From: Tom Zanussi <tzanussi@gmail.com>
Date: Wed, 5 May 2010 05:27:40 +0000 (-0500)
Subject: perf/live-mode: Handle payload-less events
X-Git-Tag: v2.6.35-rc1~522^2~42^2~1
X-Git-Url: https://openfabrics.org/gitweb/?a=commitdiff_plain;h=794e43b56c18b95fc9776c914a2659e7d558a352;p=~shefty%2Frdma-dev.git

perf/live-mode: Handle payload-less events

Some events, such as the PERF_RECORD_FINISHED_ROUND event consist of
only an event header and no data.  In this case, a 0-length payload
will be read, and the 0 return value will be wrongly interpreted as an
'unexpected end of event stream'.

This patch allows for proper handling of data-less events by skipping
0-length reads.

Signed-off-by: Tom Zanussi <tzanussi@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Masami Hiramatsu <mhiramat@redhat.com>
LKML-Reference: <1273038527.6383.51.camel@tropicana>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
---

diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index 9401909fa28..00ab298bbb4 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -696,15 +696,18 @@ more:
 	p = &event;
 	p += sizeof(struct perf_event_header);
 
-	err = do_read(self->fd, p, size - sizeof(struct perf_event_header));
-	if (err <= 0) {
-		if (err == 0) {
-			pr_err("unexpected end of event stream\n");
-			goto done;
-		}
+	if (size - sizeof(struct perf_event_header)) {
+		err = do_read(self->fd, p,
+			      size - sizeof(struct perf_event_header));
+		if (err <= 0) {
+			if (err == 0) {
+				pr_err("unexpected end of event stream\n");
+				goto done;
+			}
 
-		pr_err("failed to read event data\n");
-		goto out_err;
+			pr_err("failed to read event data\n");
+			goto out_err;
+		}
 	}
 
 	if (size == 0 ||