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Date:   Mon, 14 May 2018 13:29:10 -0700
From:   "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To:     Joe Perches <joe@perches.com>
Cc:     Josh Triplett <josh@joshtriplett.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        Lai Jiangshan <jiangshanlai@gmail.com>,
        Davidlohr Bueso <dave@stgolabs.net>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 18/18] rcu: Use pr_fmt to prefix "rcu: " to logging output
Reply-To: paulmck@linux.vnet.ibm.com
References: <cover.1525964381.git.joe@perches.com>
 <41d9686471d67f6f98d160e5891bf61061515b6d.1525964386.git.joe@perches.com>
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On Thu, May 10, 2018 at 08:45:44AM -0700, Joe Perches wrote:
> Use a consistent logging prefix for all rcu related output.
> 
> Signed-off-by: Joe Perches <joe@perches.com>

I took parts of this (thank you!) but have concerns about other parts.

> ---
>  kernel/rcu/rcu_segcblist.c |  2 ++
>  kernel/rcu/rcuperf.c       | 10 ++++---
>  kernel/rcu/rcutorture.c    | 46 +++++++++++++++----------------
>  kernel/rcu/srcutiny.c      |  2 ++
>  kernel/rcu/srcutree.c      |  5 +++-
>  kernel/rcu/tiny.c          |  3 +++
>  kernel/rcu/tree.c          |  8 +++---
>  kernel/rcu/tree_plugin.h   | 67 +++++++++++++++++++++++++++-------------------
>  kernel/rcu/update.c        | 19 ++++++++-----
>  9 files changed, 96 insertions(+), 66 deletions(-)
> 
> diff --git a/kernel/rcu/rcu_segcblist.c b/kernel/rcu/rcu_segcblist.c
> index 5aff271adf1e..b5f0e7234c4b 100644
> --- a/kernel/rcu/rcu_segcblist.c
> +++ b/kernel/rcu/rcu_segcblist.c
> @@ -20,6 +20,8 @@
>   * Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
>   */
> 
> +#define pr_fmt(fmt) "rcu: " fmt

Given that this file has no printk()s, how is this helping?  Interactions with
WARN_ON() or some such?

> +
>  #include <linux/types.h>
>  #include <linux/kernel.h>
>  #include <linux/interrupt.h>
> diff --git a/kernel/rcu/rcuperf.c b/kernel/rcu/rcuperf.c
> index 076a50fb22ad..ebdd77b45470 100644
> --- a/kernel/rcu/rcuperf.c
> +++ b/kernel/rcu/rcuperf.c
> @@ -19,6 +19,9 @@
>   *
>   * Authors: Paul E. McKenney <paulmck@us.ibm.com>
>   */
> +
> +#define pr_fmt(fmt) "rcu: " fmt

This is going to get us messages of the form "rcu: rcu-perf:", not?
(And other odd combinations, depending on the flavor of RCU under test.)
If so, this does not seem to be an improvement.

> +
>  #include <linux/types.h>
>  #include <linux/kernel.h>
>  #include <linux/init.h>
> @@ -663,12 +666,11 @@ rcu_perf_init(void)
>  			break;
>  	}
>  	if (i == ARRAY_SIZE(perf_ops)) {
> -		pr_alert("rcu-perf: invalid perf type: \"%s\"\n",
> -			 perf_type);
> +		pr_alert("rcu-perf: invalid perf type: \"%s\"\n", perf_type);
>  		pr_alert("rcu-perf types:");
>  		for (i = 0; i < ARRAY_SIZE(perf_ops); i++)
> -			pr_alert(" %s", perf_ops[i]->name);
> -		pr_alert("\n");
> +			pr_cont(" %s", perf_ops[i]->name);
> +		pr_cont("\n");

However, I did take the above changes, good catch!

