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Date:   Tue, 26 Mar 2019 08:18:15 -0700
From:   "Paul E. McKenney" <paulmck@...ux.ibm.com>
To:     Yafang Shao <laoar.shao@...il.com>
Cc:     rostedt@...dmis.org, mingo@...hat.com, peterz@...radead.org,
        josh@...htriplett.org, mathieu.desnoyers@...icios.com,
        jiangshanlai@...il.com, joel@...lfernandes.org,
        linux-kernel@...r.kernel.org, shaoyafang@...iglobal.com
Subject: Re: [PATCH v2 3/3] rcu: validate arguments for rcu tracepoints

On Tue, Mar 26, 2019 at 08:13:11PM +0800, Yafang Shao wrote:
> When CONFIG_RCU_TRACE is not set, all these tracepoints are defined as
> do-nothing macro.
> We'd better make those inline functions that take proper arguments.
> 
> As RCU_TRACE() is defined as do-nothing marco as well when
> CONFIG_RCU_TRACE is not set, so we can clean it up.

How about this for the commit log?

	Unless the CONFIG_RCU_TRACE kconfig option is set, almost all
	of RCU's tracepoints are defined as empty macros.  It would
	be better if these tracepoints could instead be empty inline
	functions with proper arguments and type checking.  It would
	also be good to get rid of the RCU_TRACE() macro, which
	compiles its argument in CONFIG_RCU_TRACE=y kernels and
	omits them otherwise.

	This commit therefore creates a TRACE_EVENT_RCU macro that
	is defined as TRACE_EVENT in CONFIG_RCU_TRACE=y kernels and
	as the new TRACE_EVENT_NOP otherwise, which allows the
	empty macros and the RCU_TRACE() macro to be eliminated.

With that:

