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SubjectRe: [RFC PATCH 1/2] PM/runtime: introduce trace points for tracing rpm_* functions
From
Hi,

On Mon, Sep 26, 2011 at 9:40 PM, Steven Rostedt <rostedt@goodmis.org> wrote:
> On Thu, 2011-09-22 at 12:11 +0800, tom.leiming@gmail.com wrote:
>> From: Ming Lei <tom.leiming@gmail.com>
>>
>> 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@gmail.com>
>> ---
>>  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.

Yes, you right, but __get_str() may introduce some extra loading, could
it be changed to below just like what dev_printk does?

__entry->name = dev ? dev_name(dev) : NULL;

>
> 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.

IMO, __func__ is better than %pS here because %pS will dump some
offset info (such as runtime_suspend+0x0/0x158), but which is
not needed in this case.( we just need to make return value to match the
previous function name, such as below)

rpm_suspend: omap_hsmmc.0 flags=9
...
rpm_return_int: rpm_suspend:omap_hsmmc.0 ret=0

>
> -- 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@gmail.com>
>> + */
>> +
>> +#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);
>> +
>
>
>


thanks,
--
Ming Lei
--
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