linux-kernel - Re: [PATCH -tip] x86,trace: Add rcu_irq_enter/exit() in smp_trace_reschedule

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Message-ID: <1372433814.18733.335.camel@gandalf.local.home>
Date:	Fri, 28 Jun 2013 11:36:54 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Seiji Aguchi <seiji.aguchi@....com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"x86@...nel.org" <x86@...nel.org>, "hpa@...or.com" <hpa@...or.com>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"Paul E. McKenney" <paulmck@...ibm.com>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH -tip] x86,trace: Add rcu_irq_enter/exit() in
 smp_trace_reschedule_interrupt()

On Fri, 2013-06-28 at 15:13 +0000, Seiji Aguchi wrote:

> OK.
> So,  ack_APIC_irq() and irq_enter() are needed.
> It can be shared with smp_call_function() and smp_call_function_single() like this.
> I will update the patch.
> 
> arch/x86/kernel/smp.c |   23 ++++++++++++-----------
>  1 files changed, 12 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c
> index f4fe0b8..732b618 100644
> --- a/arch/x86/kernel/smp.c
> +++ b/arch/x86/kernel/smp.c
> @@ -265,23 +265,24 @@ void smp_reschedule_interrupt(struct pt_regs *regs)
>  	 */
>  }
>  
> -void smp_trace_reschedule_interrupt(struct pt_regs *regs)
> +static inline void smp_entering_irq(void)
>  {
>  	ack_APIC_irq();
> +	irq_enter();
> +}
> +
> +void smp_trace_reschedule_interrupt(struct pt_regs *regs)
> +{

Sure, but we should probably add a comment here to why
smp_trace_reschedule_interrupt() is different than
smp_reschedule_interrupt().

	/*
	 * 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.
	 */

-- Steve

> +	smp_entering_irq();
>  	trace_reschedule_entry(RESCHEDULE_VECTOR);
>  	__smp_reschedule_interrupt();
>  	trace_reschedule_exit(RESCHEDULE_VECTOR);
> +	exiting_irq();
>  	/*
>  	 * KVM uses this interrupt to force a cpu out of guest mode
>  	 */
>  }
>  
> -static inline void call_function_entering_irq(void)
> -{
> -	ack_APIC_irq();
> -	irq_enter();
> -}
> -
>  static inline void __smp_call_function_interrupt(void)
>  {
>  	generic_smp_call_function_interrupt();
> @@ -290,14 +291,14 @@ static inline void __smp_call_function_interrupt(void)
>  
>  void smp_call_function_interrupt(struct pt_regs *regs)
>  {
> -	call_function_entering_irq();
> +	smp_entering_irq();
>  	__smp_call_function_interrupt();
>  	exiting_irq();
>  }
>  
>  void smp_trace_call_function_interrupt(struct pt_regs *regs)
>  {
> -	call_function_entering_irq();
> +	smp_entering_irq();
>  	trace_call_function_entry(CALL_FUNCTION_VECTOR);
>  	__smp_call_function_interrupt();
>  	trace_call_function_exit(CALL_FUNCTION_VECTOR);
> @@ -312,14 +313,14 @@ static inline void __smp_call_function_single_interrupt(void)
>  
>  void smp_call_function_single_interrupt(struct pt_regs *regs)
>  {
> -	call_function_entering_irq();
> +	smp_entering_irq();
>  	__smp_call_function_single_interrupt();
>  	exiting_irq();
>  }
>  
>  void smp_trace_call_function_single_interrupt(struct pt_regs *regs)
>  {
> -	call_function_entering_irq();
> +	smp_entering_irq();
>  	trace_call_function_single_entry(CALL_FUNCTION_SINGLE_VECTOR);
>  	__smp_call_function_single_interrupt();
>  	trace_call_function_single_exit(CALL_FUNCTION_SINGLE_VECTOR);


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