Reviewed-by: Paul E. McKenney <paulmck@...ux.ibm.com>

> Signed-off-by: Yafang Shao <laoar.shao@...il.com>
> ---
>  include/trace/events/rcu.h | 81 ++++++++++++++--------------------------------
>  kernel/rcu/rcu.h           |  9 ++----
>  kernel/rcu/tree.c          |  8 ++---
>  3 files changed, 31 insertions(+), 67 deletions(-)
> 
> diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h
> index f0c4d10..e3f357b 100644
> --- a/include/trace/events/rcu.h
> +++ b/include/trace/events/rcu.h
> @@ -7,6 +7,12 @@
>  
>  #include <linux/tracepoint.h>
>  
> +#ifdef CONFIG_RCU_TRACE
> +#define TRACE_EVENT_RCU TRACE_EVENT
> +#else
> +#define TRACE_EVENT_RCU TRACE_EVENT_NOP
> +#endif
> +
>  /*
>   * Tracepoint for start/end markers used for utilization calculations.
>   * By convention, the string is of the following forms:
> @@ -35,8 +41,6 @@
>  	TP_printk("%s", __entry->s)
>  );
>  
> -#ifdef CONFIG_RCU_TRACE
> -
>  #if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU)
>  
>  /*
> @@ -62,7 +66,7 @@
>   *	"end": End a grace period.
>   *	"cpuend": CPU first notices a grace-period end.
>   */
> -TRACE_EVENT(rcu_grace_period,
> +TRACE_EVENT_RCU(rcu_grace_period,
>  
>  	TP_PROTO(const char *rcuname, unsigned long gp_seq, const char *gpevent),
>  
> @@ -101,7 +105,7 @@
>   * "Cleanup": Clean up rcu_node structure after previous GP.
>   * "CleanupMore": Clean up, and another GP is needed.
>   */
> -TRACE_EVENT(rcu_future_grace_period,
> +TRACE_EVENT_RCU(rcu_future_grace_period,
>  
>  	TP_PROTO(const char *rcuname, unsigned long gp_seq,
>  		 unsigned long gp_seq_req, u8 level, int grplo, int grphi,
> @@ -141,7 +145,7 @@
>   * rcu_node structure, and the mask of CPUs that will be waited for.
>   * All but the type of RCU are extracted from the rcu_node structure.
>   */
> -TRACE_EVENT(rcu_grace_period_init,
> +TRACE_EVENT_RCU(rcu_grace_period_init,
>  
>  	TP_PROTO(const char *rcuname, unsigned long gp_seq, u8 level,
>  		 int grplo, int grphi, unsigned long qsmask),
> @@ -186,7 +190,7 @@
>   *	"endwake": Woke piggybackers up.
>   *	"done": Someone else did the expedited grace period for us.
>   */
> -TRACE_EVENT(rcu_exp_grace_period,
> +TRACE_EVENT_RCU(rcu_exp_grace_period,
>  
>  	TP_PROTO(const char *rcuname, unsigned long gpseq, const char *gpevent),
>  
> @@ -218,7 +222,7 @@
>   *	"nxtlvl": Advance to next level of rcu_node funnel
>   *	"wait": Wait for someone else to do expedited GP
>   */
> -TRACE_EVENT(rcu_exp_funnel_lock,
> +TRACE_EVENT_RCU(rcu_exp_funnel_lock,
>  
>  	TP_PROTO(const char *rcuname, u8 level, int grplo, int grphi,
>  		 const char *gpevent),
> @@ -269,7 +273,7 @@
>   *	"WaitQueue": Enqueue partially done, timed wait for it to complete.
>   *	"WokeQueue": Partial enqueue now complete.
>   */
> -TRACE_EVENT(rcu_nocb_wake,
> +TRACE_EVENT_RCU(rcu_nocb_wake,
>  
>  	TP_PROTO(const char *rcuname, int cpu, const char *reason),
>  
> @@ -297,7 +301,7 @@
>   * include SRCU), the grace-period number that the task is blocking
>   * (the current or the next), and the task's PID.
>   */
> -TRACE_EVENT(rcu_preempt_task,
> +TRACE_EVENT_RCU(rcu_preempt_task,
>  
>  	TP_PROTO(const char *rcuname, int pid, unsigned long gp_seq),
>  
> @@ -324,7 +328,7 @@
>   * read-side critical section exiting that critical section.  Track the
>   * type of RCU (which one day might include SRCU) and the task's PID.
>   */
> -TRACE_EVENT(rcu_unlock_preempted_task,
> +TRACE_EVENT_RCU(rcu_unlock_preempted_task,
>  
>  	TP_PROTO(const char *rcuname, unsigned long gp_seq, int pid),
>  
> @@ -353,7 +357,7 @@
>   * whether there are any blocked tasks blocking the current grace period.
