[PATCH bpf] selftests/bpf: Fix massive output from test_maps

* [PATCH bpf] selftests/bpf: Fix massive output from test_maps
@ 2020-08-26  8:17 Jesper Dangaard Brouer
  2020-08-26  8:29 ` Jesper Dangaard Brouer
  0 siblings, 1 reply; 3+ messages in thread
From: Jesper Dangaard Brouer @ 2020-08-26  8:17 UTC (permalink / raw)
  To: Jesper Dangaard Brouer, bpf
  Cc: Daniel Borkmann, Alexei Starovoitov, ykaliuta, zsun, vkabatov

When stdout output from the selftests tool 'test_maps' gets redirected
into e.g file or pipe, then the output lines increase a lot (from 21
to 33949 lines).  This is caused by the printf that happens before the
fork() call, and there are user-space buffered printf data that seems
to be duplicated into the forked process.

To fix this fflush() stdout before the fork loop in __run_parallel().

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
 tools/testing/selftests/bpf/test_maps.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/tools/testing/selftests/bpf/test_maps.c b/tools/testing/selftests/bpf/test_maps.c
index 754cf611723e..0d92ebcb335d 100644
--- a/tools/testing/selftests/bpf/test_maps.c
+++ b/tools/testing/selftests/bpf/test_maps.c
@@ -1274,6 +1274,8 @@ static void __run_parallel(unsigned int tasks,
 	pid_t pid[tasks];
 	int i;
 
+	fflush(stdout);
+
 	for (i = 0; i < tasks; i++) {
 		pid[i] = fork();
 		if (pid[i] == 0) {



^ permalink raw reply related	[flat|nested] 3+ messages in thread