Date:   Tue, 4 Oct 2022 13:08:00 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Peter Zijlstra <peterz@...radead.org>
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Subject: Re: [PATCH v2 23/44] arm,smp: Remove trace_.*_rcuidle() usage

On Mon, 19 Sept 2022 at 12:18, Peter Zijlstra <peterz@...radead.org> wrote:
>
> None of these functions should ever be ran with RCU disabled anymore.
>
> Specifically, do_handle_IPI() is only called from handle_IPI() which
> explicitly does irq_enter()/irq_exit() which ensures RCU is watching.
>
> The problem with smp_cross_call() was, per commit 7c64cc0531fa ("arm: Use
> _rcuidle for smp_cross_call() tracepoints"), that
> cpuidle_enter_state_coupled() already had RCU disabled, but that's
> long been fixed by commit 1098582a0f6c ("sched,idle,rcu: Push rcu_idle
> deeper into the idle path").
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>

FWIW:

Reviewed-by: Ulf Hansson <ulf.hansson@...aro.org>

Kind regards
Uffe

> ---
>  arch/arm/kernel/smp.c |    6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> --- a/arch/arm/kernel/smp.c
> +++ b/arch/arm/kernel/smp.c
> @@ -639,7 +639,7 @@ static void do_handle_IPI(int ipinr)
>         unsigned int cpu = smp_processor_id();
>
>         if ((unsigned)ipinr < NR_IPI)
> -               trace_ipi_entry_rcuidle(ipi_types[ipinr]);
> +               trace_ipi_entry(ipi_types[ipinr]);
>
>         switch (ipinr) {
>         case IPI_WAKEUP:
> @@ -686,7 +686,7 @@ static void do_handle_IPI(int ipinr)
>         }
>
>         if ((unsigned)ipinr < NR_IPI)
> -               trace_ipi_exit_rcuidle(ipi_types[ipinr]);
> +               trace_ipi_exit(ipi_types[ipinr]);
>  }
>
>  /* Legacy version, should go away once all irqchips have been converted */
> @@ -709,7 +709,7 @@ static irqreturn_t ipi_handler(int irq,
>
>  static void smp_cross_call(const struct cpumask *target, unsigned int ipinr)
>  {
> -       trace_ipi_raise_rcuidle(target, ipi_types[ipinr]);
> +       trace_ipi_raise(target, ipi_types[ipinr]);
>         __ipi_send_mask(ipi_desc[ipinr], target);
>  }
>
>
>
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> Virtualization@...ts.linux-foundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/virtualization

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