[PATCH] selftests/nolibc: test_fork: fix up duplicated print

From: Zhangjin Wu
Date: Thu Jun 01 2023 - 22:42:08 EST


Hi, Willy

What about this one for 2023xxxx-nolibc-rv32+stkp6?

@Thomas, welcome your Reviewed-by If it is ok for you ;-)

Best regards,
Zhangjin

> running nolibc-test with glibc on x86_64 got such print issue:
>
> 29 execve_root = -1 EACCES [OK]
> 30 fork30 fork = 0 [OK]
> 31 getdents64_root = 712 [OK]
>
> The fork test case has three printf calls:
>
> (1) llen += printf("%d %s", test, #name);
> (2) llen += printf(" = %d %s ", expr, errorname(errno));
> (3) llen += pad_spc(llen, 64, "[FAIL]\n"); --> vfprintf()
>
> In the following scene, the above issue happens:
>
> (a) The parent calls (1)
> (b) The parent calls fork()
> (c) The child runs and shares the print buffer of (1)
> (d) The child exits, flushs the print buffer and closes its own stdout/stderr
> * "30 fork" is printed at the first time.
> (e) The parent calls (2) and (3), with "\n" in (3), it flushs the whole buffer
> * "30 fork = 0 ..." is printed
>
> Therefore, there are two "30 fork" in the stdout.
>
> Between (a) and (b), if flush the stdout (and the sterr), the child in
> stage (c) will not be able to 'see' the print buffer.
>
> Signed-off-by: Zhangjin Wu <falcon@xxxxxxxxxxx>
> ---
> tools/testing/selftests/nolibc/nolibc-test.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c
> index 7de46305f419..88323a60aa4a 100644
> --- a/tools/testing/selftests/nolibc/nolibc-test.c
> +++ b/tools/testing/selftests/nolibc/nolibc-test.c
> @@ -486,7 +486,13 @@ static int test_getpagesize(void)
> static int test_fork(void)
> {
> int status;
> - pid_t pid = fork();
> + pid_t pid;
> +
> + /* flush the printf buffer to avoid child flush it */
> + fflush(stdout);
> + fflush(stderr);
> +
> + pid = fork();
>
> switch (pid) {
> case -1:
> --
> 2.25.1
>
>