linux-kernel - Re: [patch 14/41] x86/smp: Use static key for reschedule interrupt tracing

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Date:   Fri, 25 Aug 2017 17:10:10 -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 14/41] x86/smp: Use static key for reschedule interrupt
 tracing

On Fri, 25 Aug 2017 22:07:33 +0200 (CEST)
Thomas Gleixner <tglx@...utronix.de> wrote:

> Fixed up version below.
> 

Reviewed-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

-- Steve

> Thanks,
> 
> 	tglx
> 8<---------------------
> --- a/arch/x86/include/asm/hw_irq.h
> +++ b/arch/x86/include/asm/hw_irq.h
> @@ -48,7 +48,7 @@ extern asmlinkage void call_function_sin
>  
>  #ifdef CONFIG_TRACING
>  /* Interrupt handlers registered during init_IRQ */
> -extern void trace_reschedule_interrupt(void);
> +#define trace_reschedule_interrupt	reschedule_interrupt
>  #define trace_call_function_interrupt	call_function_interrupt
>  #define trace_call_function_single_interrupt	call_function_single_interrupt
>  #define trace_thermal_interrupt	thermal_interrupt
> --- a/arch/x86/kernel/smp.c
> +++ b/arch/x86/kernel/smp.c
> @@ -254,37 +254,27 @@ static void native_stop_other_cpus(int w
>  }
>  
>  /*
> - * Reschedule call back.
> + * Reschedule call back. KVM uses this interrupt to force a cpu out of
> + * guest mode
>   */
> -static inline void __smp_reschedule_interrupt(void)
> -{
> -	inc_irq_stat(irq_resched_count);
> -	scheduler_ipi();
> -}
> -
>  __visible void __irq_entry smp_reschedule_interrupt(struct pt_regs *regs)
>  {
>  	ack_APIC_irq();
> -	__smp_reschedule_interrupt();
> -	/*
> -	 * KVM uses this interrupt to force a cpu out of guest mode
> -	 */
> -}
> -
> -__visible void __irq_entry smp_trace_reschedule_interrupt(struct pt_regs *regs)
> -{
> -	/*
> -	 * Need to call irq_enter() before calling the trace point.
> -	 * __smp_reschedule_interrupt() calls irq_enter/exit() too (in
> -	 * scheduler_ipi(). This is OK, since those functions are allowed
> -	 * to nest.
> -	 */
> -	ipi_entering_ack_irq();
> -	trace_reschedule_entry(RESCHEDULE_VECTOR);
>  	inc_irq_stat(irq_resched_count);
> +
> +	if (trace_irqvectors_enabled()) {
> +		/*
> +		 * scheduler_ipi() might call irq_enter() as well, but
> +		 * nested calls are fine.
> +		 */
> +		irq_enter();
> +		trace_reschedule_entry(RESCHEDULE_VECTOR);
> +		scheduler_ipi();
> +		trace_reschedule_exit(RESCHEDULE_VECTOR);
> +		irq_exit();
> +		return;
> +	}
>  	scheduler_ipi();
> -	trace_reschedule_exit(RESCHEDULE_VECTOR);
> -	exiting_irq();
>  }
>  
>  __visible void __irq_entry smp_call_function_interrupt(struct pt_regs *regs)
>