Re: [PATCH bpf-next] selftests/bpf: Fix wq test by changing 50us sleep to polling over 1s

["Kumar Kartikeya Dwivedi" <memxor@gmail.com>]

On Mon Oct 5, 2026 at 11:37 AM CEST, Jonathan Bastari Thamrin via B4 Relay wrote:
> From: Jonathan Bastari Thamrin <thamrinjonathan@gmail.com>
>
> wq test fails with ok_sleepable reading 0 instead of 2 as workqueue
> callback hasn't executed before check.
>
> This happens as callback runs later on a kworker and 50us isn't always
> enough.
>
> Change from 50us sleep to polling over 1s.
>
> Before (usleep(50)): 3 fails out of 5000 runs
> Diagnosing issue (usleep(0)): 23 out of 100 runs
> After (Polling): 0 out of 5000 runs
> Tested using vmtest on x86_64, test pinned to one CPU with `yes` load
>
> Link: https://github.com/kernel-patches/vmtest/issues/455
>
> Signed-off-by: Jonathan Bastari Thamrin <thamrinjonathan@gmail.com>
> ---
>  tools/testing/selftests/bpf/prog_tests/wq.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/wq.c b/tools/testing/selftests/bpf/prog_tests/wq.c
> index 84831eecc..b55d8547f 100644
> --- a/tools/testing/selftests/bpf/prog_tests/wq.c
> +++ b/tools/testing/selftests/bpf/prog_tests/wq.c
> @@ -7,7 +7,7 @@
>  void serial_test_wq(void)
>  {
>  	struct wq *wq_skel = NULL;
> -	int err, prog_fd;
> +	int err, prog_fd, tries;
>
>  	LIBBPF_OPTS(bpf_test_run_opts, topts);
>
> @@ -28,7 +28,13 @@ void serial_test_wq(void)
>  	ASSERT_OK(err, "test_run");
>  	ASSERT_EQ(topts.retval, 0, "test_run");
>
> -	usleep(50); /* 10 usecs should be enough, but give it extra */
> +	/* loop check over 1 sec to make sure it doesn't fail early when busy */
> +	for (tries = 1000; tries >= 0; tries--) {
> +		if (wq_skel->bss->ok_sleepable == (1 << 1))
> +			break;
> +
> +		usleep(1000);
> +	}
>

Please figure out the actual condition this loop is trying to wait for and
establish it directly, there are several examples in the selftests.

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