This is a note to let you know that I've just added the patch titled selftests/bpf: Fix massive output from test_maps to the 5.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: selftests-bpf-fix-massive-output-from-test_maps.patch and it can be found in the queue-5.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 826dc3bde7bfe8b89b9490289e70ff74d8dcc47e Author: Jesper Dangaard Brouer <brouer@xxxxxxxxxx> Date: Wed Aug 26 10:17:36 2020 +0200 selftests/bpf: Fix massive output from test_maps [ Upstream commit fa4505675e093e895b7ec49a76d44f6b5ad9602e ] 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(). Fixes: 1a97cf1fe503 ("selftests/bpf: speedup test_maps") Signed-off-by: Jesper Dangaard Brouer <brouer@xxxxxxxxxx> Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx> Link: https://lore.kernel.org/bpf/159842985651.1050885.2154399297503372406.stgit@firesoul Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/tools/testing/selftests/bpf/test_maps.c b/tools/testing/selftests/bpf/test_maps.c index c812f0178b643..1c4219ceced2f 100644 --- a/tools/testing/selftests/bpf/test_maps.c +++ b/tools/testing/selftests/bpf/test_maps.c @@ -1282,6 +1282,8 @@ 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) {