>  		firsterr = -EINVAL;
>  		goto unwind;
>  	}
> diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
> index 648e1c25707d..45d98ff0d5b8 100644
> --- a/kernel/rcu/rcutorture.c
> +++ b/kernel/rcu/rcutorture.c
> @@ -22,6 +22,7 @@
>   *
>   * See also:  Documentation/RCU/torture.txt
>   */
> +
>  #include <linux/types.h>
>  #include <linux/kernel.h>
>  #include <linux/init.h>
> @@ -908,7 +909,7 @@ rcu_torture_writer(void *arg)
>  	VERBOSE_TOROUT_STRING("rcu_torture_writer task started");
>  	if (!can_expedite)
>  		pr_alert("%s" TORTURE_FLAG
> -			 " GP expediting controlled from boot/sysfs for %s.\n",
> +			 " GP expediting controlled from boot/sysfs for %s\n",
>  			 torture_type, cur_ops->name);
> 
>  	/* Initialize synctype[] array.  If none set, take default. */
> @@ -916,27 +917,27 @@ rcu_torture_writer(void *arg)
>  		gp_cond1 = gp_exp1 = gp_normal1 = gp_sync1 = true;
>  	if (gp_cond1 && cur_ops->get_state && cur_ops->cond_sync) {
>  		synctype[nsynctypes++] = RTWS_COND_GET;
> -		pr_info("%s: Testing conditional GPs.\n", __func__);
> +		pr_info("%s: Testing conditional GPs\n", __func__);
>  	} else if (gp_cond && (!cur_ops->get_state || !cur_ops->cond_sync)) {
> -		pr_alert("%s: gp_cond without primitives.\n", __func__);
> +		pr_alert("%s: gp_cond without primitives\n", __func__);
>  	}
>  	if (gp_exp1 && cur_ops->exp_sync) {
>  		synctype[nsynctypes++] = RTWS_EXP_SYNC;
> -		pr_info("%s: Testing expedited GPs.\n", __func__);
> +		pr_info("%s: Testing expedited GPs\n", __func__);
>  	} else if (gp_exp && !cur_ops->exp_sync) {
> -		pr_alert("%s: gp_exp without primitives.\n", __func__);
> +		pr_alert("%s: gp_exp without primitives\n", __func__);
>  	}
>  	if (gp_normal1 && cur_ops->deferred_free) {
>  		synctype[nsynctypes++] = RTWS_DEF_FREE;
> -		pr_info("%s: Testing asynchronous GPs.\n", __func__);
> +		pr_info("%s: Testing asynchronous GPs\n", __func__);
>  	} else if (gp_normal && !cur_ops->deferred_free) {
> -		pr_alert("%s: gp_normal without primitives.\n", __func__);
> +		pr_alert("%s: gp_normal without primitives\n", __func__);
>  	}
>  	if (gp_sync1 && cur_ops->sync) {
>  		synctype[nsynctypes++] = RTWS_SYNC;
> -		pr_info("%s: Testing normal GPs.\n", __func__);
> +		pr_info("%s: Testing normal GPs\n", __func__);
>  	} else if (gp_sync && !cur_ops->sync) {
> -		pr_alert("%s: gp_sync without primitives.\n", __func__);
> +		pr_alert("%s: gp_sync without primitives\n", __func__);

I used a CDC Cyber 73 in the 1970s.  It had tiny memory by today's
standards, but even it had periods in its error messages.  We can easily
afford them today, especially given that rcutorture is not included in
small-memory Linux configurations.

>  	}
>  	if (WARN_ONCE(nsynctypes == 0,
>  		      "rcu_torture_writer: No update-side primitives.\n")) {
> @@ -1027,7 +1028,7 @@ rcu_torture_writer(void *arg)
>  	WARN_ON_ONCE(can_expedite && rcu_gp_is_expedited());
>  	if (!can_expedite)
>  		pr_alert("%s" TORTURE_FLAG
> -			 " Dynamic grace-period expediting was disabled.\n",
> +			 " Dynamic grace-period expediting was disabled\n",
>  			 torture_type);
>  	rcu_torture_writer_state = RTWS_STOPPING;
>  	torture_kthread_stopping("rcu_torture_writer");
> @@ -1436,7 +1437,7 @@ static int rcu_torture_stall(void *args)
>  			local_irq_disable();
>  		else
>  			preempt_disable();
> -		pr_alert("rcu_torture_stall start on CPU %d.\n",
> +		pr_alert("rcu_torture_stall start on CPU %d\n",
>  			 smp_processor_id());
>  		while (ULONG_CMP_LT(get_seconds(), stop_at))
>  			continue;  /* Induce RCU CPU stall warning. */
> @@ -1445,7 +1446,7 @@ static int rcu_torture_stall(void *args)
>  		else
>  			preempt_enable();
>  		rcu_read_unlock();
> -		pr_alert("rcu_torture_stall end.\n");
> +		pr_alert("rcu_torture_stall end\n");
>  	}
>  	torture_shutdown_absorb("rcu_torture_stall");
>  	while (!kthread_should_stop())
> @@ -1547,10 +1548,10 @@ static int rcu_torture_barrier_init(void)
>  		return 0;
>  	if (cur_ops->call == NULL || cur_ops->cb_barrier == NULL) {
>  		pr_alert("%s" TORTURE_FLAG
> -			 " Call or barrier ops missing for %s,\n",
> +			 " Call or barrier ops missing for %s\n",
>  			 torture_type, cur_ops->name);
>  		pr_alert("%s" TORTURE_FLAG
> -			 " RCU barrier testing omitted from run.\n",
> +			 " RCU barrier testing omitted from run\n",
>  			 torture_type);

And the same for these.

