[LTP] [PATCH v1] pipe13: Scale child reap window with LTP_TIMEOUT_MUL

[Stephen Bertram]

The post-close wait used a fixed 1000000 us cap on exponential backoff
(~524 ms total). Scale that cap with tst_multiply_timeout() so debug
kernels and LTP_TIMEOUT_MUL apply, fixing failures under parallel
Kirk workers without changing default behavior on non-debug systems.

Before (only with case 100):

pipe13.c:50: TINFO: Creating 100 child processes
pipe13.c:81: TINFO: pid 435007 still sleeps
...
pipe13.c:81: TINFO: pid 435300 still sleeps
pipe13.c:89: TFAIL: Closed pipe didn't wake up everyone
The list varied but sometimes up to 20 would remained asleep.

After using tst_multiply_timeout(), test passes.

The failure before would happen, when using 4 paralell workers
on a debug kernel, about 1 to 2 times when iterated 5 times.
With the addition of the function, under the same conditions,
it has not failed in 100 iterations.

Signed-off-by: Stephen Bertram <sbertram@redhat.com>
---
 testcases/kernel/syscalls/pipe/pipe13.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/testcases/kernel/syscalls/pipe/pipe13.c b/testcases/kernel/syscalls/pipe/pipe13.c
index 5d76e1f00..cf1ccbcbc 100644
--- a/testcases/kernel/syscalls/pipe/pipe13.c
+++ b/testcases/kernel/syscalls/pipe/pipe13.c
@@ -44,6 +44,7 @@ static void verify_pipe(unsigned int n)
 	int ret;
 	unsigned int i, cnt = 0, sleep_us = 1, fail = 0;
 	unsigned int child_num = tcases[n];
+	unsigned int sleep_us_cap = tst_multiply_timeout(1000) * 1000U;
 	int pid[child_num];
 
 	SAFE_PIPE(fds);
@@ -60,7 +61,7 @@ static void verify_pipe(unsigned int n)
 	SAFE_CLOSE(fds[0]);
 	SAFE_CLOSE(fds[1]);
 
-	while (cnt < child_num && sleep_us < 1000000) {
+	while (cnt < child_num && sleep_us < sleep_us_cap) {
 		ret = waitpid(-1, NULL, WNOHANG);
 		if (ret < 0)
 			tst_brk(TBROK | TERRNO, "waitpid()");
-- 
2.54.0