);
+			exit(-1);
+		}
+	} else {
+		append_file = 0;
 	}
 
 	flags = O_CREAT|O_RDWR;