>  		return 0;
>  	}
> @@ -1679,7 +1680,7 @@ static void rcu_torture_err_cb(struct rcu_head *rhp)
>  	 * next grace period.  Unlikely, but can happen.  If it
>  	 * does happen, the debug-objects subsystem won't have splatted.
>  	 */
> -	pr_alert("%s: duplicated callback was invoked.\n", KBUILD_MODNAME);
> +	pr_alert("duplicated callback was invoked\n");
>  }
>  #endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
> 
> @@ -1696,7 +1697,7 @@ static void rcu_test_debug_objects(void)
> 
>  	init_rcu_head_on_stack(&rh1);
>  	init_rcu_head_on_stack(&rh2);
> -	pr_alert("%s: WARN: Duplicate call_rcu() test starting.\n", KBUILD_MODNAME);
> +	pr_alert("WARN: Duplicate call_rcu() test starting\n");
> 
>  	/* Try to queue the rh2 pair of callbacks for the same grace period. */
>  	preempt_disable(); /* Prevent preemption from interrupting test. */
> @@ -1711,11 +1712,11 @@ static void rcu_test_debug_objects(void)
> 
>  	/* Wait for them all to get done so we can safely return. */
>  	rcu_barrier();
> -	pr_alert("%s: WARN: Duplicate call_rcu() test complete.\n", KBUILD_MODNAME);
> +	pr_alert("WARN: Duplicate call_rcu() test complete\n");

I would like to keep these, as they mark the region of console output where
splats are expected.

>  	destroy_rcu_head_on_stack(&rh1);
>  	destroy_rcu_head_on_stack(&rh2);
>  #else /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
> -	pr_alert("%s: !CONFIG_DEBUG_OBJECTS_RCU_HEAD, not testing duplicate call_rcu()\n", KBUILD_MODNAME);
> +	pr_alert("!CONFIG_DEBUG_OBJECTS_RCU_HEAD, not testing duplicate call_rcu()\n");
>  #endif /* #else #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
>  }
> 
> @@ -1740,17 +1741,16 @@ rcu_torture_init(void)
>  			break;
>  	}
>  	if (i == ARRAY_SIZE(torture_ops)) {
> -		pr_alert("rcu-torture: invalid torture type: \"%s\"\n",
> -			 torture_type);
> +		pr_alert("invalid torture type: \"%s\"\n", torture_type);

I am leaving this one...

>  		pr_alert("rcu-torture types:");
>  		for (i = 0; i < ARRAY_SIZE(torture_ops); i++)
> -			pr_alert(" %s", torture_ops[i]->name);
> -		pr_alert("\n");
> +			pr_cont(" %s", torture_ops[i]->name);
> +		pr_cont("\n");

... but taking these.  Good eyes!  (Or scripts, as the case may be.)

>  		firsterr = -EINVAL;
>  		goto unwind;
>  	}
>  	if (cur_ops->fqs == NULL && fqs_duration != 0) {
> -		pr_alert("rcu-torture: ->fqs NULL and non-zero fqs_duration, fqs disabled.\n");
> +		pr_alert("->fqs NULL and non-zero fqs_duration, fqs disabled\n");

This I would like to keep.  Easier to find.

>  		fqs_duration = 0;
>  	}
>  	if (cur_ops->init)
> diff --git a/kernel/rcu/srcutiny.c b/kernel/rcu/srcutiny.c
> index 622792abe41a..9392404cd0fb 100644
> --- a/kernel/rcu/srcutiny.c
> +++ b/kernel/rcu/srcutiny.c
> @@ -21,6 +21,8 @@
>   * Author: Paul McKenney <paulmck@us.ibm.com>
>   */
> 
> +#define pr_fmt(fmt) "rcu: " fmt
> +
>  #include <linux/export.h>
>  #include <linux/mutex.h>
>  #include <linux/preempt.h>
> diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
> index ff894ae6d386..031d2713701f 100644
> --- a/kernel/rcu/srcutree.c
> +++ b/kernel/rcu/srcutree.c
> @@ -26,6 +26,8 @@
>   *
>   */
> 
> +#define pr_fmt(fmt) "rcu: " fmt
> +
>  #include <linux/export.h>
>  #include <linux/mutex.h>
>  #include <linux/percpu.h>
> @@ -390,7 +392,8 @@ void _cleanup_srcu_struct(struct srcu_struct *sp, bool quiesced)
>  		}
>  	if (WARN_ON(rcu_seq_state(READ_ONCE(sp->srcu_gp_seq)) != SRCU_STATE_IDLE) ||
>  	    WARN_ON(srcu_readers_active(sp))) {
> -		pr_info("%s: Active srcu_struct %p state: %d\n", __func__, sp, rcu_seq_state(READ_ONCE(sp->srcu_gp_seq)));
> +		pr_info("%s: Active srcu_struct %p state: %d\n",
> +			__func__, sp, rcu_seq_state(READ_ONCE(sp->srcu_gp_seq)));

