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

Hi Stephen,

> 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 <[email protected]>
> ---
>  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;

Even better: we can create a function to reap children and verify
if they are completed while counting them.
Then we can use TST_RETRY_FN_EXP_BACKOFF() on it.

The problem is that we are waiting a fixed amount of time (~1s) that
is not enough when system is overloaded.

Most likely, when you are calling kirk parallel execution, other tests
are overloading the system and this test fails accordingly.

Regards,
--
Andrea Cervesato
SUSE QE Automation Engineer Linux
andrea.cervesato-IBi9RG/[email protected]

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