Re: [PATCH RFC 09/13] arm64: ftrace: Maintain Tasks RCU trampoline nesting in ftrace_caller

[Josef Bacik <josef@toxicpanda.com>]

On Thu, 10 Sep 2026 19:04:36 +0000, sashiko-bot@kernel.org wrote:
> > +/* End of [ftrace_caller, ...) for arch_rcu_tasks_ip_in_trampoline(). */
> > +SYM_CODE_START(ftrace_static_tramp_end)
> > +SYM_CODE_END(ftrace_static_tramp_end)
> > +
> >  #else /* CONFIG_DYNAMIC_FTRACE_WITH_ARGS */
>
> [Severity: Low]
> Will this cause a linker error when compiling with
> CONFIG_RCU_TASKS_PREEMPT_QS=y but CONFIG_DYNAMIC_FTRACE_WITH_ARGS=n?

No, that configuration cannot exist. CONFIG_RCU_TASKS_PREEMPT_QS is
def_bool on ARCH_HAS_RCU_TASKS_PREEMPT_QS, and the only place arm64 sets
that is in patch 13:

	select ARCH_HAS_RCU_TASKS_PREEMPT_QS if DYNAMIC_FTRACE_WITH_ARGS

so on arm64 RCU_TASKS_PREEMPT_QS=y implies DYNAMIC_FTRACE_WITH_ARGS=y and
both the marker in entry-ftrace.S and the arch_rcu_tasks_ip_in_trampoline()
that references it are built together or not at all. At this point in the
series (patch 9) nothing selects the option yet, so the reference is not
built either.

For the tool: the two symbols are tied by a Kconfig dependency introduced
later in the same series; checking the select conditions across the
series would have avoided this one. No change for v2 beyond a note in the
changelog.

Thanks,

Josef