I took these.

>  		return; /* Caller forgot to stop doing call_srcu()? */
>  	}
>  	free_percpu(sp->sda);
> diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c
> index a64eee0db39e..52ab205db6e6 100644
> --- a/kernel/rcu/tiny.c
> +++ b/kernel/rcu/tiny.c
> @@ -22,6 +22,9 @@
>   * For detailed explanation of Read-Copy Update mechanism see -
>   *		Documentation/RCU
>   */
> +
> +#define pr_fmt(fmt) "rcu: " fmt
> +
>  #include <linux/completion.h>
>  #include <linux/interrupt.h>
>  #include <linux/notifier.h>
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index effcb898acca..fac633b3aa5e 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -27,6 +27,9 @@
>   * For detailed explanation of Read-Copy Update mechanism see -
>   *	Documentation/RCU
>   */
> +
> +#define pr_fmt(fmt) "rcu: " fmt
> +
>  #include <linux/types.h>
>  #include <linux/kernel.h>
>  #include <linux/init.h>
> @@ -1360,8 +1363,7 @@ static void print_other_cpu_stall(struct rcu_state *rsp, unsigned long gp_seq)
>  	 * See Documentation/RCU/stallwarn.txt for info on how to debug
>  	 * RCU CPU stall warnings.
>  	 */
> -	pr_err("INFO: %s detected stalls on CPUs/tasks:",
> -	       rsp->name);
> +	pr_err("INFO: %s detected stalls on CPUs/tasks:", rsp->name);
>  	print_cpu_stall_info_begin();
>  	rcu_for_each_leaf_node(rsp, rnp) {
>  		raw_spin_lock_irqsave_rcu_node(rnp, flags);
> @@ -3984,7 +3986,7 @@ static void __init rcu_init_geometry(void)
>  	if (rcu_fanout_leaf == RCU_FANOUT_LEAF &&
>  	    nr_cpu_ids == NR_CPUS)
>  		return;
> -	pr_info("RCU: Adjusting geometry for rcu_fanout_leaf=%d, nr_cpu_ids=%u\n",
> +	pr_info("Adjusting geometry for rcu_fanout_leaf=%d, nr_cpu_ids=%u\n",
>  		rcu_fanout_leaf, nr_cpu_ids);

And I took these.

> 
>  	/*
> diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
> index f2dae728c446..7aafff8590d7 100644
> --- a/kernel/rcu/tree_plugin.h
> +++ b/kernel/rcu/tree_plugin.h
> @@ -71,51 +71,62 @@ static bool __read_mostly rcu_nocb_poll;    /* Offload kthread are to poll. */
>  static void __init rcu_bootup_announce_oddness(void)
>  {
>  	if (IS_ENABLED(CONFIG_RCU_TRACE))
> -		pr_info("\tRCU event tracing is enabled.\n");
> +		pr_info("\tRCU event tracing is enabled\n");
>  	if ((IS_ENABLED(CONFIG_64BIT) && RCU_FANOUT != 64) ||
>  	    (!IS_ENABLED(CONFIG_64BIT) && RCU_FANOUT != 32))
>  		pr_info("\tCONFIG_RCU_FANOUT set to non-default value of %d\n",
> -		       RCU_FANOUT);
> +			RCU_FANOUT);

I took this whitespace fix and added the period.

