Re: [PATCH net] selftests: rtnetlink: try double sleep to give WQ a chance

[Hangbin Liu <liuhangbin@gmail.com>]

On Thu, Jul 10, 2025 at 07:53:12AM -0700, Jakub Kicinski wrote:
> The rtnetlink test for preferred lifetime of an address is quite flaky.
> Problems started around the 6.16 merge window in May. The test fails
> with:
> 
>    FAIL: preferred_lft addresses remaining
> 
> and unlike most of our flakes this one fails on the "normal" kernel
> builds, not the builds with kernel/configs/debug.config. I suspect
> the flakes may be related to power saving, since the expirations
> run from a "power efficient" workqueue. Adding a short sleep seems
> to decrease the flakes by 8x but they still happen. With this
> patch in place we get a flake every couple of weeks, not every
> couple of days. Better ideas welcome..
> 
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
> ---
> CC: liuhangbin@gmail.com
> CC: shuah@kernel.org
> CC: linux-kselftest@vger.kernel.org
> ---
>  tools/testing/selftests/net/rtnetlink.sh | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/tools/testing/selftests/net/rtnetlink.sh b/tools/testing/selftests/net/rtnetlink.sh
> index 2e8243a65b50..b9e1497ea27a 100755
> --- a/tools/testing/selftests/net/rtnetlink.sh
> +++ b/tools/testing/selftests/net/rtnetlink.sh
> @@ -299,6 +299,11 @@ kci_test_addrlft()
>  	done
>  
>  	sleep 5
> +	# Schedule out for a bit, address GC runs from the power efficient WQ
> +	# if the long sleep above has put the whole system into sleep state
> +	# the WQ may have not had a chance to run.
> +	sleep 0.1
> +

How about use slowwait to check if the address still exists. e.g.

check_addr_not_exist()
{
	dev=$1
	addr=$2
	if ip addr show dev $dev | grep -q $addr; then
		return 1
	else
		return 0
}

	slowwait 5 check_addr_not_exist "$devdummy" "10.23.11."

>  	run_cmd_grep_fail "10.23.11." ip addr show dev "$devdummy"
>  	if [ $? -eq 0 ]; then
>  		check_err 1
> -- 
> 2.50.0
>