linux-kernel - Re: [PATCH] trace: Add special x86 irq entry/exit tracepoints

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Date:	Fri, 29 Apr 2011 02:14:30 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Vaibhav Nagarnaik <vnagarnaik@...gle.com>
cc:	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...hat.com>,
	Michael Rubin <mrubin@...gle.com>,
	David Sharp <dhsharp@...gle.com>, linux-kernel@...r.kernel.org,
	x86@...nel.org, Jiaying Zhang <jiayingz@...gle.com>
Subject: Re: [PATCH] trace: Add special x86 irq entry/exit tracepoints

On Fri, 22 Apr 2011, Vaibhav Nagarnaik wrote:
>  #include <asm/perf_event.h>
>  #include <asm/x86_init.h>
> @@ -857,7 +858,9 @@ void __irq_entry smp_apic_timer_interrupt(struct pt_regs *regs)
>  	 */
>  	exit_idle();
>  	irq_enter();
> +	trace_special_irq_entry(LOCAL_TIMER_VECTOR);

Gah. trace_special_irq is the worst name you could come up with. It's
tracing a vector which is nothing special and nothing x86 specific.

>  #include <asm/vsyscall.h>
>  #include <asm/x86_init.h>
> @@ -26,6 +27,8 @@
>  volatile unsigned long __jiffies __section_jiffies = INITIAL_JIFFIES;
>  #endif
>  
> +static struct irqaction *irq0_action;
> +

Ouch! You need an extra pointer for that ? Moving the stupid irq0
struct up a few lines would do the trick as well, right ?

> --- a/include/trace/events/irq.h
> +++ b/include/trace/events/irq.h
> @@ -139,6 +139,74 @@ DEFINE_EVENT(softirq, softirq_raise,
>  	TP_ARGS(vec_nr)
>  );
>  
> +#ifdef CONFIG_X86
> +#include <asm/irq_vectors.h>
> +#define special_irq_name(sirq) { sirq, #sirq }
> +#define show_special_irq_name(val)					\
> +	__print_symbolic(val,						\
> +			 special_irq_name(NMI_VECTOR),			\
> +			 special_irq_name(LOCAL_TIMER_VECTOR),		\
> +			 special_irq_name(ERROR_APIC_VECTOR),		\
> +			 special_irq_name(RESCHEDULE_VECTOR),		\
> +			 special_irq_name(CALL_FUNCTION_VECTOR),	\
> +			 special_irq_name(CALL_FUNCTION_SINGLE_VECTOR),	\
> +			 special_irq_name(THERMAL_APIC_VECTOR),		\
> +			 special_irq_name(THRESHOLD_APIC_VECTOR),	\
> +			 special_irq_name(REBOOT_VECTOR),		\
> +			 special_irq_name(SPURIOUS_APIC_VECTOR),	\
> +			 special_irq_name(IRQ_WORK_VECTOR),		\
> +			 special_irq_name(X86_PLATFORM_IPI_VECTOR)	\
> +			)
> +
> +#define IS_INVALIDATE_TLB_VECTOR(__irq) (\
> +		__irq >= INVALIDATE_TLB_VECTOR_START && \
> +		__irq <= INVALIDATE_TLB_VECTOR_END)

No way, really.

Interrupt vectors are not x86 specific and they do no need any
architecture specific handling at all. 

The symbolic printout is a nice to have extra, but it can be solved by
providing an arch specific lookup table which does not require any of
that #ifdef X86 mess. If the table does not exist, then you simply can
print the vector number and be done with it.

Thanks,

	tglx
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