>   * All but the type of RCU are extracted from the rcu_node structure.
>   */
> -TRACE_EVENT(rcu_quiescent_state_report,
> +TRACE_EVENT_RCU(rcu_quiescent_state_report,
>  
>  	TP_PROTO(const char *rcuname, unsigned long gp_seq,
>  		 unsigned long mask, unsigned long qsmask,
> @@ -396,7 +400,7 @@
>   * state, which can be "dti" for dyntick-idle mode or "kick" when kicking
>   * a CPU that has been in dyntick-idle mode for too long.
>   */
> -TRACE_EVENT(rcu_fqs,
> +TRACE_EVENT_RCU(rcu_fqs,
>  
>  	TP_PROTO(const char *rcuname, unsigned long gp_seq, int cpu, const char *qsevent),
>  
> @@ -436,7 +440,7 @@
>   * events use two separate counters, and that the "++=" and "--=" events
>   * for irq/NMI will change the counter by two, otherwise by one.
>   */
> -TRACE_EVENT(rcu_dyntick,
> +TRACE_EVENT_RCU(rcu_dyntick,
>  
>  	TP_PROTO(const char *polarity, long oldnesting, long newnesting, atomic_t dynticks),
>  
> @@ -468,7 +472,7 @@
>   * number of lazy callbacks queued, and the fourth element is the
>   * total number of callbacks queued.
>   */
> -TRACE_EVENT(rcu_callback,
> +TRACE_EVENT_RCU(rcu_callback,
>  
>  	TP_PROTO(const char *rcuname, struct rcu_head *rhp, long qlen_lazy,
>  		 long qlen),
> @@ -504,7 +508,7 @@
>   * the fourth argument is the number of lazy callbacks queued, and the
>   * fifth argument is the total number of callbacks queued.
>   */
> -TRACE_EVENT(rcu_kfree_callback,
> +TRACE_EVENT_RCU(rcu_kfree_callback,
>  
>  	TP_PROTO(const char *rcuname, struct rcu_head *rhp, unsigned long offset,
>  		 long qlen_lazy, long qlen),
> @@ -539,7 +543,7 @@
>   * the total number of callbacks queued, and the fourth argument is
>   * the current RCU-callback batch limit.
>   */
> -TRACE_EVENT(rcu_batch_start,
> +TRACE_EVENT_RCU(rcu_batch_start,
>  
>  	TP_PROTO(const char *rcuname, long qlen_lazy, long qlen, long blimit),
>  
> @@ -569,7 +573,7 @@
>   * The first argument is the type of RCU, and the second argument is
>   * a pointer to the RCU callback itself.
>   */
> -TRACE_EVENT(rcu_invoke_callback,
> +TRACE_EVENT_RCU(rcu_invoke_callback,
>  
>  	TP_PROTO(const char *rcuname, struct rcu_head *rhp),
>  
> @@ -598,7 +602,7 @@
>   * is the offset of the callback within the enclosing RCU-protected
>   * data structure.
>   */
> -TRACE_EVENT(rcu_invoke_kfree_callback,
> +TRACE_EVENT_RCU(rcu_invoke_kfree_callback,
>  
>  	TP_PROTO(const char *rcuname, struct rcu_head *rhp, unsigned long offset),
>  
> @@ -631,7 +635,7 @@
>   * and the sixth argument (risk) is the return value from
>   * rcu_is_callbacks_kthread().
>   */
> -TRACE_EVENT(rcu_batch_end,
> +TRACE_EVENT_RCU(rcu_batch_end,
>  
>  	TP_PROTO(const char *rcuname, int callbacks_invoked,
>  		 char cb, char nr, char iit, char risk),
> @@ -673,7 +677,7 @@
>   * callback address can be NULL.
>   */
>  #define RCUTORTURENAME_LEN 8
> -TRACE_EVENT(rcu_torture_read,
> +TRACE_EVENT_RCU(rcu_torture_read,
>  
>  	TP_PROTO(const char *rcutorturename, struct rcu_head *rhp,
>  		 unsigned long secs, unsigned long c_old, unsigned long c),
> @@ -721,7 +725,7 @@
>   * The "cpu" argument is the CPU or -1 if meaningless, the "cnt" argument
>   * is the count of remaining callbacks, and "done" is the piggybacking count.
>   */
> -TRACE_EVENT(rcu_barrier,
> +TRACE_EVENT_RCU(rcu_barrier,
>  
>  	TP_PROTO(const char *rcuname, const char *s, int cpu, int cnt, unsigned long done),
>  
> @@ -748,41 +752,6 @@
>  		  __entry->done)
>  );
>  
> -#else /* #ifdef CONFIG_RCU_TRACE */
> -
> -#define trace_rcu_grace_period(rcuname, gp_seq, gpevent) do { } while (0)
> -#define trace_rcu_future_grace_period(rcuname, gp_seq, gp_seq_req, \
> -				      level, grplo, grphi, event) \