>  	if (rcu_fanout_exact)
> -		pr_info("\tHierarchical RCU autobalancing is disabled.\n");
> +		pr_info("\tHierarchical RCU autobalancing is disabled\n");
>  	if (IS_ENABLED(CONFIG_RCU_FAST_NO_HZ))
> -		pr_info("\tRCU dyntick-idle grace-period acceleration is enabled.\n");
> +		pr_info("\tRCU dyntick-idle grace-period acceleration is enabled\n");
>  	if (IS_ENABLED(CONFIG_PROVE_RCU))
> -		pr_info("\tRCU lockdep checking is enabled.\n");
> +		pr_info("\tRCU lockdep checking is enabled\n");
>  	if (RCU_NUM_LVLS >= 4)
> -		pr_info("\tFour(or more)-level hierarchy is enabled.\n");
> +		pr_info("\tFour(or more)-level hierarchy is enabled\n");
>  	if (RCU_FANOUT_LEAF != 16)
> -		pr_info("\tBuild-time adjustment of leaf fanout to %d.\n",
> +		pr_info("\tBuild-time adjustment of leaf fanout to %d\n",
>  			RCU_FANOUT_LEAF);
>  	if (rcu_fanout_leaf != RCU_FANOUT_LEAF)
> -		pr_info("\tBoot-time adjustment of leaf fanout to %d.\n", rcu_fanout_leaf);
> +		pr_info("\tBoot-time adjustment of leaf fanout to %d\n",
> +			rcu_fanout_leaf);

And this whitespace fix.

>  	if (nr_cpu_ids != NR_CPUS)
> -		pr_info("\tRCU restricting CPUs from NR_CPUS=%d to nr_cpu_ids=%u.\n", NR_CPUS, nr_cpu_ids);
> +		pr_info("\tRCU restricting CPUs from NR_CPUS=%d to nr_cpu_ids=%u\n",
> +			NR_CPUS, nr_cpu_ids);

And I took this (but kept the period), plus used "%s" to make it fit in
80 characters:

	pr_info("\tRCU restricting CPUs from %s=%d to %s=%u.\n",
		"NR_CPUS", NR_CPUS, "nr_cpu_ids", nr_cpu_ids);

>  #ifdef CONFIG_RCU_BOOST
> -	pr_info("\tRCU priority boosting: priority %d delay %d ms.\n", kthread_prio, CONFIG_RCU_BOOST_DELAY);
> +	pr_info("\tRCU priority boosting: priority %d delay %d ms\n",
> +		kthread_prio, CONFIG_RCU_BOOST_DELAY);

I took this but kept the period.

>  #endif
>  	if (blimit != DEFAULT_RCU_BLIMIT)
> -		pr_info("\tBoot-time adjustment of callback invocation limit to %ld.\n", blimit);
> +		pr_info("\tBoot-time adjustment of callback invocation limit to %ld\n",
> +			blimit);
>  	if (qhimark != DEFAULT_RCU_QHIMARK)
> -		pr_info("\tBoot-time adjustment of callback high-water mark to %ld.\n", qhimark);
> +		pr_info("\tBoot-time adjustment of callback high-water mark to %ld\n",
> +			qhimark);
>  	if (qlowmark != DEFAULT_RCU_QLOMARK)
> -		pr_info("\tBoot-time adjustment of callback low-water mark to %ld.\n", qlowmark);
> +		pr_info("\tBoot-time adjustment of callback low-water mark to %ld\n",
> +			qlowmark);
>  	if (jiffies_till_first_fqs != ULONG_MAX)
> -		pr_info("\tBoot-time adjustment of first FQS scan delay to %ld jiffies.\n", jiffies_till_first_fqs);
> +		pr_info("\tBoot-time adjustment of first FQS scan delay to %ld jiffies\n",
> +			jiffies_till_first_fqs);
>  	if (jiffies_till_next_fqs != ULONG_MAX)
> -		pr_info("\tBoot-time adjustment of subsequent FQS scan delay to %ld jiffies.\n", jiffies_till_next_fqs);
> +		pr_info("\tBoot-time adjustment of subsequent FQS scan delay to %ld jiffies\n",
> +			jiffies_till_next_fqs);

And these don't fit even after breaking the line, and I couldn't immediately
come up with a natural way of making them fit, so I left them.  In for a
penny, in for a pound!

