From: tip-bot for Tom Zanussi on
Commit-ID: cbb5cf7ff6b298beacfe23db3386335b0b9c0a2d
Author: Tom Zanussi <tzanussi(a)>
AuthorDate: Tue, 4 May 2010 23:02:10 -0500
Committer: Frederic Weisbecker <fweisbec(a)>
CommitDate: Thu, 20 May 2010 08:37:17 +0200

perf: Use read() instead of lseek() in trace_event_read.c:skip()

This is a small fix for a problem affecting live-mode, introduced

root(a)tropicana:~# perf trace rwtop
perf trace started with Perl
script /root/libexec/perf-core/scripts/perl/

Fatal: did not read header event

commit d00a47cce569a3e660a8c9de5d57af28d6a9f0f7 added a skip()
function to skip over e.g. header_page, but this doesn't work for
live mode. This patch re-implements skip() to use read() instead of
lseek() to fix that.

Signed-off-by: Tom Zanussi <tzanussi(a)>
Cc: Ingo Molnar <mingo(a)>
Cc: Peter Zijlstra <a.p.zijlstra(a)>
Cc: Arnaldo Carvalho de Melo <acme(a)>
Cc: Paul Mackerras <paulus(a)>
LKML-Reference: <1273032130.6383.28.camel(a)tropicana>
Signed-off-by: Frederic Weisbecker <fweisbec(a)>
tools/perf/util/trace-event-read.c | 19 +++++++++++++------
1 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/tools/perf/util/trace-event-read.c b/tools/perf/util/trace-event-read.c
index cb54cd0..f55cc3a 100644
--- a/tools/perf/util/trace-event-read.c
+++ b/tools/perf/util/trace-event-read.c
@@ -53,12 +53,6 @@ static unsigned long page_size;
static ssize_t calc_data_size;
static bool repipe;

-/* If it fails, the next read will report it */
-static void skip(int size)
- lseek(input_fd, size, SEEK_CUR);
static int do_read(int fd, void *buf, int size)
int rsize = size;
@@ -98,6 +92,19 @@ static int read_or_die(void *data, int size)
return r;

+/* If it fails, the next read will report it */
+static void skip(int size)
+ char buf[BUFSIZ];
+ int r;
+ while (size) {
+ r = size > BUFSIZ ? BUFSIZ : size;
+ read_or_die(buf, r);
+ size -= r;
+ };
static unsigned int read4(void)
unsigned int data;
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