perf util: Fix do_read() to fail on EOF instead of busy-looping

While toying with perf, I've noticed that perf record can
easily enter a busy loop when doing something as silly as:

    $ perf record -A ls

Yeah, do_read here really wants to read a known size, not being
able to should die(), not busy-loop ;)

That was the cause for the bug.

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

1 files changed, 2 insertions, 0 deletions

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index 95a44bcfc2dc..b92a457ca32e 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -185,6 +185,8 @@ static void do_read(int fd, void *buf, size_t size)
 
                 if (ret < 0)
                         die("failed to read");
+                if (ret == 0)
+                        die("failed to read: missing data");
 
                 size -= ret;
                 buf += ret;