Re: [PATCH v4] ftrace: add a tracepoint for __raise_softirq_irqoff()

Mathieu Desnoyers
2009-05-14T12:40:29Z

* Xiao Guangrong (xiaoguangrong@cn.fujitsu.com) wrote:
> From: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
>
> This patch is modified from Mathieu Desnoyers' patch. The original patch
> can be found here:
> http://marc.info/?l=linux-kernel&m=123791201816245&w=2
> This tracepoint can trace the time stamp when softirq action is raised.
>
> Changelog for v1 -> v2:
> 1: Use TRACE_EVENT instead of DEFINE_TRACE
> 2: Move the tracepoint from raise_softirq_irqoff() to
> __raise_softirq_irqoff()
>
> Changelog for v2 -> v3:
> Move the definition of __raise_softifq_irqoff() to .c file when
> CONFIG_TRACEPOINTS is enabled, to avoid recursive includes
>
> Changelog for v3 -> v4:
> 1: Come back to v2, and use forward declarations to avoid
> recursive includes as Mathieu's suggestion
> 2: Modifiy the tracepoint name
> 3: Add comments for this tracepoint
>

This is a step in the right direction, but please see my email to Lai
about the fact that this assumes correct and undocumented include
dependencies in kernel/trace/events.c. Not explicitely stating the
include dependencies is a build error waiting to happen.

Including interrupt.h under a ifdef would allow keeping track of
TRACE_EVENT specific build dependencies neatly on a per header basis.

Mathieu

> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
> Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
> Review-by: Lai Jiangshan <laijs@cn.fujitsu.com>
> ---
> include/linux/interrupt.h | 9 ++++++++-
> include/trace/events/irq.h | 27 ++++++++++++++++++++++++++-
> 2 files changed, 34 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
> index dd574d5..51e7909 100644
> --- a/include/linux/interrupt.h
> +++ b/include/linux/interrupt.h
> @@ -18,6 +18,7 @@
> #include <asm/atomic.h>
> #include <asm/ptrace.h>
> #include <asm/system.h>
> +#include <trace/events/irq.h>
>
> /*
> * These correspond to the IORESOURCE_IRQ_* defines in
> @@ -361,7 +362,13 @@ asmlinkage void do_softirq(void);
> asmlinkage void __do_softirq(void);
> extern void open_softirq(int nr, void (*action)(struct softirq_action *));
> extern void softirq_init(void);
> -#define __raise_softirq_irqoff(nr) do { or_softirq_pending(1UL << (nr)); } while (0)
> +
> +static inline void __raise_softirq_irqoff(unsigned int nr)
> +{
> + trace_softirq_raise(nr);
> + or_softirq_pending(1UL << nr);
> +}
> +
> extern void raise_softirq_irqoff(unsigned int nr);
> extern void raise_softirq(unsigned int nr);
> extern void wakeup_softirqd(void);
> diff --git a/include/trace/events/irq.h b/include/trace/events/irq.h
> index 32a9f7e..08fa63b 100644
> --- a/include/trace/events/irq.h
> +++ b/include/trace/events/irq.h
> @@ -2,11 +2,13 @@
> #define _TRACE_IRQ_H
>
> #include <linux/tracepoint.h>
> -#include <linux/interrupt.h>
>
> #undef TRACE_SYSTEM
> #define TRACE_SYSTEM irq
>
> +struct irqaction;
> +struct softirq_action;
> +
> /**
> * irq_handler_entry - called immediately before the irq action handler
> * @irq: irq number
> @@ -128,6 +130,29 @@ TRACE_EVENT(softirq_exit,
> TP_printk("softirq=%d action=%s", __entry->vec, __get_str(name))
> );
>
> +/**
> + * softirq_raise - called immediately when a softirq is raised
> + * @nr: softirq vector number
> + */
> +TRACE_EVENT(softirq_raise,
> +
> + TP_PROTO(unsigned int nr),
> +
> + TP_ARGS(nr),
> +
> + TP_STRUCT__entry(
> + __field( unsigned int, nr )
> + __string( name, softirq_to_name[nr] )
> + ),
> +
> + TP_fast_assign(
> + __entry->nr = nr;
> + __assign_str(name, softirq_to_name[nr]);
> + ),
> +
> + TP_printk("softirq=%u action=%s", __entry->nr, __get_str(name))
> +);
> +
> #endif /* _TRACE_IRQ_H */
>
> /* This part must be outside protection */
> --
> 1.6.1.2
>
>

--
Mathieu Desnoyers
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