>  	if (rcu_kick_kthreads)
> -		pr_info("\tKick kthreads if too-long grace period.\n");
> +		pr_info("\tKick kthreads if too-long grace period\n");
>  	if (IS_ENABLED(CONFIG_DEBUG_OBJECTS_RCU_HEAD))
> -		pr_info("\tRCU callback double-/use-after-free debug enabled.\n");
> +		pr_info("\tRCU callback double-/use-after-free debug enabled\n");
>  	if (gp_preinit_delay)
> -		pr_info("\tRCU debug GP pre-init slowdown %d jiffies.\n", gp_preinit_delay);
> +		pr_info("\tRCU debug GP pre-init slowdown %d jiffies\n",
> +			gp_preinit_delay);
>  	if (gp_init_delay)
> -		pr_info("\tRCU debug GP init slowdown %d jiffies.\n", gp_init_delay);
> +		pr_info("\tRCU debug GP init slowdown %d jiffies\n",
> +			gp_init_delay);
>  	if (gp_cleanup_delay)
> -		pr_info("\tRCU debug GP init slowdown %d jiffies.\n", gp_cleanup_delay);
> +		pr_info("\tRCU debug GP init slowdown %d jiffies\n",
> +			gp_cleanup_delay);
>  	if (IS_ENABLED(CONFIG_RCU_EQS_DEBUG))
> -		pr_info("\tRCU debug extended QS entry/exit.\n");
> +		pr_info("\tRCU debug extended QS entry/exit\n");
>  	rcupdate_announce_bootup_oddness();
>  }
> 
> @@ -133,7 +144,7 @@ static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
>   */
>  static void __init rcu_bootup_announce(void)
>  {
> -	pr_info("Preemptible hierarchical RCU implementation.\n");
> +	pr_info("Preemptible hierarchical RCU implementation\n");
>  	rcu_bootup_announce_oddness();
>  }
> 
> @@ -885,7 +896,7 @@ static struct rcu_state *const rcu_state_p = &rcu_sched_state;
>   */
>  static void __init rcu_bootup_announce(void)
>  {
> -	pr_info("Hierarchical RCU implementation.\n");
> +	pr_info("Hierarchical RCU implementation\n");
>  	rcu_bootup_announce_oddness();
>  }
> 
> @@ -2374,7 +2385,7 @@ void __init rcu_init_nohz(void)
> 
>  	if (!cpumask_available(rcu_nocb_mask) && need_rcu_nocb_mask) {
>  		if (!zalloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL)) {
> -			pr_info("rcu_nocb_mask allocation failed, callback offloading disabled.\n");
> +			pr_info("rcu_nocb_mask allocation failed, callback offloading disabled\n");
>  			return;
>  		}
>  	}
> @@ -2387,17 +2398,17 @@ void __init rcu_init_nohz(void)
>  #endif /* #if defined(CONFIG_NO_HZ_FULL) */
> 
>  	if (!cpumask_subset(rcu_nocb_mask, cpu_possible_mask)) {
> -		pr_info("\tNote: kernel parameter 'rcu_nocbs=', 'nohz_full', or 'isolcpus=' contains nonexistent CPUs.\n");
> +		pr_info("\tNote: kernel parameter 'rcu_nocbs=', 'nohz_full', or 'isolcpus=' contains nonexistent CPUs\n");
>  		cpumask_and(rcu_nocb_mask, cpu_possible_mask,
>  			    rcu_nocb_mask);
>  	}
>  	if (cpumask_empty(rcu_nocb_mask))
> -		pr_info("\tOffload RCU callbacks from CPUs: (none).\n");
> +		pr_info("\tOffload RCU callbacks from CPUs: (none)\n");
>  	else
> -		pr_info("\tOffload RCU callbacks from CPUs: %*pbl.\n",
> +		pr_info("\tOffload RCU callbacks from CPUs: %*pbl\n",
>  			cpumask_pr_args(rcu_nocb_mask));
>  	if (rcu_nocb_poll)
> -		pr_info("\tPoll for callbacks from no-CBs CPUs.\n");
> +		pr_info("\tPoll for callbacks from no-CBs CPUs\n");
> 
>  	for_each_rcu_flavor(rsp) {
>  		for_each_cpu(cpu, rcu_nocb_mask)

Other than that, I kept the periods.

> diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
> index 4c230a60ece4..e6ccf4864fe6 100644
> --- a/kernel/rcu/update.c
> +++ b/kernel/rcu/update.c
> @@ -30,6 +30,9 @@
>   *		http://lse.sourceforge.net/locking/rcupdate.html
>   *
>   */
> +
> +#define pr_fmt(fmt) "rcu: " fmt
> +
>  #include <linux/types.h>
>  #include <linux/kernel.h>
>  #include <linux/init.h>
> @@ -844,9 +847,10 @@ static void __init rcu_tasks_bootup_oddness(void)
>  {
>  #ifdef CONFIG_TASKS_RCU
>  	if (rcu_task_stall_timeout != RCU_TASK_STALL_TIMEOUT)
> -		pr_info("\tTasks-RCU CPU stall warnings timeout set to %d (rcu_task_stall_timeout).\n", rcu_task_stall_timeout);
> +		pr_info("\tTasks-RCU CPU stall warnings timeout set to %d (rcu_task_stall_timeout)\n",
> +			rcu_task_stall_timeout);
>  	else
> -		pr_info("\tTasks RCU enabled.\n");
> +		pr_info("\tTasks RCU enabled\n");
>  #endif /* #ifdef CONFIG_TASKS_RCU */
>  }
> 
> @@ -945,15 +949,16 @@ void rcu_early_boot_tests(void) {}
>  void __init rcupdate_announce_bootup_oddness(void)
>  {
>  	if (rcu_normal)
> -		pr_info("\tNo expedited grace period (rcu_normal).\n");
> +		pr_info("\tNo expedited grace period (rcu_normal)\n");
>  	else if (rcu_normal_after_boot)
> -		pr_info("\tNo expedited grace period (rcu_normal_after_boot).\n");
> +		pr_info("\tNo expedited grace period (rcu_normal_after_boot)\n");
>  	else if (rcu_expedited)
> -		pr_info("\tAll grace periods are expedited (rcu_expedited).\n");
> +		pr_info("\tAll grace periods are expedited (rcu_expedited)\n");
>  	if (rcu_cpu_stall_suppress)
> -		pr_info("\tRCU CPU stall warnings suppressed (rcu_cpu_stall_suppress).\n");
> +		pr_info("\tRCU CPU stall warnings suppressed (rcu_cpu_stall_suppress)\n");
>  	if (rcu_cpu_stall_timeout != CONFIG_RCU_CPU_STALL_TIMEOUT)
> -		pr_info("\tRCU CPU stall warnings timeout set to %d (rcu_cpu_stall_timeout).\n", rcu_cpu_stall_timeout);
> +		pr_info("\tRCU CPU stall warnings timeout set to %d (rcu_cpu_stall_timeout)\n",
> +			rcu_cpu_stall_timeout);
>  	rcu_tasks_bootup_oddness();
>  }

And I kept these periods.  Please see below for updated patch.

							Thanx, Paul

------------------------------------------------------------------------

commit 7b88a0fd75ae1f4a018a315d1e9ffcdbfc6c8e6f
Author: Joe Perches <joe@perches.com>
Date:   Mon May 14 13:27:33 2018 -0700

    rcu: Use pr_fmt to prefix "rcu: " to logging output
    
    This commit also adjusts some whitespace while in the area.
    
    Signed-off-by: Joe Perches <joe@perches.com>
    Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

diff --git a/kernel/rcu/rcuperf.c b/kernel/rcu/rcuperf.c
index 479820d231bf..9047e5439e46 100644
--- a/kernel/rcu/rcuperf.c
+++ b/kernel/rcu/rcuperf.c
@@ -663,12 +663,11 @@ rcu_perf_init(void)
 			break;
 	}
 	if (i == ARRAY_SIZE(perf_ops)) {
-		pr_alert("rcu-perf: invalid perf type: \"%s\"\n",
-			 perf_type);
+		pr_alert("rcu-perf: invalid perf type: \"%s\"\n", perf_type);
 		pr_alert("rcu-perf types:");
 		for (i = 0; i < ARRAY_SIZE(perf_ops); i++)
-			pr_alert(" %s", perf_ops[i]->name);
-		pr_alert("\n");
+			pr_cont(" %s", perf_ops[i]->name);
+		pr_cont("\n");
 		firsterr = -EINVAL;
 		goto unwind;
 	}
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index ba82285a023a..9d80245b2a1c 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -1744,8 +1744,8 @@ rcu_torture_init(void)
 			 torture_type);
 		pr_alert("rcu-torture types:");
 		for (i = 0; i < ARRAY_SIZE(torture_ops); i++)
-			pr_alert(" %s", torture_ops[i]->name);
-		pr_alert("\n");
+			pr_cont(" %s", torture_ops[i]->name);
+		pr_cont("\n");
 		firsterr = -EINVAL;
 		goto unwind;
 	}
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index ff894ae6d386..031d2713701f 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -26,6 +26,8 @@
  *
  */
 
