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Date: Tue, 27 Sep 2011 08:53:28 +0800
From: Ming Lei <tom.leiming@...il.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: rjw@...k.pl, stern@...land.harvard.edu,
linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
mingo@...hat.com, fweisbec@...il.com
Subject: Re: [RFC PATCH 1/2] PM/runtime: introduce trace points for tracing
rpm_* functions
Hi,
On Mon, Sep 26, 2011 at 9:40 PM, Steven Rostedt <rostedt@...dmis.org> wrote:
> On Thu, 2011-09-22 at 12:11 +0800, tom.leiming@...il.com wrote:
>> From: Ming Lei <tom.leiming@...il.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@...il.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@...il.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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