Re: [PATCH bpf 1/2] selftests/bpf: Fix timing-dependent assertions in task work stress test

["Alexei Starovoitov" <alexei.starovoitov@gmail.com>]

On Thu, Sep 17, 2026 at 04:08 PM Yun Lu <luyun_611@163.com> wrote:
> From: Yun Lu <luyun@kylinos.cn>
>
> task_work_run() assumes every stress run observes both scheduler
> contention and, when the delete thread is enabled, cancellation of at
> least one pending callback.
>
> Neither outcome is guaranteed. Contention is observed only when another
> scheduler selects the same one of 128 map values while its task work is
> outstanding. A valid run can therefore have no scheduling errors. This
> was reproduced with a single scheduler: more than one million callbacks
> were scheduled and completed while schedule_error remained zero.

So it was "reproduced" by changing nthreads from 16 to 1 ?
That's not a fix. With 16 threads hammering 128 entries for a second
schedule_error > 0 and callback_success < callback_scheduled are the
point of the test. They check that the -EBUSY path in
bpf_task_work_acquire_ctx() and the cancel path in
bpf_task_work_cancel_and_free() were actual
ly exercised. Without them
the stress test only checks that nothing crashed.
If the unmodified test fails somewhere, show the log.

Patch 2 is fine on its own. Send it alone against bpf-next.

pw-bot: cr