+#define pr_fmt(fmt) "rcu: " fmt
+
 #include <linux/export.h>
 #include <linux/mutex.h>
 #include <linux/percpu.h>
@@ -390,7 +392,8 @@ void _cleanup_srcu_struct(struct srcu_struct *sp, bool quiesced)
 		}
 	if (WARN_ON(rcu_seq_state(READ_ONCE(sp->srcu_gp_seq)) != SRCU_STATE_IDLE) ||
 	    WARN_ON(srcu_readers_active(sp))) {
-		pr_info("%s: Active srcu_struct %p state: %d\n", __func__, sp, rcu_seq_state(READ_ONCE(sp->srcu_gp_seq)));
+		pr_info("%s: Active srcu_struct %p state: %d\n",
+			__func__, sp, rcu_seq_state(READ_ONCE(sp->srcu_gp_seq)));
 		return; /* Caller forgot to stop doing call_srcu()? */
 	}
 	free_percpu(sp->sda);
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 23b855f5c5cb..3826ce90fd6e 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -27,6 +27,9 @@
  * For detailed explanation of Read-Copy Update mechanism see -
  *	Documentation/RCU
  */
+
+#define pr_fmt(fmt) "rcu: " fmt
+
 #include <linux/types.h>
 #include <linux/kernel.h>
 #include <linux/init.h>
@@ -1352,8 +1355,7 @@ static void print_other_cpu_stall(struct rcu_state *rsp, unsigned long gp_seq)
 	 * See Documentation/RCU/stallwarn.txt for info on how to debug
 	 * RCU CPU stall warnings.
 	 */
-	pr_err("INFO: %s detected stalls on CPUs/tasks:",
-	       rsp->name);
+	pr_err("INFO: %s detected stalls on CPUs/tasks:", rsp->name);
 	print_cpu_stall_info_begin();
 	rcu_for_each_leaf_node(rsp, rnp) {
 		raw_spin_lock_irqsave_rcu_node(rnp, flags);
@@ -3996,7 +3998,7 @@ static void __init rcu_init_geometry(void)
 	if (rcu_fanout_leaf == RCU_FANOUT_LEAF &&
 	    nr_cpu_ids == NR_CPUS)
 		return;
-	pr_info("RCU: Adjusting geometry for rcu_fanout_leaf=%d, nr_cpu_ids=%u\n",
+	pr_info("Adjusting geometry for rcu_fanout_leaf=%d, nr_cpu_ids=%u\n",
 		rcu_fanout_leaf, nr_cpu_ids);
 
 	/*
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 54a251640f53..9a28ba2755b9 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -74,8 +74,8 @@ static void __init rcu_bootup_announce_oddness(void)
 		pr_info("\tRCU event tracing is enabled.\n");
 	if ((IS_ENABLED(CONFIG_64BIT) && RCU_FANOUT != 64) ||
 	    (!IS_ENABLED(CONFIG_64BIT) && RCU_FANOUT != 32))
-		pr_info("\tCONFIG_RCU_FANOUT set to non-default value of %d\n",
-		       RCU_FANOUT);
+		pr_info("\tCONFIG_RCU_FANOUT set to non-default value of %d.\n",
+			RCU_FANOUT);
 	if (rcu_fanout_exact)
 		pr_info("\tHierarchical RCU autobalancing is disabled.\n");
 	if (IS_ENABLED(CONFIG_RCU_FAST_NO_HZ))
@@ -88,11 +88,14 @@ static void __init rcu_bootup_announce_oddness(void)
 		pr_info("\tBuild-time adjustment of leaf fanout to %d.\n",
 			RCU_FANOUT_LEAF);
 	if (rcu_fanout_leaf != RCU_FANOUT_LEAF)
-		pr_info("\tBoot-time adjustment of leaf fanout to %d.\n", rcu_fanout_leaf);
+		pr_info("\tBoot-time adjustment of leaf fanout to %d.\n",
+			rcu_fanout_leaf);
 	if (nr_cpu_ids != NR_CPUS)
-		pr_info("\tRCU restricting CPUs from NR_CPUS=%d to nr_cpu_ids=%u.\n", NR_CPUS, nr_cpu_ids);
+		pr_info("\tRCU restricting CPUs from %s=%d to %s=%u.\n",
+			"NR_CPUS", NR_CPUS, "nr_cpu_ids", nr_cpu_ids);
 #ifdef CONFIG_RCU_BOOST
-	pr_info("\tRCU priority boosting: priority %d delay %d ms.\n", kthread_prio, CONFIG_RCU_BOOST_DELAY);
+	pr_info("\tRCU priority boosting: priority %d delay %d ms.\n",
+		kthread_prio, CONFIG_RCU_BOOST_DELAY);
 #endif
 	if (blimit != DEFAULT_RCU_BLIMIT)
 		pr_info("\tBoot-time adjustment of callback invocation limit to %ld.\n", blimit);