> -				      do { } while (0)
> -#define trace_rcu_grace_period_init(rcuname, gp_seq, level, grplo, grphi, \
> -				    qsmask) do { } while (0)
> -#define trace_rcu_exp_grace_period(rcuname, gqseq, gpevent) \
> -	do { } while (0)
> -#define trace_rcu_exp_funnel_lock(rcuname, level, grplo, grphi, gpevent) \
> -	do { } while (0)
> -#define trace_rcu_nocb_wake(rcuname, cpu, reason) do { } while (0)
> -#define trace_rcu_preempt_task(rcuname, pid, gp_seq) do { } while (0)
> -#define trace_rcu_unlock_preempted_task(rcuname, gp_seq, pid) do { } while (0)
> -#define trace_rcu_quiescent_state_report(rcuname, gp_seq, mask, qsmask, level, \
> -					 grplo, grphi, gp_tasks) do { } \
> -	while (0)
> -#define trace_rcu_fqs(rcuname, gp_seq, cpu, qsevent) do { } while (0)
> -#define trace_rcu_dyntick(polarity, oldnesting, newnesting, dyntick) do { } while (0)
> -#define trace_rcu_callback(rcuname, rhp, qlen_lazy, qlen) do { } while (0)
> -#define trace_rcu_kfree_callback(rcuname, rhp, offset, qlen_lazy, qlen) \
> -	do { } while (0)
> -#define trace_rcu_batch_start(rcuname, qlen_lazy, qlen, blimit) \
> -	do { } while (0)
> -#define trace_rcu_invoke_callback(rcuname, rhp) do { } while (0)
> -#define trace_rcu_invoke_kfree_callback(rcuname, rhp, offset) do { } while (0)
> -#define trace_rcu_batch_end(rcuname, callbacks_invoked, cb, nr, iit, risk) \
> -	do { } while (0)
> -#define trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \
> -	do { } while (0)
> -#define trace_rcu_barrier(name, s, cpu, cnt, done) do { } while (0)
> -
> -#endif /* #else #ifdef CONFIG_RCU_TRACE */
> -
>  #endif /* _TRACE_RCU_H */
>  
>  /* This part must be outside protection */
> diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
> index a393e24..2778e44 100644
> --- a/kernel/rcu/rcu.h
> +++ b/kernel/rcu/rcu.h
> @@ -24,11 +24,6 @@
>  #define __LINUX_RCU_H
>  
>  #include <trace/events/rcu.h>
> -#ifdef CONFIG_RCU_TRACE
> -#define RCU_TRACE(stmt) stmt
> -#else /* #ifdef CONFIG_RCU_TRACE */
> -#define RCU_TRACE(stmt)
> -#endif /* #else #ifdef CONFIG_RCU_TRACE */
>  
>  /* Offset to allow for unmatched rcu_irq_{enter,exit}(). */
>  #define DYNTICK_IRQ_NONIDLE	((LONG_MAX / 2) + 1)
> @@ -229,12 +224,12 @@ static inline bool __rcu_reclaim(const char *rn, struct rcu_head *head)
>  
>  	rcu_lock_acquire(&rcu_callback_map);
>  	if (__is_kfree_rcu_offset(offset)) {
> -		RCU_TRACE(trace_rcu_invoke_kfree_callback(rn, head, offset);)
> +		trace_rcu_invoke_kfree_callback(rn, head, offset);
>  		kfree((void *)head - offset);
>  		rcu_lock_release(&rcu_callback_map);
>  		return true;
>  	} else {
> -		RCU_TRACE(trace_rcu_invoke_callback(rn, head);)
> +		trace_rcu_invoke_callback(rn, head);
>  		f = head->func;
>  		WRITE_ONCE(head->func, (rcu_callback_t)0L);
>  		f(head);
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 9180158..d2ad39f 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -2329,14 +2329,14 @@ static void rcu_report_qs_rnp(unsigned long mask, struct rcu_node *rnp,
>   */
>  int rcutree_dying_cpu(unsigned int cpu)
>  {
> -	RCU_TRACE(bool blkd;)
> -	RCU_TRACE(struct rcu_data *rdp = this_cpu_ptr(&rcu_data);)
> -	RCU_TRACE(struct rcu_node *rnp = rdp->mynode;)
> +	bool blkd;
> +	struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
> +	struct rcu_node *rnp = rdp->mynode;
>  
>  	if (!IS_ENABLED(CONFIG_HOTPLUG_CPU))
>  		return 0;
>  
> -	RCU_TRACE(blkd = !!(rnp->qsmask & rdp->grpmask);)
> +	blkd = !!(rnp->qsmask & rdp->grpmask);
>  	trace_rcu_grace_period(rcu_state.name, rnp->gp_seq,
>  			       blkd ? TPS("cpuofl") : TPS("cpuofl-bgp"));
>  	return 0;
> -- 
> 1.8.3.1
> 

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