Re: [RFC PATCH 1/2] PM/runtime: introduce trace points for tracingrpm_* functions

[Steven Rostedt]

On Thu, 2011-09-22 at 12:11 +0800, tom.leiming@xxxxxxxxx wrote:
> From: Ming Lei <tom.leiming@xxxxxxxxx>
> 
> This patch introduces 3 trace points to prepare for tracing
> rpm_idle/rpm_suspend/rpm_resume functions, so we can use these
> trace points to replace the current dev_dbg().
> 
> Signed-off-by: Ming Lei <tom.leiming@xxxxxxxxx>
> ---
>  include/trace/events/rpm.h |   98 ++++++++++++++++++++++++++++++++++++++++++++
>  kernel/trace/Makefile      |    1 +
>  kernel/trace/rpm-traces.c  |   21 +++++++++
>  3 files changed, 120 insertions(+), 0 deletions(-)
>  create mode 100644 include/trace/events/rpm.h
>  create mode 100644 kernel/trace/rpm-traces.c
> 
> diff --git a/include/trace/events/rpm.h b/include/trace/events/rpm.h
> new file mode 100644
> index 0000000..ecd40bb
> --- /dev/null
> +++ b/include/trace/events/rpm.h
> @@ -0,0 +1,98 @@
> +
> +#undef TRACE_SYSTEM
> +#define TRACE_SYSTEM rpm
> +
> +#if !defined(_TRACE_RUNTIME_POWER_H) || defined(TRACE_HEADER_MULTI_READ)
> +#define _TRACE_RUNTIME_POWER_H
> +
> +#include <linux/ktime.h>
> +#include <linux/tracepoint.h>
> +#include <linux/device.h>
> +
> +/*
> + * The rpm_internal events are used for tracing some important
> + * runtime pm internal functions.
> + */
> +DECLARE_EVENT_CLASS(rpm_internal,
> +
> +	TP_PROTO(struct device *dev, int flags),
> +
> +	TP_ARGS(dev, flags),
> +
> +	TP_STRUCT__entry(
> +		__field(        const char *,   name            )
> +		__field(        int,            flags           )
> +		__field(        int ,   	usage_count	)
> +		__field(        int ,   	disable_depth   )
> +		__field(        int ,   	runtime_auto	)
> +		__field(        int ,   	request_pending	)
> +		__field(        int ,   	irq_safe	)
> +		__field(        int ,   	child_count 	)
> +	),
> +
> +	TP_fast_assign(
> +		__entry->name = dev_name(dev);

Don't use pointers, you must copy the name here. Otherwise, if the trace
is read after the device has left, you will be referencing a invalid
pointer and possible crash the kernel.

We have ways to express dynamic string fields. Use them.

> +		__entry->flags = flags;
> +		__entry->usage_count = atomic_read(
> +			&dev->power.usage_count);
> +		__entry->disable_depth = dev->power.disable_depth;
> +		__entry->runtime_auto = dev->power.runtime_auto;
> +		__entry->request_pending = dev->power.request_pending;
> +		__entry->irq_safe = dev->power.irq_safe;
> +		__entry->child_count = atomic_read(
> +			&dev->power.child_count);
> +	),
> +
> +	TP_printk("%s flags-%x cnt-%-2d dep-%-2d auto-%-1d p-%-1d"
> +			" irq-%-1d child-%d",
> +			__entry->name, __entry->flags,
> +			__entry->usage_count,
> +			__entry->disable_depth,
> +			__entry->runtime_auto,
> +			__entry->request_pending,
> +			__entry->irq_safe,
> +			__entry->child_count
> +		 )
> +);
> +DEFINE_EVENT(rpm_internal, rpm_suspend,
> +
> +	TP_PROTO(struct device *dev, int flags),
> +
> +	TP_ARGS(dev, flags)
> +);
> +DEFINE_EVENT(rpm_internal, rpm_resume,
> +
> +	TP_PROTO(struct device *dev, int flags),
> +
> +	TP_ARGS(dev, flags)
> +);
> +DEFINE_EVENT(rpm_internal, rpm_idle,
> +
> +	TP_PROTO(struct device *dev, int flags),
> +
> +	TP_ARGS(dev, flags)
> +);
> +
> +TRACE_EVENT(rpm_return_int,
> +	TP_PROTO(struct device *dev, const char *func, int ret),
> +	TP_ARGS(dev, func, ret),
> +
> +	TP_STRUCT__entry(
> +		__field(	const char *,		name		)
> +		__field(	const char *,		func		)
> +		__field(	int,			ret		)
> +	),
> +
> +	TP_fast_assign(
> +		__entry->name = dev_name(dev);

Same here.

> +		__entry->ret = ret;
> +		__entry->func = func;

And here. But as this is just __func__, you could use %pS and save the
pointer to the function. This is acceptable as kallsyms will will used
to find the function, and instead pass in __THIS_IP__ to the tracepoint.

-- Steve


> +	),
> +
> +	TP_printk("%s:%s ret=%d", __entry->func, __entry->name, __entry->ret)
> +);
> +
> +#endif /* _TRACE_RUNTIME_POWER_H */
> +
> +/* This part must be outside protection */
> +#include <trace/define_trace.h>
> diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
> index 761c510..56bdab5 100644
> --- a/kernel/trace/Makefile
> +++ b/kernel/trace/Makefile
> @@ -53,6 +53,7 @@ endif
>  obj-$(CONFIG_EVENT_TRACING) += trace_events_filter.o
>  obj-$(CONFIG_KPROBE_EVENT) += trace_kprobe.o
>  obj-$(CONFIG_TRACEPOINTS) += power-traces.o
> +obj-$(CONFIG_TRACEPOINTS) += rpm-traces.o
>  ifeq ($(CONFIG_TRACING),y)
>  obj-$(CONFIG_KGDB_KDB) += trace_kdb.o
>  endif
> diff --git a/kernel/trace/rpm-traces.c b/kernel/trace/rpm-traces.c
> new file mode 100644
> index 0000000..998949e
> --- /dev/null
> +++ b/kernel/trace/rpm-traces.c
> @@ -0,0 +1,21 @@
> +/*
> + * Power trace points
> + *
> + * Copyright (C) 2009 Ming Lei <tom.leiming@xxxxxxxxx>
> + */
> +
> +#include <linux/string.h>
> +#include <linux/types.h>
> +#include <linux/workqueue.h>
> +#include <linux/sched.h>
> +#include <linux/module.h>
> +#include <linux/usb.h>
> +
> +#define CREATE_TRACE_POINTS
> +#include <trace/events/rpm.h>
> +
> +EXPORT_TRACEPOINT_SYMBOL_GPL(rpm_return_int);
> +EXPORT_TRACEPOINT_SYMBOL_GPL(rpm_idle);
> +EXPORT_TRACEPOINT_SYMBOL_GPL(rpm_suspend);
> +EXPORT_TRACEPOINT_SYMBOL_GPL(rpm_resume);
> +


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