linux-kernel - Re: [RFC PATCH v2 5/8] irq_work: Trace self-IPIs sent via arch_irq_work

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Date:   Thu, 17 Nov 2022 10:10:57 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Valentin Schneider <vschneid@...hat.com>
Cc:     linux-alpha@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-snps-arc@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-csky@...r.kernel.org,
        linux-hexagon@...r.kernel.org, linux-ia64@...r.kernel.org,
        loongarch@...ts.linux.dev, linux-mips@...r.kernel.org,
        openrisc@...ts.librecores.org, linux-parisc@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-riscv@...ts.infradead.org,
        linux-s390@...r.kernel.org, linux-sh@...r.kernel.org,
        sparclinux@...r.kernel.org, linux-xtensa@...ux-xtensa.org,
        x86@...nel.org, "Paul E. McKenney" <paulmck@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Juri Lelli <juri.lelli@...hat.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>, Marc Zyngier <maz@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Russell King <linux@...linux.org.uk>,
        Nicholas Piggin <npiggin@...il.com>,
        Guo Ren <guoren@...nel.org>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [RFC PATCH v2 5/8] irq_work: Trace self-IPIs sent via
 arch_irq_work_raise()

On Wed, Nov 02, 2022 at 06:33:33PM +0000, Valentin Schneider wrote:
> IPIs sent to remove CPUs via irq_work_queue_on() are now covered by
> trace_ipi_send_cpumask(), add another instance of the tracepoint to cover
> self-IPIs.
> 
> Signed-off-by: Valentin Schneider <vschneid@...hat.com>
> ---
>  kernel/irq_work.c | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/irq_work.c b/kernel/irq_work.c
> index 7afa40fe5cc43..aec38c294ce68 100644
> --- a/kernel/irq_work.c
> +++ b/kernel/irq_work.c
> @@ -22,6 +22,8 @@
>  #include <asm/processor.h>
>  #include <linux/kasan.h>
>  
> +#include <trace/events/ipi.h>
> +
>  static DEFINE_PER_CPU(struct llist_head, raised_list);
>  static DEFINE_PER_CPU(struct llist_head, lazy_list);
>  static DEFINE_PER_CPU(struct task_struct *, irq_workd);
> @@ -74,6 +76,16 @@ void __weak arch_irq_work_raise(void)
>  	 */
>  }
>  
> +static inline void irq_work_raise(struct irq_work *work)

__always_inline, unless you want to occasionally only see it point to
__irq_work_queue_local().

> +{
> +	if (trace_ipi_send_cpumask_enabled() && arch_irq_work_has_interrupt()) {
> +		trace_ipi_send_cpumask(cpumask_of(smp_processor_id()),
> +				       _RET_IP_,
> +				       work->func);
	}
> +
> +	arch_irq_work_raise();
> +}
> +
>  /* Enqueue on current CPU, work must already be claimed and preempt disabled */
>  static void __irq_work_queue_local(struct irq_work *work)
>  {
> @@ -99,7 +111,7 @@ static void __irq_work_queue_local(struct irq_work *work)
>  
>  	/* If the work is "lazy", handle it from next tick if any */
>  	if (!lazy_work || tick_nohz_tick_stopped())
> -		arch_irq_work_raise();
> +		irq_work_raise(work);
>  }
>  
>  /* Enqueue the irq work @work on the current CPU */
> -- 
> 2.31.1
>