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SubjectRe: [WARNING] kernel/rcu/tree.c:1058 rcu_irq_enter+0x15/0x20
On Wed, 30 Sep 2020 20:13:23 +0200
Peter Zijlstra <peterz@infradead.org> wrote:

> diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
> > index 6a584b3e5c74..3e5bc1dd71c6 100644
> > --- a/include/linux/lockdep.h
> > +++ b/include/linux/lockdep.h
> > @@ -550,7 +550,8 @@ do { \
> >
> > #define lockdep_assert_irqs_disabled() \
> > do { \
> > - WARN_ON_ONCE(debug_locks && raw_cpu_read(hardirqs_enabled)); \
> > + WARN_ON_ONCE(debug_locks && raw_cpu_read(hardirqs_enabled) && \
> > + likely(!(current->lockdep_recursion & LOCKDEP_RECURSION_MASK)));\
> > } while (0)
>
> Blergh, IIRC there's header hell that way. The sane fix is killing off
> that trace_*_rcuidle() disease.

Really?

I could run this through all my other tests to see if that is the case.
That is, to see if it stumbles across header hell.

>
> But I think this will also cure it.
>
> ---
> diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c
> index 6a339ce328e0..4f90293d170b 100644
> --- a/arch/x86/kernel/unwind_orc.c
> +++ b/arch/x86/kernel/unwind_orc.c
> @@ -432,7 +432,7 @@ bool unwind_next_frame(struct unwind_state *state)
> return false;
>
> /* Don't let modules unload while we're reading their ORC data. */
> - preempt_disable();
> + preempt_disable_notrace();
>
> /* End-of-stack check for user tasks: */
> if (state->regs && user_mode(state->regs))
> @@ -612,14 +612,14 @@ bool unwind_next_frame(struct unwind_state *state)
> goto err;
> }
>
> - preempt_enable();
> + preempt_enable_notrace();
> return true;
>
> err:
> state->error = true;
>
> the_end:
> - preempt_enable();
> + preempt_enable_notrace();
> state->stack_info.type = STACK_TYPE_UNKNOWN;
> return false;
> }

I think you are going to play whack-a-mole with this approach. This will
happen anytime preempt_disable is being traced within lockdep internal code.

I just hit this:

register_lock_class
assign_lock_key
__is_module_percpu_address
preempt_disable
trace_preempt_disable
rcu_irq_enter_irqson
[..]


Same thing, different path.

-- Steve

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