From ed495f0945e732c55bb8c21e660c2c86f5e57812 Mon Sep 17 00:00:00 2001 From: Zhangjin Wu Date: Tue, 30 May 2023 14:03:33 +0800 Subject: selftests/nolibc: test_fork: fix up duplicated print MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Reviewed-by: Thomas Weißschuh Signed-off-by: Willy Tarreau Signed-off-by: Paul E. McKenney --- tools/testing/selftests/nolibc/nolibc-test.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) (limited to 'tools') diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c index d417ca5d976f..fa18e7dc35c8 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: -- cgit