perf session: fix error message on failure to open perf.data
If we cannot open our data file, print strerror(errno) for a more
comprehensible error message; and only suggest 'perf record' on ENOENT.
In particular, this fixes the nonsensical advice when:
% sudo perf record sleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.009 MB perf.data (~381 samples) ]
% perf trace
failed to open file: perf.data (try 'perf record' first)
%
Cc: Ingo Molnar <mingo@elte.hu>
LPU-Reference: <20100612033615.GA24731@hexapodia.org>
Signed-off-by: Andy Isaacson <adi@hexapodia.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index 8f83a18..0564a5c 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -27,8 +27,10 @@
self->fd = open(self->filename, O_RDONLY);
if (self->fd < 0) {
- pr_err("failed to open file: %s", self->filename);
- if (!strcmp(self->filename, "perf.data"))
+ int err = errno;
+
+ pr_err("failed to open %s: %s", self->filename, strerror(err));
+ if (err == ENOENT && !strcmp(self->filename, "perf.data"))
pr_err(" (try 'perf record' first)");
pr_err("\n");
return -errno;