Re: [PATCH][RFC] tracing/rcu: Add trace_##name##__rcuidle() static tracepoint for inside rcu_idle_exit() sections

["Paul E. McKenney" <paulmck@linux.vnet.ibm.com>]

On Mon, Feb 06, 2012 at 04:18:33PM -0500, Steven Rostedt wrote:
> As I have said, I may find a better solution than to create a
> TRACE_EVENT_IDLE(), and I believe I have :-)
> 
> A added a new static inline function that lets *any* tracepoint be used
> inside a rcu_idle_exit() section. And this also solves the problem where
> the same tracepoint may be used inside a rcu_idle_exit() section as well
> as outside of one.
> 
> I added a new tracepoint function with a "_rcuidle" extension. All
> tracepoints can be used with either the normal "trace_foobar()"
> function, or the "trace_foobar_rcuidle()" function when inside a
> rcu_idle_exit() section.
> 
> Ideally, this patch would be broken up into two commits. The first would
> change the tracepoint.h to introduce the new trace_foobar_rcuidle()
> static inline, and the second patch would change the power tracepoints
> to use this tracepoint function. For the RFC, I'm keeping it as a single
> patch.
> 
> Another nice aspect about this patch is that "static inline"s are not
> compiled into text when not used. So only the tracepoints that actually
> use the _rcuidle() version will have them defined in the actual text
> that is booted.
> 
> -- Steve

Aside from the "pre;" below needing to precede rcu_read_lock_sched_notrace()
as Josh noted, this looks reasonable to me.

							Thanx, Paul

> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
> 
> Index: linux-trace.git/include/linux/tracepoint.h
> ===================================================================
> --- linux-trace.git.orig/include/linux/tracepoint.h
> +++ linux-trace.git/include/linux/tracepoint.h
> @@ -114,7 +114,7 @@ static inline void tracepoint_synchroniz
>   * as "(void *, void)". The DECLARE_TRACE_NOARGS() will pass in just
>   * "void *data", where as the DECLARE_TRACE() will pass in "void *data, proto".
>   */
> -#define __DO_TRACE(tp, proto, args, cond)				\
> +#define __DO_TRACE(tp, proto, args, cond, pre, post)			\
>  	do {								\
>  		struct tracepoint_func *it_func_ptr;			\
>  		void *it_func;						\
> @@ -123,6 +123,7 @@ static inline void tracepoint_synchroniz
>  		if (!(cond))						\
>  			return;						\
>  		rcu_read_lock_sched_notrace();				\
> +		pre;							\
>  		it_func_ptr = rcu_dereference_sched((tp)->funcs);	\
>  		if (it_func_ptr) {					\
>  			do {						\
> @@ -132,6 +133,7 @@ static inline void tracepoint_synchroniz
>  			} while ((++it_func_ptr)->func);		\
>  		}							\
>  		rcu_read_unlock_sched_notrace();			\
> +		post;							\
>  	} while (0)
> 
>  /*
> @@ -139,7 +141,7 @@ static inline void tracepoint_synchroniz
>   * not add unwanted padding between the beginning of the section and the
>   * structure. Force alignment to the same alignment as the section start.
>   */
> -#define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args)	\
> +#define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
>  	extern struct tracepoint __tracepoint_##name;			\
>  	static inline void trace_##name(proto)				\
>  	{								\
> @@ -147,7 +149,17 @@ static inline void tracepoint_synchroniz
>  			__DO_TRACE(&__tracepoint_##name,		\
>  				TP_PROTO(data_proto),			\
>  				TP_ARGS(data_args),			\
> -				TP_CONDITION(cond));			\
> +				TP_CONDITION(cond),,);			\
> +	}								\
> +	static inline void trace_##name##_rcuidle(proto)		\
> +	{								\
> +		if (static_branch(&__tracepoint_##name.key))		\
> +			__DO_TRACE(&__tracepoint_##name,		\
> +				TP_PROTO(data_proto),			\
> +				TP_ARGS(data_args),			\
> +				TP_CONDITION(cond),			\
> +				rcu_idle_exit(),			\
> +				rcu_idle_enter());			\
>  	}								\
>  	static inline int						\
>  	register_trace_##name(void (*probe)(data_proto), void *data)	\
> @@ -190,7 +202,7 @@ static inline void tracepoint_synchroniz
>  	EXPORT_SYMBOL(__tracepoint_##name)
> 
>  #else /* !CONFIG_TRACEPOINTS */
> -#define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args)	\
> +#define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
>  	static inline void trace_##name(proto)				\
>  	{ }								\
>  	static inline int						\
> Index: linux-trace.git/arch/x86/kernel/process.c
> ===================================================================
> --- linux-trace.git.orig/arch/x86/kernel/process.c
> +++ linux-trace.git/arch/x86/kernel/process.c
> @@ -377,8 +377,8 @@ static inline int hlt_use_halt(void)
>  void default_idle(void)
>  {
>  	if (hlt_use_halt()) {
> -		trace_power_start(POWER_CSTATE, 1, smp_processor_id());
> -		trace_cpu_idle(1, smp_processor_id());
> +		trace_power_start_rcuidle(POWER_CSTATE, 1, smp_processor_id());
> +		trace_cpu_idle_rcuidle(1, smp_processor_id());
>  		current_thread_info()->status &= ~TS_POLLING;
>  		/*
>  		 * TS_POLLING-cleared state must be visible before we
> @@ -391,7 +391,7 @@ void default_idle(void)
>  		else
>  			local_irq_enable();
>  		current_thread_info()->status |= TS_POLLING;
> -		trace_power_end(smp_processor_id());
> +		trace_power_end_rcuidle(smp_processor_id());
>  		trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id());
>  	} else {
>  		local_irq_enable();
> @@ -450,8 +450,8 @@ EXPORT_SYMBOL_GPL(cpu_idle_wait);
>  static void mwait_idle(void)
>  {
>  	if (!need_resched()) {
> -		trace_power_start(POWER_CSTATE, 1, smp_processor_id());
> -		trace_cpu_idle(1, smp_processor_id());
> +		trace_power_start_rcuidle(POWER_CSTATE, 1, smp_processor_id());
> +		trace_cpu_idle_rcuidle(1, smp_processor_id());
>  		if (this_cpu_has(X86_FEATURE_CLFLUSH_MONITOR))
>  			clflush((void *)&current_thread_info()->flags);
> 
> @@ -461,8 +461,8 @@ static void mwait_idle(void)
>  			__sti_mwait(0, 0);
>  		else
>  			local_irq_enable();
> -		trace_power_end(smp_processor_id());
> -		trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id());
> +		trace_power_end_rcuidle(smp_processor_id());
> +		trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id());
>  	} else
>  		local_irq_enable();
>  }
> @@ -474,13 +474,13 @@ static void mwait_idle(void)
>   */
>  static void poll_idle(void)
>  {
> -	trace_power_start(POWER_CSTATE, 0, smp_processor_id());
> -	trace_cpu_idle(0, smp_processor_id());
> +	trace_power_start_rcuidle(POWER_CSTATE, 0, smp_processor_id());
> +	trace_cpu_idle_rcuidle(0, smp_processor_id());
>  	local_irq_enable();
>  	while (!need_resched())
>  		cpu_relax();
> -	trace_power_end(smp_processor_id());
> -	trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id());
> +	trace_power_end_rcuidle(smp_processor_id());
> +	trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id());
>  }
> 
>  /*
> 
>