linux-kernel - Re: [patch 11/41] x86/irqwork: Get rid of duplicated tracing interrupt code

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Message-ID: <20170825115549.3d3abb08@gandalf.local.home>
Date:   Fri, 25 Aug 2017 11:55:49 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>, Peter Anvin <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...en8.de>
Subject: Re: [patch 11/41] x86/irqwork: Get rid of duplicated tracing
 interrupt code

On Fri, 25 Aug 2017 12:31:14 +0200
Thomas Gleixner <tglx@...utronix.de> wrote:


> --- a/arch/x86/kernel/irq_work.c
> +++ b/arch/x86/kernel/irq_work.c
> @@ -11,24 +11,12 @@
>  #include <asm/trace/irq_vectors.h>
>  #include <linux/interrupt.h>
>  
> -static inline void __smp_irq_work_interrupt(void)
> -{
> -	inc_irq_stat(apic_irq_work_irqs);
> -	irq_work_run();
> -}
> -
>  __visible void __irq_entry smp_irq_work_interrupt(struct pt_regs *regs)
>  {
>  	ipi_entering_ack_irq();
> -	__smp_irq_work_interrupt();
> -	exiting_irq();
> -}
> -
> -__visible void __irq_entry smp_trace_irq_work_interrupt(struct pt_regs *regs)
> -{
> -	ipi_entering_ack_irq();
> +	inc_irq_stat(apic_irq_work_irqs);
>  	trace_irq_work_entry(IRQ_WORK_VECTOR);
> -	__smp_irq_work_interrupt();

This changes from what we use to have:

Original:

	ipi_entering_ack_irq();
	trace_irq_work_entry(IRQ_WORK_VECTOR);
	inc_irq_stat(apic_irq_work_irqs);
	irq_work_run();

Patched:

	ipi_entering_ack_irq();
	inc_irq_stat(apic_irq_work_irqs);
	trace_irq_work_entry(IRQ_WORK_VECTOR);
	irq_work_run();

Is there a reason for the swap? It's not mentioned in the change log.

Also, tracepoints can issue new irq works. I don't think that would be
a problem here, as interrupts are disabled in this path. Just wanted to
point it out.

-- Steve


> +	irq_work_run();
>  	trace_irq_work_exit(IRQ_WORK_VECTOR);
>  	exiting_irq();
>  }
>